The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format. Except when it’s interrupted by a massive writing project, then it’s not every week.

But by special request, here’s the first of several revolver cartridges, which have been sadly neglected on The Reloading Press to date.

.357 Magnum (9x33mmR)



The .357 Magnum was developed in 1934, and the first weapon to chamber it was released in 1935. It was developed in response to the .38 Super (which incidentally was found to penetrate the bulletproof  – bullet-resistant, thanks – vests of the day. That required a faster bullet, as those vests were proof against anything slower than 1,000 fps).

Well, the .357 would eventually far, far eclipse this. More on that in a moment. 

Regardless, this is a very high energy cartridge, and the pressure is about double that of the .38 Special that was the foundation of the design. This led to the case being lengthened by about 3mm to prevent being able to close the cylinder on .38 Special revolvers accidentally loaded with .357M cartridges, which can be counted on to have very poor outcomes to the weapon and the shooter.

The .357 and .38 cartridges both fire 9.07mm bullets (actually .355 to .357″); the .38″ refers to a naming convention used for the outside diameter of the cartridge case.

In any case, this for a long while was the standard reference cartridge by which – rightly or wrongly – all other self-defense and law enforcement cartridges were judged. You can see this in many period writings, and even the more-recent .357 SIG hearkens back to the power (and given the loading below, that is both literal and advertising power) of the .357M harnessed in a conveniently sized automatic platform.

But there’s no question: the .357 is a powerhouse, and revolvers chambered in it with barrel lengths from 4″ to 8″ are bad news if you’re on the wrong end of them. The power is such that they made somewhat-attractive snub-nosed backup guns as well, though having fired one myself, for this purpose a small-frame 9mm is probably a better choice. More on that later.
Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 101.6mm (4″) for the (test) barrel length.

INPUT
125gr .357M
Chamber
Pressure
35000 psi
Barrel
bore
9.1 mm
Case
Length
33 mm
Chamber
Bore
9.1 mm
Barrel
length
101.6 mm
Bullet
Mass
125 grains
Aspect
Ratio
1.7 L/Bore
Burn
length
40 mm
Projectile
Caliber
9.1 mm
Total
Accelerated Mass
125 grains
Expansion
Ratio
1.95 expansion
Projectile
Load
1



Output Stats


The .357M has a lot of chamberings available for it. Everything from about 7 to 12 grams (110 to 158 gr), with the most common seeming to be 125gr and 158gr. Both are available in a wide variety of energy ranges, and some of those energies are shockingly high. The highest energy projectile found develops 1,700fps out of a 4″ barrel. The military 9mm is 124gr and develops 1,250fps out of a 5″ barrel. So yeah, it’s a monster. 

As per usual, I selected the biggest and baddest load to do GURPS stats of, because players will usually gravitate towards this.

Notes

  • The velocity is at the muzzle. The velocity with a 4″ (101.6mm) test barrel is tuned to match real-world data at 1700fps with a 124gr JHP bullet. This might not be the very highest energy .357 available, but it’s likely close.
  • Velocity out of shorter than a 2″ barrel falls off dramatically – you can lose 1d per 2mm of barrel in this range. 
  • The bulk of a .357 cylinder would suggest perhaps going with the 9mm or similar loads actually tuned to deliver performance out of a shorter barrel.
  • I very strongly suspect that the “tipping point” where the propellant charge no longer accelerates the bullet falls rather lower than the 6d damage shown here. This site, “Ballistics by the inch,” shows a 125gr .357M getting the best velocity out of a 16″ barrel, falling from 2000fps down to 1740fps by adding 2″ of barrel. So cutting off damage increases past 16″ of barrel is probably legit.
The very, very good results from 3″ to 16″ barrels make the .357M a versatile cartridge, especially in situations where carrying more than one type is impractical for whatever reason. 

The very, very good results are also a direct result of taking the highest energy I could find. A more reasonable 125gr projectile that is tuned to 1450fps from a 4″ barrel, or a 158gr hunting load at about 1250fps (9mm velocity with a heavier bullet) will both deliver about 3d damage from a 4″ barrel, a 15% reduction. The lower powder burn length required in the model will also tend to tap out the velocity at lower barrel lengths as well.

The JHP with modern design is quite impressive, expanding in this case to 1.95x its starting diameter, or about  17mm – enough to legitimately earn a pi++ modifier. Damage falls to 2d+1 in the model, but 2d+1 pi++ is nothing to sneeze at, being both more penetrating and equally expanding as a .45ACP.

GURPS rules don’t allow that, but the same bullet would do 3d (0.5) pi+. 

So my model would predict 8 points of penetration, and 16 points of injury. GURPS RAW would be 5.25 points of penetration, 15.75 points of injury for the JHP bullets, compared to a flat 10.5 points of penetration and injury for FMJ rounds.

Platforms


The platforms here can be summarized quickly. Sub-nosed revolvers, moderate-barrel revolvers, big-honkin’ barrel revolvers, one or two insane semi-automatic pistols, and lever action carbines.

Starting with the rifle, you can expect a 16″ barrel and 8-round or 10-round capacity, and probably Acc 4 from this. It’s handy and will allow you to get the most possible velocity out of the very effective .357M.

Next comes the semi-auto, which is basically either a 1911-style frame (Coonan sells one), or the venerable and oft-discussed Desert Eagle. We’ve seen the DE before, so I’ll find a picture of the Coonan.

Lastly, we have revolvers in various frame sizes and barrel lengths. The manufacturers (S&W itself in the image shown) have done a nice job of giving options from “beefy” to “svelte.”

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

10mm Auto (10x25mm)



The 10mm was designed by none other than Colonel Jeff Cooper. Created to be a flatter shooting cartridge than the .45 ACP but hit harder and wound better than the 9mm. When you take a projectile that is substantially heavier than the 9mm, larger diameter, and have the audacity to throw it 100fps faster as well, success is a foregone conclusion.

At least by that metric. Undoubtedly a powerful cartridge – the heavier loads outthwack a .357M – it earns its power by being large, kicking hard, and being generally hard to control. The same problems that exist with large autos in .44M or even the mighty .50AE but on a smaller scale.

