Prepper's Armory: Ammo Mishaps, part 2

In my previous post on this topic, I discussed what can happen to guns when the wrong ammunition, or ammunition loaded to excessive pressure, is fired in them. In this installment, I'll look at ammunition which, while having similar external dimensions, are actually two distinct cartridges.

One that’s not heard about as much today is the .38 ACP chambered in early Colt semi-automatic pistols. The original loading of .38 ACP had very similar ballistics to .38 Super, enough to damage the firearms of the time, and so the cartridge was reduced in power. However, the later-designed .38 Super has nearly identical case dimensions and can be chambered in those older guns. Modern .38 Super fired in antique .38 ACP pistols can damage the gun and possibly even injure the shooter.

Similarly, the older 7.63 Mauser and more recent 7.62 Tokarev are nearly interchangeable as to external dimensions, but their current loadings are not comparable in power. I had the misfortune of being shown a pre-World War I C-96 Broomhandle Mauser that had been fed a regular diet of 7.62 Tokarev rounds. The shooter hadn't been injured, but the gun was ruined.

Data from Hornady Handbook of Cartridge Reloading

Another common issue of concern is military surplus rifles being rechambered in cartridges well beyond their pressure limits. Years ago, Bloke on the Range participated in a video about a Short Magazine Lee Enfield rifle rechambered for 7mm Remington Magnum. 

Understand that .303 British, the original chambering for the SMLE, has a maximum pressure of 49,000 psi according to the Sporting Arms and Ammunition Manufacturers Institute (SAAMI) standards. British and Commonwealth arsenals use intentionally overloaded ammunition called proof cartridges to certify firearm safety. These generally develop around 10% over maximum pressure of a standard round, or approximately 54,000 psi in the case of .303 British. In comparison, the 7mm Remington Magnum has a 61,000 psi maximum. That’s a 12,000 psi increase over a standard pressure cartridge! By the end of the video, the rifle was not in good shape.

Data from Lyman Reloading Handbook

There are also military rifles that were rechambered during their service lives due to a change in the issue cartridge. For example, right around the turn of the last century, the German military changed their standard cartridge from the Patrone 88 to the S Patrone. The cases were nearly identical, but the bullets differed in shape, weight, and most importantly, diameter.

The Patrone 88 fired a .318 inch bullet at around 2,100 FPS. The later S Patrone was a .323 inch bullet that traveled at nearly 2,900 FPS. Now, .005 inches may not sound like a lot, but we are talking about a significant pressure increase in rifles over a century old at this point, the earliest of which were originally designed for black powder.

Data from Lyman Reloading Handbook

In fact, unless the owner really knows what they're doing, some of these early rifles probably shouldn’t be fired at all. The new (or rechambered) barrel should have the current chambering stamped into it, but this isn't always done. If the chambering of a rifle is in question, a chamber casting can be made for proper measurements.

There are other examples, but I hope by this point the message is clear: know the firearm and its appropriate ammunition. As mentioned previously, a good resource is SAAMI, the Sporting Arms and Ammunition Manufacturers Institute.

Be careful, be safe, and enjoy many more years of shooting without blowing up any guns.