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How Effective are Pistol Caliber Carbines?

This is a guest post by Andrew Betts

pistol caliber carbines
Pistol Caliber Carbine Effectiveness

Does size really matter? Is longer better? No, not that. Get your mind out of the gutter and read the title again. We’re still talking about guns, here.

In a recent article, we detailed some of the advantages to using a pistol caliber carbine in the same caliber as your carry pistol for home defense. In this article, we’d like to take a detailed look at what effect a longer barrel has on terminal performance.  Does the longer barrel really make the cartridge more powerful, or is a pistol caliber carbine little more than a handgun with a stock when it comes to its potential to cause tissue disruption?

To be sure, the longer sight radius, optic mounting options, and the presence of a stock still offer substantial advantages over a pistol and the low recoil of a pistol caliber carbine still makes it really easy to shoot well, no matter what the terminal performance is.

Does that longer barrel really mean higher velocity, though?  If it does produce higher velocity, is that necessarily a good thing?

Now, it might seem obvious that the longer barrel would always produce substantially higher velocity. But that’s not necessarily the case. In fact, some pistol calibers such as .45 ACP can actually show little or no substantive velocity gain going from a four or five inch service pistol to a sixteen inch carbine. The reason is that the powder can be completely consumed and pressure begin to drop to the point that friction starts to overcome pressure as the dominant force in the barrel.

If you want to get all super geeky about it, www.ballisticsbytheinch.com has tables that list measured velocities for various barrel lengths and they include several different loads for each cartridge. They list that breakeven point for .45 ACP at around the 11”-12” mark, depending on the load tested. Other cartridges can pick up substantial velocity from the longer barrel, though. When I tested a hand loaded .40 S&W 180 gr Speer Gold Dot from a Kel-Tec Sub-2000 carbine, I got a 240 fps increase in velocity, but I used a slower burning powder. A more typical increase in velocity for factory ammo in this caliber would be about 150 fps, or so.

Nevertheless, it demonstrates that notable velocity gains can be made and it gives an example of what the best case scenario is for a typical auto pistol cartridge in a carbine. Those gains don’t necessarily result in any notable difference in tissue damage, though. The bullet fired from the pistol resulted in an average expanded diameter of 0.617” while the one fired from the carbine had an average diameter of 0.660”. The pistol bullet penetrated 14.5” and the carbine bullet penetrated 16.6”. The wound tracks looked very similar

While there are some moderate velocity gains when you fire an auto pistol cartridge from a longer barrel, there doesn’t appear to be a substantial difference in down range effect. But there’s a big difference between typical auto pistol cartridges and magnum revolver cartridges. What happens when you fire .357 mag ammunition from a lever action?

The results might surprise you. To begin with, the velocity gains from a longer barrel are substantial for .357 mag as you might expect. It’s the terminal effects that may surprise you. Underwood 158 gr XTP clocked in at just under 1,500 fps from a 4” Ruger GP-100, which is already pretty respectable, but it reached nearly 2,000 fps when fired from the 18.5” barrel Marlin 1894C. That’s pure, uncut, primo impressive.

Unfortunately, that extra velocity caused the bullet to expand very quickly and to shed some weight and it only penetrated to 10.3”, falling well short of the 12” minimum, making it unsuitable for defensive use. The extra velocity actually hurt performance. This is a concept that is new to some people. At first glance you can’t be faulted for thinking that, since velocity is good, more velocity is better. Bullets that are designed to expand only perform correctly within a specific velocity window, though.

On the other hand, this American Eagle 158 gr jacketed soft point performed perfectly in the rifle. It penetrated to 15.1” and expanded to an average diameter of 0.783”. With an impact velocity of 1,840 fps, it produced a massive stretch cavity and at that speed, it is likely that the stretch cavity would have created some tearing, which can increase the size of the permanent cavity. In short, the performance of this budget oriented load was absolutely phenomenal.

Unfortunately, when this load is fired from a revolver, it doesn’t generate enough velocity to expand much and simply punches a clean, small hole through about 22” of tissue. So it works very well from a carbine, but it doesn’t perform so well from a revolver. In my testing I ran into several instances like that at different bullet weights and with different projectile designs. A load would perform very well from a revolver, but expand too much and penetrate too shallowly from the rifle. Or the bullet would perform very well from the rifle but fail to expand if the same load was fired from the revolver.

To keep things in perspective, any hole in a bad guy is better than no holes in a bad guy. Still, it seemed like you just couldn’t have a load that would produce good terminal effect when fired from both the revolver and the carbine. If you think about it, that’s a pretty monumental task that we’re asking it to do. The rifle barrel can add 400-500 feet per second to the velocity and we want the bullet to still expand and penetrate no more than 18” but greater than 12” (for personal defense).

I was starting to believe that I might not find a .357 mag load that would perform well from both a handgun and a rifle. Then I tested Remington’s 180 gr semi-jacketed hollow point. This fantastic cartridge seems to defy physics. While the penetration was a little on the deep side, the projectile did expand when fired from both the rifle and the handgun. Velocity was respectable for both. In fact, the velocity still would have been respectable if they were 158 gr bullets. At 180 grains, the velocity isn’t respectable, it’s astounding.

Another interesting result was when I fired Winchester .38 special 130 gr PDX-1 from a carbine. I did this almost as an afterthought during the test. I didn’t expect much velocity gain but was surprised to find that, while the 4” S&W Model 13 only yielded 940 fps from this load, the 16” Rossi M92 yielded almost 1,200 fps. That little pill held up pretty well, too, with near perfect weight retention and 17.4” of penetration. It might not be your first choice for a carbine load but the recoil basically never happened and the noise was substantially less than almost any other center fire combination. This might actually be a good choice for recoil sensitive people.

There are obviously a lot more loads out there that are not covered in this article. As always, it’s up to you to test the ammunition you intend to use in your own firearm.

My recommendation, if I might be so bold as to make one, is that if you intend to pair a pistol with a pistol caliber carbine, that you identify the best load for each and keep them loaded with that ammunition and perhaps identify a third type that works fairly well in both. For example, I would load my S&W Model 13 revolver with the 158 gr Gold Dot and load the carbine with the 158 gr JSP. I would also keep Remington 180 gr SJHP as spare ammunition for both. This article isn’t intended to dissuade you from using pistol caliber carbines for defense. Like many things in the firearm world, though, when we start looking deeply into the matter we find that there is no simple solution.

Andrew Betts served with the Arizona National Guard for over 12 years, including a tour to Afghanistan.  Visit his YouTube Channel for more great shooting information.

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