The cartridge’s power drew the attention of the FBI in the wake of the famous Miami shootout, and the cartridge was selected as the standard FBI chambering in the S&W 1076 in 1989. The amazing recoil and large pistol size resulted in the creation of the .40S&W a scant year later.

Certain agencies still use the 10mm, and given the round’s power, it’s not a surprise. That being said, if you’re going to load up with an SMG that shoots a 10mm bullet, you will probably get at least as much oomph out of a 5.56mm or 6.8mm carbine as well.
Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 117mm for the (test) barrel length.

INPUT
180gr 10mm Auto
Chamber Pressure 37500 psi
Barrel bore 10 mm
Case Length 25 mm
Chamber Bore 10 mm
Barrel length 117 mm
Bullet Mass 180 grains
Aspect Ratio 1.8 L/Bore
Burn length 11.6 mm
Projectile Caliber 10 mm
Total Accelerated Mass 180 grains
Expansion Ratio 1.78 expansion
Projectile Load 1

Output Stats

The 10mm Auto is kind of a beast. Sure, it’s not a .44M, mostly. But it’s very powerful, and as there are very few reasons not to carry the most energetic load if you’re carrying one of these at all, I elected to pick more or less the same 180gr bullet used in my .40S&W example, but fired quite a bit faster.

Notes

  • The velocity is at the muzzle. The velocity with a 4.6″ (117mm) test barrel is tuned to match real-world data at 1350fps with a 180gr JHP bullet. This is not the highest energy 10mm available, but it’s pretty close. It gives a good comparison to a .40 on steroids.
  • The breakpoint for pi+ in GURPS is currently at 10mm/.40″. You can see that’s a bit generous, as the bullet modeled would be better at closer to +1 per die. Still, because of that breakpoint, 10mm bullets hit a sweet spot.
Some more notes on barrel length. There are really two practical lengths for pistols here. The 3-4″ set will deliver 3d damage. A full-sized pistol with a 4.5-5″ barrel hits 3d+1. SMG barrels between 6.5 and 9.5″ long will get 4d-1. Unlike the .40, the 10mm continues to gain a bit in damage, with a 9.7-14.5″ barrel turning in 4d. A 16-20″ rifle will hit 4d+1, but beyond that you are into very long weapons.

The JHP with modern design is quite impressive, expanding in this case to 1.77x its starting diameter – and there are commercially-available loads that will expand to a full 2x the starting diameter. The standard load with the 1.78x expansion has an amazing calculated wound channel modifier of 2.4x, making the damage with this load out of a 117mm barrel 2d+2 {2.4} pi, or 3d+1 (0.5) pi++ using RAW. That’s considerably more injury out of a handgun than many or even most 9mm SMGs.

Alternate Loads

If you don’t go heavy and fairly fast, you can go light and ridiculously so. One of the more energetic loads is a 155gr projectile at a blistering 1500fps. This doesn’t really change the stats.

Platforms

For a cartridge that faced very rapid obsolescence at the hands of the .40 “Short and Wimpy”, after the first purpose-built Bren Ten handguns came out, there were a substantial number of quality follow-ons. The Colt Delta Elite and Smith 1076 were big in this chambering, and Glock released their Glock 20 and smaller Glock 29 in 10mm. Both of these were quite large-frame handguns, but in general if you could grip their double-stack .45ACP (the Glock 21), you could hold and shoot their 10mm.

You can get high end firearms in 10mm from such luminaries as Kimber (bout $1,000) or STI ($1600), and these are mostly built on heavy, steel, 1911-style frames.

For SMGs, you seem to have the MP5/10 by H&K, and the MP5/10 by H&K. Seriously. With the right ammo (the fast, light load above) you will still get 4d (0.5) pi++ out of the 225mm barrel, which ain’t all bad.

More pix follow.

The GURPS rules for hollow point or expanding bullets in GURPS are pretty simple: you pick up one level of increased wounding modifier in exchange for having an armor divisor of (0.5), meaning that your projectile is really quite poor at penetrating armor, but pretty good at injuring people.

So 2d+1 (0.5) pi- would normally average 8 points of penetration through armor, and 4 points of injury on an unarmored person. Against DR 4, on the average it would be blocked. Why one would fire off a pi- hollow-point is beyond me, of course – the example just shows how the rules work.

A 9mm FMJ would be 2d+2 pi normally, and thus do 9 points of armor penetration, 9 points of injury, and 5 injury through DR 4. A 9mm hollowpoint would (in RAW GURPS) would punch through only DR 4.5 on the average, and do 13.5 points of injury against an unarmed person. Only one point (on the average) would punch through DR 4, resulting in 1.5 injury.

A .45 ACP would normally do 2d pi+, and in hollowpoint will do 2d (0.5) pi++. So again, against an unarmored person, 7 points of penetration and 10.5 of inury in ball, and 14 in hollow point. Through DR 4, 7 won’t penetrate in JHP, but ball will do 4.5 injury.

In any case, the RAW is simple.


The Ballistic Calculator


My ballistics calculator handles things a bit differently. It recalculates penetration based on the expanded diameter of the projectile instead of applying arbitrary modifiers. This can produce truly monstrous wound channel modifier (though GURPS caps at pi++), but also gives a nice, straightforward damage reduction that isn’t quite as harsh as the (0.5) armor divisor.

Now, let’s look at three examples. A 1.3 expansion (typical of some .45ACP), a 2.0 expansion (which is typical of Jacketed Soft Point rifle bullets), and 1.65 (which works well for modern 9mm and .40 S&W that was engineered for large expansion).

