"Yeah, I don't carry a [gun of X type] that isn't in [a specific caliber, a caliber above X arbitrary value, etc]."
And, if you haven't yet, you will.
What is it about specific calibers, be it .308 or .45 or something else, that really turns people on? After all, it's just a measurement of one particular area on the projectile. A fetish for bullet mass, or better yet cartridge muzzle energy, would make more sense. Yet, there it is.
Today I want to address two specific hymns sung by acolytes of the Cult of Caliber, the first being this:
"If a 5.56 round fails to [tumble/fragment/expand], then what you really have is just a glorified .22."
Variations on this theme appear everywhere, even some well respected defense journals. But something has been bugging me about it.
The first is, isn't this basically the same as saying "if a 5.56 round hits a target and performs exactly like a .22 LR, then it won't be any more effective than a .22 LR"? It may be true, but besides being a bit disingenuous by singling out 5.56, it doesn't really seem useful, as it doesn't tell us anything about how likely it is that 5.56 will perform like a .22.
My other objection is that there's nothing special about a caliber. It's just a measurement, either the diameter from one land to another, the diameter of the grooves, the diameter of the projectile itself, or even just some arbitrary number that's kinda close to one of those measurements. There aren't any caliber-specific performance nodes where one caliber has something special going for it over another.* The statement above frames the situation as if 5.56 has some special quality, that other calibers don't have, which is detrimental to its terminal effectiveness. Even assuming the above statement were true, why would 5.56 be special? Shouldn't the below statement be just as true?
"If a 7.62 round fails to tumble, fragment, or expand, then what you really have is just a glorified .32 ACP."
.32 ACP from a handgun produces about as much energy as .22 LR from a rifle. It's almost certainly not any more effective. How then, even if the oft-heard statement about 5.56 were true, would it inform us about any deficiency in the cartridge? And if it's not true, why take it seriously?
A similar, but different quip is also often heard, relating to 5.56's parental history:
"5.56 is based on the .222 Remington, which was intended as a varmint cartridge."
While it's true that the .222 Remington was and is popular with varmint hunters, the 5.56 was, with some very explicit supporting evidence, designed specifically as a battle cartridge. Indeed, one could as easily say that the 7.62 is just an overgrown varmint cartridge, it being the same caliber as the .32-20, which was a common caliber for small game in previous years. This quip is a bit more banal, and really isn't based on anything but semantics. A chambering isn't good for only one thing; just because the .222 Remington sees a lot of use as a (long range) varmint cartridge doesn't mean that you couldn't easily kill a person with it, or that it's only effective against varmints. Considering the fact that varmints are usually dispatched by blowing gigantic holes in them, a "varmint" cartridge loaded with appropriate bullets might be a real man-stopper.
It's simply not appropriate to judge a cartridge by its caliber alone. Caliber is just a measurement; high velocity bullets are not like icepicks; they do not simply poke a hole of their size and shape, even if they don't do anything exotic. For example, here's a video of a perfectly stable .30 Carbine bullet impacting a block of gelatin and doing some pretty dramatic things to it. This post isn't intended to settle whether 5.56 is a good man-stopper or not once and for all (I was hoping its steady half century of use for that purpose would), but I am hoping I've thoroughly put down those two particular arguments.
*This isn't entirely true, as propensity for yaw actually scales with caliber. Here's a paper describing the phenomenon. However, this assumes homologous bullets, and so you could have a .30 caliber bullet that yaws as easily as a .22 caliber bullet, etc., if they weren't homologous.