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.
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.
- 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 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.
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.