  • A .45 ACP with no expansion has 2d with a 1.5 modifer. (7 points)
  • A .45 ACP wth a 1.3 expansion has 1d+3 with a 2.1 modifer (6.5 points, or )
  • A .45 ACP with a 1.65 expansion has 1d+2 with a 2.7 modifier (5.5 points, or -22%)
  • A .45 ACP with a 2.0 expansion also does 1d+2 with a 3.4 modifier

A 6.8x43mm would do 6d with a 0.7 modifier unexpanded

  • The 6.8 with a 1.3 expansion would do 5d+2 with a 0.9 (21 to 19.5, or -7%)
  • The 6.8 with a 1.65 expansion would do 5d with a 1.2 (21 to 17.5, or -17%)
  • The 6.8 with a 2.0 expansion would do 4d+3 with a 1.5 (21 to 17, or -19%)
So between soft and expanded, you’re looking at about -20% for effective hollow-points. That’s about -1.5 per 2d damage, regardless of caliber. If you want to account for soft bullets, it’s more like a (0.8) than (0.5).
So a 9mm would go to 2d pi+, and a 6.8mm would be 6d-4.5, which is 5d-1 pi+.
Against armor, it will tend to do a bit better than the RAW, but still worse than unarmored flesh.
The (0.8) will be annoying in play; I’d tend to ditch it, but if you can quickly just increase DR by 25% before figuring penetration, you’re good. 5d-1 pi+ carbine bullet vs DR 12? It becomes DR 15, and likely on the average will do 1.5 penetration, increasing to a bit over 2 points of injury on the average. By RAW, it’s 6d (0.5) pi+, and DR 12 goes to DR 24, and will almost always bounce.

Parting Shot

This is for extreme realism fans, and even so, the modeling work required to pull this off is probably more than most people need. But the RAW really nerfs the penetration abilities of JHP bullets, making them devastating against
unarmored targets, but utterly useless against any sort of armor. That’s true to an extent, but not as much as GURPS makes it. 

The trade-off is a lower DR increase relative to RAW, but also just slightly lower raw penetration (which takes the edge off the larger wound modifiers when not using the granular, limited nature of the pi-/pi/pi+/pi++ scale.
For games, the RAW is, without a doubt, easier. The math-heavy version makes for better comparisons where The Reloading Press is concerned. 

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

.45 ACP / 11.43 x 23mm

The .45 ACP was designed and adopted between 1910 and achieved “final” approval in 1911, when mated with the winner of the platform competition, the now-legendary Colt M1911. Adopted as a result of reported failures to incapacitate the enemy in the Phillipine-American War (the Moro Rebellion) from both the .38 Long Colt and the .30-40 Krag. A bigger bullet with a bigger punch was requested, and this cartridge was modified from a .41-caliber cartridge then under current development by Colt and Browning. 

The basic inputs will be driven from the classic load – the 230gr full metal jacket round that formed the basic projectile more than a century ago. Fired from a 5″ barrel at 250fps, this is in many ways the standard against which all other bullets are compared – if that standard isn’t the 9mm. And if it is, the proponents of the .45ACP are willing to fight them about it.
Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 127mm for the (test) barrel length.

INPUT
.45 ACP
Chamber Pressure 18575 psi
Barrel bore 11.43 mm
Case Length 23 mm
Chamber Bore 11.43 mm
Barrel length 127 mm
Bullet Mass 230 grains
Aspect Ratio 1.5 L/Bore
Burn length 5.5 mm
Projectile Caliber 11.43 mm
Total Accelerated Mass 230 grains
Expansion Ratio 1.7 expansion
Output Stats

The classic cartridge is the original one: the 230gr load which earns the standard GURPS stats of 2d pi+ when fired from the 5″ barrel of the Colt M1911. You can see that the half-damage range is healthy, and that barrel length starts to be substantial in order to eke out more energy from the round.

Notes
  • The velocity is at the muzzle. The velocity with a 5″ (127mm) test barrel is tuned to match real-world data at 830 fps with a 230gr FMJ bullet. This is not the highest energy .45 available, but it’s the standard. 
  • The 230gr bullets have a straight-up pi+ modifier (AP modifier of 1.5) in my model; 185gr are 1.43 and 200gr is 1.46. So pi+ is the rule of the day
Once you get past a 15″ barrel, you’re not helping yourself. At all. So in effect there are three practical barrel lengths for GURPS: 3.2 to 5″ are all in the 2d range. SMG barrels of up to 11″ will get 2d+1. And then carbine-length barrels of 16-18″ will do 3d-1. The intermediate 11-15″ range, while interesting from a GURPS perspective, seems to be a bit of a no-man’s land.

The default original cartridge was a full-metal jacket round. The modern tendency for self-defense pistols tends to be Jacketed Hollow Point, or JHP. These can have some impressive expanded diameters . . . but not that much more than the .40S&W, which makes it a non-issue to trade higher magazine capacity for expanded diameter when dealing with modern rounds.

Not that a 0.7″ to 0.75″ expanded diameter is chicken feed, and the highest expanding load is larger than that of the highest .40 . . . but only by 0.03″.

Alternate Loads

The load chosen for the original was the original. But there are some interesting and impressive hollow-point loads. 

From a GURPS perspective, though . . . the best you can get from a hollow point is pi++. Now, that’s impressive, but you don’t need that much of an expanded diameter to get there, so the really high expansions, while great (perhaps) in the real world, don”t buy you much. From that perspective, the “ultimate” JHP is going to be the highest energy load you can buy that ekes out the full pi++ when expanded. That’s only about 0.59″ with the 200 and 230gr bullets, and 0.60 for the 185gr. All of that means that the bullets on the list below all qualify for a “good” GURPS JHP.

Of the list below, the fastest 230gr load is 908  fps, the fastest 200gr is 982, and the fastest 185gr is 1019. These produce (including proper expansion multiples):

  • 230gr at 908 fps: 2d pi++
  • 200gr at 982 fps: 2d pi++
  • 185gr at 1019 fps: 2dpi++

Recall my model accounts for the JHP not with an armor divisor (in this case a multiplier), but a damage reduction for raw penetration. This basically means that any shooter worth their salt will carry JHP rounds at the full 2d out of a 5″ barrel, and they basically all perform close enough to the same that you don’t need to specify which one you’re using.

Not too many people seem to make high-energy FMJ rounds that aren’t mostly less than 100 grains, so cataloging them isn’t worthwhile. 

Platforms


M1991

The number of .45ACP handguns is vast, vast, vast, but of course you have to start with the actual Colt .45 ACP, now updated as the Colt M1991. This venerable design is also built by a large number of custom pistol shops, such as Kimber, who adds plenty of quality at a reasonable price, and there are other custom shops that do fantastic work (for a high price). Les Baer, Guncrafter Industries, Wilson Combat, Ed Brown, and STI (whose pistols were given to Monster Hunter Owen Pitt as a gift). 

