Reloading Press: 9x19mm (9mm Parabellum)
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 |
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!
- 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.
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.
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.
I got a comment from Hans-Christian Vortisch, but Blogger was struggling with his OpenID. So here we go:
Hans says: "Weird barrel selection in the chart, both in metric and inch 😀 "
Yes, the way I pick my barrel lengths is to first put in the information for the most "standard" load using the test barrel length and searching for target velocity. Then I use Excel's Goal Seek function to find breakpoints for GURPS damages. Each barrel length is what is required to provide exactly that damage rating. So for the 9mm, the base penetration is 9 points (2d+2). So for the next smaller barrel length, I solve for 8 points (2d+1) and then 7 points (2d). Since a quick search shows that barrels don't get much smaller than 1.8" (most "short" barrels were 2.5" in 9mm, even in derringers), that's as far as I went. We're starting to get to the point where the results'd be weird anyway, though, since the powder is probably not completely consumed, where the model assumes it is within a few mm of the end of the case (that's the "burn length" parameter).
For longer barrels, I go up point by point until the barrel goes beyond anything reasonable. Again for 9mm, in order to hit 3d+2, you need a .50BMG-sized barrel, and that's not even including the fact that at some point, likely far before the 3d+2 point is reached, the drag on the bullet within the barrel will decelerate it more than the pressure from the much-higher volume of powder gas will push it. So I suspect you will simply never get that much penetration out of a 9mm, but my model is what it is, and needs a human to interpret it.
Hans says: "Note that subsonic loads are discouraged for the MP5SD series, since the perforated barrel of the MP5SD is designed to bring down the MV of
standard ammunition to subsonic levels. If you use subsonic ammunition,
the MV goes down so far that the weapon is no longer very useful (check
the stats, especially the Dmg of the MP5SD3 in HIGH-TECH, p. 123). It's
unnecessary double-dipping. Most subsonic loads in the MP5SD also reduce
reliability. However, also note that not all 9.5-g (147-gr) loads are
subsonic, those that aren't can be used efficiently in the gun. "
That's a good point – I wonder if that's unique to the MP5, or if most integrally-suppressed 9mm SMGs are that way?
How much of a difference is it using 'cheap' 9mm ammo? I'm thinking of like the 115grain 'Tul-ammo' or similar (often Russian-made) that you'd get at Walmart, the cheapest 9mm FMJ you can find.
How about the cheaper JHP rounds (the quality level below the pricey 'Self Defense' brand-name applications)?
In GURPS terms, is there significant change in stats? I looked at the shiny table with the JHP comparisons (Golden Saber +P at the top of the chart) but I'm not quick enough yet to translate it to Gun-Stat language, much less figure out where a cheap round would show up on that chart.
My guess is that you've covered this somewhere already – if so, point me in the right direction and I'll look it up!
The stats are probably the same from a velocity and damage perspective. Differences in damage due to variable velocity from crappy powder or poor quality control on how much powder are going to be sub-resolution.
the place where I'd hit users of "cheap" ammo is in reliability. Increased chance of a jam or stovepipe requiring a Ready maneuver to clear it, and if you don't make a point of cleaning the weapon, Malf would increase further.
very nice, that sounds like it would replicate real world pretty well – you see a lot of complaints of shell jams/fail-to-feed when it comes to the cheap stuff, as well as the 'dirtying' effect.