However, other guns are not. What’s been discovered over the years is that a number of different chamberings can actually headspace another cartridge, sometimes with a little force…but usually with results ranging from innocuous to disastrous.
Typically it starts with someone who heard that you could shoot X through a gun made for Y. Again, in some cases – such as .38/.357 – it’s true, but in others it’s just not.
But what can happen if you do?
The best-case scenario is that the shooter has errantly chambered a round that can safely headspace in the gun, but the projectile is smaller than the bore diameter. For instance, if someone has – in error – placed a .243 cartridge into a .308 rifle.
In this case, the projectile will leave the barrel at a very slow velocity as most of the gas has already gone out of the barrel. Accuracy will be almost nonexistent and that’s pretty much it.
The worst case scenario is if the projectile is larger than the bore or if the cartridge doesn’t completely headspace but the action closes anyway.
In this instance, a catastrophic malfunction will result. The bullet can completely split the barrel if you’re lucky in the first case, but otherwise this will result in rupturing the chamber. In other words, kaboom.
So…with that in mind…how can you use multi-caliber firearms safely?
First, by knowing what guns or calibers truly do allow for safe use of different calibers, and they are few, and exactly how that works. In other words, the way things are.
Second is by understanding how and why that’s possible in those instances, so you understand why things are the way they are.
Thirdly by not taking chances based on what people tell you. If you hear something from someone, look it up. If you don’t find information confirming it, don’t do what they’re suggesting.
So, what are some common examples? Here are a few common ones. There may be some uncommon ones, but we can leave them for another time.