STI Lawman

These tend to be single-stack firearms of the original 7 or 8-round capacity. Larger capacity magazines can be found for those with suitably-larger hands. The Glock 21 held 13 rounds, and other double-stack magazines from 10 to 14 rounds capacity can be had for Sig Sauer, Para-Ordnance, and others. Some of these are available in cut-down versions with shorter barrels for concealability.

In the SMG set, the Kriss makes a unique SMG designed from the ground up to be ridiculously low recoil, and the inevitable H&K SMG – the UMP chambered for .45ACP.

And of course, the original .45 Thompson cannot be left out – both in “gangster” configuration with drum magazines, or the military issue SMG seen in Saving Private Ryan and other movies with stick mags.

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

.40 S&W / 10x22mm S&W

.40 Flat-nose FMJ

The .40S&W was invented after the 9mm bullets that were the standard issue for FBI agents failed to perform as desired during the infamous 1986 Miami shootout. The detals of that are interesting but not pertinent, other than it led to the trial and search for a replacement.

Initially, a 10mm Auto was selected, butt that made for a large-frame pistol and packed a pretty significant whollop. Having personally shot a 10mm, I can attest to this – it’s a handful.

During ballistic tests, it was found that a 10mm 180gr projectile loaded to about 950fps met the criteria for wound channel and penetration depth. That left a lot of air in the 10x25mm (10mmAuto) case, so downsizing it to 10x22mm let the package fit into a 9mm pistol frame. The cartridge debuted in January 1990.

The basic inputs will be driven from a 180gr JHP bullet that matches the standard projectile initially developed for the FBI, selected as a higher energy load that expands well. This provides a healthy energy load . . . but not the most energetic available (which GURPS favors due to conversion factors).

Precis – The Reloading Press weekly feature writes up the .40S&W pistol cartridge.

Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 100mm for the (test) barrel length.

INPUT
.40S&W
Chamber Pressure 34000
Barrel bore 10
Case Length 21
Chamber Bore 10
Barrel length 100
Bullet Mass 180
Aspect Ratio 1.8
Burn length 3.81
Projectile Caliber 10
Total Accelerated Mass 180
Expansion Ratio 1.78
Projectile Load 1

Output Stats

Selected Gel Impact Tracks

This cartridge is designed to be an intermediate in many ways. Intermediate in caliber between 9mm and .45ACP, intermediate in velocity between the 1250fps of the 9mm and the 800fps of the standard .45 ACP.

This one is a 180gr projetile at 995 fps out of a 100mm barrel, which will do even better out of the 5″ full-sized pistol. More on that later, but here’s the chart showing how damage changes with barrel length.

Notes
  • The velocity is at the muzzle. The velocity with a 4″ (100mm) test barrel is tuned to match real-world data at 995 fps with a 180gr JHP bullet. This is not the highest energy .40 available, but it’s pretty good, and within the original FBI specs, so it’s what I chose.
  • Out of a full-sized, 5″ barrel such as the M9 pistol (Beretta M92, or M96 when it’s in .40) there’s no real reason to use a 9mm in GURPS. More on that later.
  • The breakpoint for pi+ in GURPS is currently at 10mm/.40″. You can see that’s a bit generous, as the bullet modeled would be better at closer to +1 per die.
Some more notes on barrel length. There are really two practical lengths for pistols here. The 3-4″ set will deliver 2d+1 damage. The full-sized pistol with a 5″/127mm barrel hits 2d+2. SMG barrels between 6.5 and 11″ long will get 3d-1. After that, carbine-length barrels will eke out 3d.

The JHP with modern design is quite impressive, expanding in this case to 1.77x its starting diameter – and there are commercially-available loads that will expand to a full 2x the starting diameter, though they’re slightly slower. With the model the less-expanding and faster one is better, though. That will do 2d with  calculated 2.4 wound channel modifier. That won’t translate into usable criteria in 4e, as damage tops out at pi++. Still, most .40 weapons will hold 10-13 rounds in a concealable, accurate package that will do 2d pi++, getting the penetration of a 9mm JHP (2d) but the wounding of a .45 ACP JHP (pi++).

Alternate Loads

As noted earlier, the load chosen isn’t the only load, nor is it the “best” from a GURPS conversion standpoint. There are some very impressive loads in JHP (typical self-defense loads, but not military style stuff) in the table below.

The hottest load will do 2d+2 even out of a 4″ barrel, expands to 1.65x (0.66″), and hits the right breakpoints to get 2d+1 pi++ out of a JHP. That’s about as good as you can eke out of a hollow-point round.

Penetration in gelatin of various commercial JHP rounds

In the FMJ category, there are some hot, hot loads out there that require  fully-supported chamber to fire properly. The Glock 22 and 23, for example, were partially supported, and could do nasty things with this ammo.

But if you have the right platform, there are 155gr bullets that zip along at 1300fps (3d), and a very fast 135gr bullet at 1500fps that also does 3d, but is light-weight enough to drop from 1.2 to 1.1, which drops it out of any contention for pi+.

Platforms

Springfield XD(M) with extended mag

There are a huge number of handguns chambered for the .40S&W – it rapidly became one of the most, if not the most, popular chambering for self-defense and law-enforcement weapons – at least recently and in the USA.

Pocket pistols with a 3″ barrel such as the S&W M&P Shield, a few different Kahr pistols, and the 3″ or 3.3″ barrel Springfield XDs will hold 6-7 rounds in single-stack versions, and the XD double-stack holds 9.

The more common 3.8-4″ service pistols blend concealability with 11 rounds in a flush-fit mag, and 15 or 16 in an extended configuration, which is easy on the grip but much less concealable. Glock 22s hold 15 rounds, while Glock 23s are 13.

Springfield XD and Kahr (bottom) 3″ barrels

Full-sized service pistols with 4-5″ barrels still only eke out 2d+1 until you hit the full 5″ barrel, such as in the Beretta M96.

For SMGs, there are of course the usual offerings from Heckler and Koch – the MP5 and UMP. Sig Sauer makes a cool-looking one with an 8″ barrel, which is pretty common for SMG-length weapons.

Finally, carbine-length weapons do exist, with barrel lengths that will tend to be in the 16″ range, but nearly anything in that regime will be identical for stats until one hits too-long barrels in which the bullet will have long-since past the point where the bullet is more slowed by friction than it is accelerated by expanding powder gas.

