Reprise: It’s Not the Length of Your Barrel, It’s How You Use It

My friends over at the Liberal Gun Club asked if they could have my BBTI blog entries cross-posted on their site. This is another in an occasional series of revisiting some of my old articles which had been published elsewhere over the years, perhaps lightly edited or updated with my current thoughts on the topic discussed. This is an article I wrote for Guns.com, and it originally ran 3/7/2011. Some additional observations at the end.

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“What is the best barrel length?”

It’s a question I get a lot, thanks to my involvement in Ballistics By The Inch. And invariably, I say in response: “it depends.” As in, it depends on what you’re going to use it for.

OK, first thing: I’m talking about pistol cartridges, not rifle cartridges. Got that? Pistol cartridges.

That’s what we studied with our BBTI project (actually, continue to study, since we’ve done several expansions of the cartridges and ammunition tested already, and have another big expansion coming up the beginning of May.) Now that we’ve cleared that up . . .

Different barrel lengths are good for different purposes. The longer the barrel, the longer the sight radius, and so the easier it is to be accurate with the gun. The shorter the barrel, the easier it is to conceal.

And barrel length has an effect on the velocity of a bullet (and hence the power of that bullet.) How much of an effect? Well, it depends.

No, seriously, it depends. Do not believe it when someone tells you “oh, the rule of thumb is about 75 (or 25 or 100 or any other number) feet per second for each inch of barrel.” That number may be right for one given ammunition in one given gun for one given inch of barrel length – but it will not hold true as a general case. Don’t just take my word on this – look at the actual numbers from tests we conducted, using almost 10,000 rounds of ammunition. You can go to the BBTI site and see the data for yourself (it’s all free, with no advertising or anything), but here are two examples:

Cor Bon 165gr JHP +P .45 ACP ammo was tested at 1001 fps with a 2″ barrel. That jumps to 1050 fps with a 3″ barrel, or an increase of about 50 fps. Going to a 4″ barrel you get 1163 fps, or an increase of 113 fps. But when you go from an 10″ barrel to a 11″ barrel, you only get an increase of 23 fps.

Let’s look at Federal Hydra-Shok 230gr JHP .45 ACP. It starts at 754 fps with a 2″ barrel, and jumps to 787 fps out of a 3″ barrel – an increase of 33 fps.  Go to the 4″ barrel and it tested at 865 fps – an increase of 78 fps. And when you go from an 10″ barrel to a 11″ barrel, you only get an increase of 4 fps.

Do you see my point? It not only varies by ammunition, it also varies by which inch of the barrel you are talking about – the inch between 3 and 4 sees a lot more increase than the inch between 10 and 11.

Almost all handgun cartridges show this effect, and it makes sense: pistol cartridges use a fast burning powder, but it still needs a little bit of time to completely combust. The highest acceleration comes at first, and then usually handgun bullets plateau out somewhere between 6″ and 10″, with little additional velocity with longer barrels past that point. The graph of our first example shows this very well:

Some cartridges even show velocity starting to drop off with longer barrels, as the friction of the bullet passing through the barrel overcomes any additional boost from the gunpowder. Notably, the “magnum” cartridges (.327, .357, .41, and .44) all show a continued climb in velocity/power all the way out to 18″ of barrel length (the maximum we test), though the amount of increase tends to get smaller and smaller the longer the barrel.

So, back to “it depends”: if you want a lever-gun or carbine, which uses a pistol cartridge, you’re best off using one of the magnums if you want maximum power. If, however, you want to use a carbine for an additional power boost and better aiming, one with a barrel length somewhere in the “plateau” for a given cartridge makes sense (and this is why subguns typically have barrels in the 8 – 10″ range).

For a hunting pistol, you probably want to have a barrel of 6″ to 8″ to get a lot of the additional power and still have it manageable. This barrel length will also give you a nice big sight radius for accuracy, making it good for hunting or target shooting.

How about for concealed carry? The shorter the barrel, the better, right? Well, if you look through all our data, you’ll see that usually, most cartridges see the greatest jump in velocity (and hence power) from 2″ to 4″. Now, the smaller the caliber and the lighter the bullet, the more the big jump tends to come right up front – from 2″ to 3″. The larger the caliber and the heavier the bullet, the more it tends to come a little later, from 3″ to 4″. Still, you can decide for yourself whether the trade-off in less power for ease of carry is worth it.

And good news for the revolver fans: because the cylinder basically functions to extend the barrel, your 2″ snubby actually functions more like a gun with a 3.5″ – 4″ barrel. Though there is some velocity/power loss due to the cylinder gap. How much loss? That is actually the next thing we’ll be testing, but I’d bet that . . . it depends.

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Since I wrote that six years ago, we’ve done a LOT more testing at BBTI, and have now shot more than 25,000 rounds and greatly expanded our data. The cylinder gap tests mentioned above did indeed show that the amount of loss did vary according to a number of factors, but for the most part established that the effect wasn’t as large as many people thought. And we found an interesting exception to the “magnum” rule in one of our most recent tests: it turns out that the .45 Super cartridge behaves like a true magnum, by continuing to gain more power the longer the barrel, until at carbine lengths it is on a par with (or even exceeds) the .460 Rowland cartridge. Since the .45 Super is based on the .45 ACP cartridge, we expected it to perform like that cartridge and level off at about 10″, but it clearly continues to gain out to at least 18″.

I also want to add a couple of quick comments about how concealed-carry guns have changed, though this is more just personal observation than any kind of rigorous research. I think that as concealed-carry has continued to expand, more gear is on the market to make it easier to do, and I think for that reason some people are able to carry slightly larger guns and there are more guns available with barrel length in the 4″ – 5″ range. In addition, sight/optics/laser options have continued to improve, making simple sight radius less of a factor — meaning that for those who do want to carry a smaller gun, it is easier to use it well (though having better sights/optics/lasers is NOT a substitute for practice!) I expect that both these trends will continue.

Jim Downey

Short and fun.

Another quick post about getting together for a bit of shooting weekend before last. This time, let’s look at some semi-auto carbines.

The first two are a pair of Beretta CX4 Storms, one in 9mm and the other in .45ACP. You can see them here with the pump guns:

I’ve previously reviewed the Cx4, and would only add that each time I shoot one of these guns I just enjoy the hell out of them. At just under 30″ overall length and weighing 5.75 pounds, they’re light, easily maneuverable, and very ergonomic. Great little pistol caliber carbines.

Now, see that gun partially visible off to the right in the pic above? And here’s another shot of it with the other pumps and carbines:

See that short little thing third from the left? Yeah, it’s an AGM-1 carbine in 9mm. Here’s a much better pic of it:

It’s an old-school bullpup, made in the 1980s in Italy. None of us had seen one before, and since it was a used gun it came with no paperwork or information. In picking it up, it felt almost too small to be civilian-legal (I mean non-NFA regulated), but the overall length is a tad over 26″ and the barrel is barely 16 and 1/8th inch. It has a little more heft than the Cx4, and most of the parts are heavy stamped steel. It uses Browning Hi-Power magazines. Interestingly, it was intended to be a modular design you could easily convert over to either .22lr or .45ACP, though I doubt the parts to do so are very common now.

But it was a surprisingly nice little gun to shoot. And when I say little, I mean it — damned thing is shorter than my arm. It was accurate, had a nice trigger, and almost no recoil. All of us were able to put a magazine full of bullets into a one-inch hole at 11 yards the first time we picked it up and tried it. Cool gun. If you ever happen to stumble across one in a shop, don’t be afraid to give it a try.

 

Jim Downey