Sig Sauer SMG

Ultimately, the .40S&W is a nearly magical cartridge for pistols in GURPS. It hits all the breakpoints that GURPS has, allowing for good capacity, good damage, and excellent wounding.

The (0.5) armor divisor that standard rules gives really tamps this down from a “wears any armor and you’re very well proteeted” perspective. If you use the decimal multipliers, though, it occupies a nice space. 20% more injury, about equal penetration, but modern JHP ammunition expands to feasome diameters, easily meriting the pi++ designation given by my system.

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

7.62x35mm AAC Blackout


The 7.62x35mm AAC Blackout was developed to create a .30 caliber cartridge that could be fired reliably from rifles with a particular set of design constraints, mostly owing to the desire to use standard M4/M16 magazines and lower receivers, and to retain the 30-round capacity of standard magazines. Having a weapon that would autofire reliably (the 7.62x39mm does not in M16-shaped magazines) is generally a good thing, and having all that in combination with a more-lethal, more-quiet subsonic projectile was a design goal.

Given the popularity and number of variations that seem to be springing up for this near-wildcat, it would appear to have been somewhat successful. The original cartridge is supposed to have been designed around a military request for short-barreled rifles. The manufacturer took the design public. 

The odds of this replacing the 5.56x45mm as a primary cartridge are probably about zero. Even if the military moved away from the M855 family of rounds, I have to think they’d go for something closer to the 6.8x43mm rather than the .300 BLK. But that’s strictly opinion.


Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 406mm for the (test) barrel length. The difference in mission for the subsonic round means that it can’t really be used for checking consistency, but the lighter-weight bullets (at basically equivalent energy) can.

INPUT – Supersonic
.300 AAC Blackout
Chamber Pressure 53500 psi
Barrel bore 7.62 mm
Case Length 35 mm
Chamber Bore 9.2 mm
Barrel length 406 mm
Bullet Mass 125 grains
Aspect Ratio 3.7 L/Bore
Burn length 10.83 mm
Projectile Caliber 7.62 mm
Total Accelerated Mass 125 grains
Expansion Ratio 2 expansion
Projectile Load 1

The subsonic bullet is very different in both design and performance. It requires different inputs, being less than half the pressure of the supersonic round.

INPUT – Subsonic
.300 AAC Blackout
Chamber Pressure 21000 psi
Barrel bore 7.62 mm
Case Length 35 mm
Chamber Bore 9.2 mm
Barrel length 406 mm
Bullet Mass 220 grains
Aspect Ratio 5.1 L/Bore
Burn length 7.57 mm
Projectile Caliber 7.62 mm
Total Accelerated Mass 220 grains
Expansion Ratio 2 expansion
Projectile Load 1

Output Stats

Again, we’ll need two different charts for each weapon. The subsonic one is (to me) the more interesting, since it actually has a different job than the longer range rounds. I’ll give charts for both.

Supersonic 125gr projectile

The muzzle energy for this load with 406mm of barrel is 1,486 Joules

Subsonic 220gr projectile

The speed of sound is just over 340m/s (which is 1,115 fps). 

Notes
  • The velocity is at the muzzle. The velocity with both cartridges is tuned to the 16″ test barrel.
  • The 125gr bullet is just large enough to make a pi –> pi- transition not relevant. Instead, the real question, given the size of both projectiles, is if it gets a pi+ rating at very short range. Canonically, the answer to this is “no,” but at less than 100 yds from a reasonably-sized barrel, it might be quite nasty. If you like, and want to see players flock to this one, give it pi+ below the range listed, and pi otherwise.
  • No one is going to use this round in a barrel much more than 20″ long (maybe not even that), but the model is within about 60fps for a 78gr projectile from a 610mm barrel . . . so for what it’s worth, it’s accurate enough.
  • The point at which barrel friction slows the projectile more than powder gas pushes it is likely well before 607mm for the subsonic projectile. I suspect a 16″ barrel for 3d is about ideal.
  • Rumor has it that the .300 AAC Blackout at full power will still cycle from a 4.5″ barrel, which is why the table stops there.
Most of the alternate projectiles seem to have roughly the same energy and thus will do more or less the same damage from the test barrel. There’s enough mass in the bullet that getting a JSP to expand to a factor of 2 shouldn’t be a problem. While high-mass, short pistol cartridges tend to convert in the model using a rule that is mostly -1 penetration per die of damage, rifle-shaped fast-cartridges retain penetration better, and are closer to -1 per 2d. That would be about 5d-2.5, call it 5d-3, or 14.5pts. Calling it 4d pi+ is about right. 

The huge aspect ratio and high mass of the 220gr subsonic projectile makes my calculator want to give it 3d pi+ even for the regular FMJ round, and if it expands or tumbles, really wants to give it 2d+1 pi++ for a JHP. That might explain why one keeps hearing that for close-in work with suppressed rifles, certain groups of people who don’t exist definitely don’t want to use this cartridge. Which probably also doesn’t exist. 

In any case, if you’re feeling generous, 2d+1 pi++ for the subsonic JHP or JSP – still -1 per 2d, and bump it up one step from pi to pi+ is good for .300 AAC.

Platforms


There are basically two kinds of platforms for this chambering: AR15-style platforms, and bolt-action tactical or hunting rifles. There are many, many AR-15 style uppers that can be mated to any AR15, M16, or M4 lower – which is the part that the US Government considers the actual gun. 

The venerable and high-quality Remington 700 can be had in .300 AAC Blackout, and the AAC Model 7 can be tricked out with a suppressor. Given the heavy bullet and long 1/2D range, making a subsonic, suppressed bolt-action rifle for the precision delivery role might not be entirely insane. 

The last and most populous category will be a plethora of AR-15 (or M4/M16, as you prefer) lower receivers mounted with a suitable upper. Some of the suppressors that are built to go with this cartridge are very, very impressive, with the AAC SR-7 managing 39dB of noise reduction.

They don’t seem to come cheap. Most are $2,000 or $3,000 for a complete rifle, integrally suppressed or not, and most closer to $3,000 than not.

That being said, going straight to the source a 9″ barrel upper receiver ($1,000) plus the 39 dB suppressor (also about $1,000) will probably deliver 2d pi++ (220gr JHP) from the equivalent of a 16-17″ barrel length (9″ for rifle, 7-8″ suppressor) with impressive (lack of) acoustics.

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

5.7x28mm SS190 by FN

The 5.7x28mm SS190 cartridge was brought to market by FN-Herstal in 1993 (replacing the even lighter, plastic-core/penetrator tip SS90) in response to NATO’s search for a new kind of weapon for vehicle crews and behind-the-line combatants. It was designed to deal with the perception that body armor was going to be more prevalent on the modern battlefield (thus far, not terribly true), and that the somewhat ancient 9mm pistol did not have the killing power and effectiveness that was needed for such troops (that one’s certainly true).

FN really attacked the penetration angle, designing a (relatively) high velocity round that featured a steel penetrator tip.The SS190 will penetrate about 9″ into ballistic gelatin after punching through a Level II vest, which is roughly DR 10 in GURPS. If the 9mm pistol typically is on the order of 18″, that makes the overall penetration around DR 15 or so, giving an idea of it’s penetrative power after the AP is applied. 

Justifiably concerned about wounding power with such a lightweight round (roughly half the weight of the NATO standard 62-gr 5.56x45mm cartridge), the bullet was designed with a steel penetrator tip with an aluminum base. The construction (see pictures below) means that the bullet will break into two pieces (it more or less starts that way) after penetration. Arguments still abound over the wounding power of this round.

There are many loads for the pistol, but the standard one is the SS190 ball round, a 31gr bullet designed to hit 715m/s out of the P90’s 263mm barrel. The key loads are the SS190 (high velocity FMJ “AP” round), the SS195LF (commercial JHP), and the subsonic 56gr SB193. Other loads can be found as well.

Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 127mm for the (test) barrel length.

INPUT
5.7x28mm
Chamber Pressure 45000 psi
Barrel bore 5.7 mm
Case Length 28 mm
Chamber Bore 6.2 mm
Barrel length 263 mm
Bullet Mass 31 grains
Aspect Ratio 2.25 L/Bore
Burn length 4.2 mm
Projectile Caliber 5.7 mm
Total Accelerated Mass 31 grains
Expansion Ratio 1.6 expansion

Output Stats

The one thing you have to know about the various PDW cartridges is that the stats that will come out of my ballistics calculator are almost certain not to match up with High-Tech. The basis for calculation was slightly different.

That being said, one can see that the 5.7x28mm cartridge is definitely pistol-class, even out of long barrels. The bullet well and truly earns a pi- rating, and even a bullet that tumbles and fragments will probably only barely earn a pi rating if the GM is feeling generous. From that perspective, unless the GM is using some sort of calculator or feeling generous, the lower pi- rating of all of the bullets will mitigate towards the highest energy round possible unless the goal is to push it through a suppressor, in which case the heavier, slower, lower energy SB193 will be called for, giving up some penetration in exchange for (relative) silence.

So, here’s the chart:

Notes
  • The velocity is at the muzzle. The velocity with a P90 263mm test barrel is tuned to match real-world data at 715m/s. Out of the 122mm Five-seven pistol, it develops just shy of 600m/s according to my model. 
  • The pi- to pi range is a bit dubious in this case. The bullet’s construction means that fragmentation is all but inevitable, but the low mass of the SS190 round, combined with the low cross section, means that pi- is likely the better figure regardless of range.
The P90 uses a 163mm barrel, which puts the KE-based damage for the cartridge at about 3d-1 using this model (compare with 2d+2 in High-Tech). The trick here is that the High-Tech stats give the basic round the full armor divisor of (2), the only resolution that GURPS can provide. With a more-realistic divisor of 1.25 to 1.5, and looking at the “penetrates about DR 15 ish” above, we can see that a net damage rating of 3d-1 (1.5) pi- would penetrate to about DR 15, but only do about 4-5 points of wounding per shot. This is roughly consistent with the observed performance of the round, though 3d-1 (1.5) pi or 2d+2 (1.5) pi would not be tragic, either, retaining the DR 13-15 penetration observed in body armor testing, but wounding like a 9mm pistol. 

One last thing: I’m dubious about the penetration statistics, though it is hard to argue with data. DR 15 is quite nearly the penetration of a M4 carbine, a cartridge with over 3x the energy and similar cross section. 

The two barrel lengths of import for most uses are the 263mm barrel of the P90, and the 122mm barrel of the Five-seven pistol.

Alternate Loads

As noted earlier, the JHP load likely won’t expand sufficently to mathematically eke out a boost in damage, but for GURPS purposes, a good rule of thumb here will be to subtract two points of penetration (so the pistol becomes 2d (1.5) pi and the PDW is about 2d+1 (1.5) pi ). 

The other important load is the 56gr and 305m/s SB193, designed for subsonic use with suppressors. That is 1d+2 pi-, with no armor divisor. Aim for the head, and fire a lot of bullets.

Platforms


There are basically three classes of platforms – or rather, two concrete weapons, and then another class of “if you want this cartridge, you can . . . “

The Five-seveN pistol is the companion piece to the PDW that formed the basis of the cartridge. It has low recoil, a 20-round capacity, and the long overall length relative to the 9mm and other handgun cartridges means that one needs monster hands to completely enclose the grip. The relatively low damage of the round means that it’s wise to fire more than once, but then, if something’s worth shooting, it’s worth shooting twice. Or more. If you can handle the grip, I suspect that putting bullets through more or less the same hole is the rule of the day.

The design platform for the weapon is the P90 PDW, a compact weapon with an unusual layout and even more unusual magazines. They top-load, and eject through the stock. The overall length and compactness of the weapon make it very handy for entry and close-quarters work. Despite the claims of 200m effective range of the platform, I suspect that nearly all of the work done with this weapon (and it’s found its way into service with numerous SWAT-style teams internationally) is at 50m or less, where penetration is maximized, the odds of getting multiple rounds on target are very high, and the teams can rely on multiple hits and compound wounding tracks to incapacitate.

Both the pistol and PDW can be found in High-Tech.

The final class of platforms are weapons like the AR-57, which is basically a 5.7x28mm upper receiver, complete with top-loading magazines, mounted on an AR15 lower. The magazine in the photograph to the right does not feed rounds, it catches them – it’s hollowed out with the spring and follower removed. Personally, I’d probably try and line such a device with felt or something, so as to minimize the rattle, but one can also just remove the ersatz brass-catcher and let the rounds eject through the mag well. The barrel of this weapon is 16″, perhaps even squeezing out 3d+1 raw damage, but certainly earning 3d. Such uppers seem to retail currently for $700-750.

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

9x19mm Parabellum

The 9x19mm was invented by Luger in 1902. It is perhaps the most widely used pistol cartridge worldwide, and with recent advances in hollow-point ammunition reliability, is poised to reclaim its former spot as the issue cartridge of the FBI over the .40S&W.

There are many loads for the pistol, but the most common seem to be the 115gr, 124gr, and 147gr loads. They are usually available in full metal jacket (FMJ) and various flavors of hollow point. From a GURPS perspective, the most important load is probably the 124gr NATO standard round – an 8 gram bullet fired at 1250 fps from a 5″ barrel – it’s the standard for 2d+2 as well as pi pistol rounds. A reference bullet, so to speak, defined as doing both 9 points of penetration and 9 points of injury.

So we’ll work that one up, and then talk about variations.

Ballistic’s Calculator Inputs

Basic inputs for the calculator are as follows, selecting 127mm for the (test) barrel length.

INPUT
  124gr 9x19mm  
Chamber Pressure 32900 psi
Barrel bore 9 mm
Case Length 19 mm
Chamber Bore 9 mm
Barrel length 127 mm
Bullet Mass 124 grains
Aspect Ratio 1.85 L/Bore
Burn length 8 mm
Projectile Caliber 9 mm
Total Accelerated Mass 124 grains
Expansion Ratio 1.66 expansion
Projectile Load 1
Output Stats

The pistol cartridge is relatively high power as far as pistols are concerned – much more so than the .45 ACP that it was supposed to replace (and from a service perspective, largely did replace). It develops a considerable velocity in a short barrel, and the lowest penetration predicted by the model is on the order of 2d out of just over a 1.5″ barrel – not that anyone uses one that short. Even derringers come with a 2.5″ barrel, mostly!
So, here’s the chart:

Notes
  • The velocity is at the muzzle. The velocity with a 5″ test barrel is tuned to match real-world data at 1250fps, for NATO standard ammo. This is not the highest energy 9mm available, but it is the standard GURPS 2d+2 pi bullet, so it’s what I chose. 
  • 1250 fps is pretty good for a 9mm load, though – not that you can’t get more, but in self-defense loads (JHP), the fastest 124gr tested at this site was slower than the standard FMJ NATO load.
  • There is no pi to pi- range; this bullet does not gain appreciable wounding by tumbling.
Some more notes on barrel length. You can see that it will penetrate as well as a .45 ACP with derringer-length barrels. At the more standard 2.5″ or higher, it’s at least 2d+1, and in the “service pistol” barrel length from 4″ to 5″, it’s all 2d+2.

Now, for SMGs you can get longer barrels – but not as long as you might think. The MP5K has only a 4.5″ barrel (2d+2) but can hold a lot of bullets and fires them quickly. The more robust MP5 is 225mm for the longest barrel, which only ekes out 3d-1. To get to the full 3d you’ll need/want a 9.5″ barrel, but you can’t get to 3d+1 until you’re over 450mm. Even the Beretta Cx4 Storm is only 422mm – most carbines seem to like to come in 16″ barrels or smaller (3d), but the Citadel M1 does come with an 18″ barrel that should deliver about 3d+1. Of course, if you are toting a 35″ weapon around, you can do a lot better than that for damage, ammo weight, etc with a 5.56x45mm carbine or even a full-size rifle in a bullpup. The reason you do this (carbine in 9mm) is for Accuracy, not damage.

Alternate Loads


As noted earlier, the more common loads than the military one will be hollow points. That being said, there are slightly hotter 124gr FMJ loads, the hottest I could find only being 1310fps, which my model gives as being achieved at about 36,200psi input. That gives 9.8 points of damage, which is enough to eke out 3d-1 pi.

Alternate loads tend to be alternate weights, with a lot of 115gr stuff being available as very high velocity rounds, especially from SMGs, and 147gr heavy bullets from pistols, both of which are available in JHP. The heavier bullets will tend subsonic, which makes them excellent for platforms like the MP5SD6 – an integrally suppressed weapon.

Some of the best JHP will expand to as much as 0.6 to 0.7″ in diameter, which is roughly double what the starting diameter is. That’s very good, and more typical of JSP rifle rounds – which have a lot more body to work with.

That means a proper JHP round really earns it’s pi+ rating. The GURPS rules give JHP ammo a (0.5) armor divisor. The more accurate way to do it is to subtract 1 point of penetration per die. Lo and behold, this makes the best 9mm hollow point from the prior web page (1170fps and 0.66″ expansion, the Golden Saber +P loads) provide 2d pi+, which is the same penetration and injury as a .45 ACP, but with a heck of a lot more shots per magazine and less recoil. 

Platforms

There are almost too many to count. I’ll ping in a few important ones.

Pocket pistols with a 2.5″ barrel that would include derringers and small concelable pistols like the Kahr and other 9mm models. These will often hold fewer than 10 rounds.

Concealed carry pistols with a 3-3.5″ barrel that are “commander-sized,” which means small and easy to carry, but likely double-stack weapons that will hold over a dozen shots, perhaps closer to 15.

Full-sized service pistols with 4-5″ barrels. These will hold 15-18 shots in the magazine.

SMGs and Carbines with 9″ to as high as 16″ barrels. Nearly all will do about 3d-1 or 3d pi damage, and with the right hollow-point round will deliver 2d+2 pi+, which is a good reason to carry one (still not as good a reason as to carry a carbine with an assault rifle chambering for many reasons).

As noted above, subsonic 9mm is good for suppressed weapons, the most famous of which is probably the MP5SD series.

The Reloading Press is an at-least-weekly feature here on Gaming Ballistic for 2016. Each week it looks at some interesting real-world cartridges and presents them with hopefully-useful information in GURPS Format.

6.8x43mm SPC

The 6.8x43mm SPC cartridge was introduced as an attempt to increase the lethality of the M16 and (especially) M4 pattern rifles. The cartridge is more-or-less designed to fit into the same magazine length as the 5.56x45mm NATO standard bullet (but it’s not true that they use the same magazines – they don’t), and the lower receiver of the AR15/M4/M16 platform can be used unmodified with the new cartridge. The bolt, chamber, and barrel of course must change, and that can be done with an upper receiver swapout.

Whether or not this was the true design goal, one outcome of the design process that led to the 6.8x43mm is that the test velocity of the barrel is achieved with a 16″ barrel, rather than the 20″ standard for the 5.56x45mm. That means that the M4, with its 14.5″ standard barrel, is much closer in barrel length to the optimal barrel the cartridge is designed around.

Ballistic’s Calculator Inputs


Basic inputs for the calculator are as follows, selecting 406mm for the (test) barrel length.

INPUT
6.8x43mm SPC
Chamber Pressure 54000 psi
Barrel bore 6.8 mm
Case Length 43 mm
Chamber Bore 10.7 mm
Barrel length 406 mm
Bullet Mass 115 grains
Aspect Ratio 3.6 L/Bore
Burn length 21.3 mm
Projectile Caliber 6.8 mm
Total Accelerated Mass 115 grains
Expansion Ratio 2 expansion
Projectile Load 1

Output Stats

The rifle develops appreciable damage at near pistol-length barrels, at least within the assumptions of the calculator. It would equal the injury of a .45 ACP even at pi- ratings in a barrel the size of a long revolver. Even so, calling it “pi-” does it little justice. It would earn a wound channel modifier of 0.7 if the scale were left open to any number, compared to the 0.5 of the 5.56x45mm, the 1.0 of a 9mm, and a 1.2 of a 0.40 S&W.
So, here’s the chart:
Notes
  • The velocity is at the muzzle. The velocity with a 16″ test barrel is tuned to match real-world data at 2575 fps, the highest energy load listed on the Wiki page. I do this because GURPS damage is based on kinetic energy, so no GURPS PC worth their salt will choose anything less than the highest energy if pure penetration/lethality is at issue. If you’re doing supppressed subsonic shooting, that changes.
  • The pi to pi- range is where the damage drops from piercing to small piercing. For very short barrels (smaller than 177mm in my model), the bullet is slow enough that it will not yaw and fragment, and so it’s only good for pi- rather than pi. This is defined as 600m/s in my model, which is somewhat arbitrary.
  • It’s possible that the damage (penetration, really) is perhaps 10% high. That would still give a 20″ barrel about 6d-1, and a 14.5″ barrel 18 points of penetration, or a full 5d out of an M4 platform.
At any useful barrel length for a rifle cartridge, that is, about 9″ and higher (and that’s a darn short rifle), there is some appreciable range at which it will do its full pi damage type. It is an intermediate between the 5.56 and 7.62 NATO offererings in almost every way:
  • Half the diameter of the two rounds would be 6.59mm
  • Half the bullet weight between the 62gr and 168gr standard marksman’s bullets for each platform is 115grains, which is where the standard bullet comes in
  • The standard AR-15 length magazine holds 25 rounds of 6.8mm SPC; the AR platform magazines typically hold 30, while the 7.62×51 hold 20.
  • The 7.62 is about 3400 Joules, the 5.56 about 1760J. Average that to get about 2,550J, where the actual round comes in at about 2,300J.
For GURPS gunners, it’s a very good cartridge. 6d out of a 16.5″ barrel makes for a one-shot death check against Joe Average, bringing him from 10 HP to -11 HP in one torso hit. Against the vitals, 21 turns into 63, enough for a one-shot instant auto-kill. Highly efficient. The Rcl for these weapons is typically 2, so it’s no worse than the M4 or M16 it replaces, and better than the full-size battle rifles. The 1/2D range of 530yds is 30% higher than the 5.56x45mm.
Regardless of the real-world, it’s a fine, fine cartridge in GURPS.
Not everyone feels the same way about the cartridge in the real world as it stacks up vs. the modern versions of the 5.56x45mm, the Mk262 77gr long-range cartridge. A data-intensive comparison can be found here.
Platforms

You need a purpose-built upper receiver (or at least a barrel, chamber, and bolt change) to shoot this cartridge. Some rifles and uppers can be found below.

  • The Barrett REC7 is the only 6.8 SPC rifle statted up for GURPS, found (of course) in GURPS Tactical Shooting. For a list price of $2,800, one can be yours.
  • I would love to get my hands on a Desert Tech MDR in 6.8 SPC, but they’re not out yet. They’re also supposed to cost between $2,000 and $3,000. But it’s a bullpup, so mrowr.
  • Stag arms makes a piston-driven platform in 6.8x43SPC that’ll run the buyer about $1,100, but you need to have a lower receiver to put it on (about $300, and that’s the part that counts as a “firearm.”
  • LWRCI went the entire nine yards, redesigning the magazine well and contractiing with Magpul to make the only polymer-case magazines for this cartridge. The rifle itself is about $2,200 complete, and each magazine costs a darn-reasonable $25.
  • The magazines for these rifles are quite finicky in my experience. Of the four 25-round steel magazines I own, two will not feed reliably. Barrett and Magpul make good ones, for $50 and $25, respectively.
  • You can find some of the above, and many others, in this article. They’re all probably very expensive, though – this round never caught on as much as marketing hoped it would!

The Reloading Press is going to be a new short feature for me in 2016, based on a few comments from friends of mine in other media.

Each post will contain a cartridge and stats for GURPS – sort of. The way I’ll be doing this is to use my ballistics calculator, which will give gameable and consistent stats.

In many cases, there won’t be much difference between various versions of a bullet or cartridge. As an example, at some point I’ll compare 115gr ,124gr, and 147gr 9mm ammunition. That will, within GURPS’ resolution, likely not amount to much.

5.56x45mm Mk318 mod 0

This cartridge is the USMCs answer to the fact that the 62gr M855 (about 4 grams, and 940m/s out of a 20″ barrel) didn’t pereform that well when fired out of the usual short-barreled M4 carbine, which has a 14.5″ (370mm) barrel standard.

The ammo is built to a 2 MoA standard, which means that the maximum accuracy a weapon can get using this ammo is Acc 5 (about 1.8 MoA, close enough).

Pertinent stats for the ballistic calculator:
Continue reading “Reloading Press: 5.56x45mm Mk318 mod 0”