The title pretty much is the whole article. If you want to shoot a gun with a short barrel, get one that shoots a short cartridge. Using a long cartridge has a big energy drop in short barrels.
The key concept is: Case volumes of expansion.
If your case is an inch long, a 10 inch barrel gets almost all available energy.
A 5 inch barrel does OK with more muzzle flash and noise. At 2 inches, most of the available power in the powder goes into noise and flash, bullet energy not so much. Make that case 1/2 inch or even less, efficiency in short barrels goes way up.
This comes into play in several very common cartridges, and not always in a good way. Most revolver cartridges were designed in the black powder era. It is bulky. Smokeless powder then left much of the case empty. Magnums then made the cases longer to avoid folks putting them in non-magnum guns. This made things worse. Now you have a long shell without much powder in it. (Yes, you can load bulky powders and fill it up, but compare the .357 Magnum case with the .357 Sig case and remember the Sig is the same power as some of the regular magnum loads.) Or compare the .38 Special case with the more powerful 9mm case. Were I getting a short barrel revolver, I’d look for one that shoots a round like the 9mm or .45 ACP.
How short it short? It varies with the cartridge, but under 4 or 5 inches.
This also shows up when folks talk about comparative muzzle energy of pistol rounds, especially if one of them is a .22 LR or Magnum that are usually measured in an 18 inch barrel, not a 3 inch snub nose. You must compare rounds from the same short barrel length. Lucky for us, there’s a web site that’s done just that.
Welcome to Ballistics By The Inch, or ‘BBTI’ as people have taken to calling it.
Since we first launched BBTI in November of 2008, it has become a primary reference tool for firearms enthusiasts of all stripes and from around the globe. Our initial research data covered the relationship between barrel length and velocity for some 13 common handgun calibers/cartridges. In response to the phenomenal popularity of the site, we’ve continued to do testing, and have expanded the data to include an additional 8 handgun calibers/cartridges (and a repeat of the .380 Auto tests with additional ammunition) as well as the .223 rifle cartridge. We’ve also conducted a major study of the ‘cylinder gap effect’ on a revolver, involving more than 6,000 rounds fired, as well as a comparison of the performance differences between polygonal and traditionally rifled barrels. As always, all of our data is freely available, though we happily accept donations (see button below left)and would greatly appreciate your tangible support to help us continue the project.
Up above you’ll find links to four main pages:
Calibers/cartridges will take you to a list of all 22 different data sets. You can just browse the charts, click on a given ammunition type listed in the header of each chart for a graph of how that particular ammunition performed, or download the raw data for your own use.
So let’s look first at a short lower pressure cartridge, the .45 ACP:
Ignoring the bottom line “low recoil” round and the extra power top lines, look at the more common Federal standard pressure orange line. Starts at about 440 and ends about 330. more than enough power even from a 3 inch barrel.
Compare the rate of energy fall off with a longer case round, the .22 Magnum:
By the time you are down to a 3 inch barrel, your 300+ ft-pounds are down to 80. About the same as a .25 ACP round. Even from a 5 inch barrel, half your energy is going to noise and flash. 160 ft-lbs is about the same as a standard .380 or the CorBon hot .32 ACP, yet folks talk down the .32 ACP and praise the power of the .22 Magnum even in short barrel revolvers (some in the 2 inch range).
This, BTW, is why I’m quite happy with my very short case .22 SHORT, .25 ACP, and .32 ACP rounds in my 2.x inch barrel Berettas. They don’t have a graph for the .22 short, but it is over 1000 ft/second and will hold that kind of speed even in short barrels. It ought to be close to the .22 Magnum in the 2.x inch range, but without the obnoxious noise and flash. I eyeball the barrel at about 7 case volumes of expansion for the .22 short. Enough to be fairly efficient. The quiet shooting confirms most of the energy is in the bullet.
List power is about the same in their test barrel, and with the extreamly short case, most of that will be available in the very short barrel.
Bullet mass/type Velocity Energy
27 gr. (1.8 g) RN 1,164 ft/s (355 m/s) 87 ft⋅lbf (118 J)
What about the .22 LR? As you might guess ftom a name with “rifle” in it, not so great:
So about 50 to 70 ft-lbs in a 2.x inch barrel. Or about what the short is giving you. Even in the 4 to 5 inch barrel range common in guns, you get in the 50 to 100-ish ft-lbs range.
Here’s the .25 ACP and .32 ACP:
Even in the 2 inch barrel, 75 ft-lbs. 3 inch bounces you up to 75 to 90 depending on ammo, and at 5 inches it is up to 100 ft-lbs. Better bullet construction and more reliable primer too. Oh, and less blinding flash at night while being quieter too. This from the widely poo-pooed as “don’t even think about it” .25 ACP from the same folks who praise a .22 Magnum mouse gun.
But lets go upscale to the .32 ACP:
Solid 100+ ft-lbs even in 2 inch barrels. Up to 175 with CorBon in a 4 inch barrel. My Walther PP has a 3.9 inch barrel, so it will get that.
Next, the .380 and .38 Special / .357 Magnum / 9mm:
Ignoring the +P rounds, its about 125 to 150 from 2 inch to 150 to 175 in a 3 inch. Now tell me again why a 3 inch barrel 380 is going to be so much superior to my .32 Walther PP?
The snub nose .38, classic Detective’s gun in the movies, is running 110 to 175 ft-lbs. Gee just about the same as high end ammo in .32 ACP in th PP. A poor choice of ammo and that 110 is less than any of the .32 ammo graphed from the PP. Yet loads of folks will claim a .38 snubby is enough gun and a .32 isn’t. Those are folks ignorant of the relevant math, physics and data. Move up to a 4 or 5 inch barrel, then they have a case to make for 250 to 350 ft-lbs being more.
How about that Killo-ft-lb .357 Magnum? How does it do in a pocket gun?
About 200 to 300 ft-lbs (and 700 ft-lbs worth of flash and bang!) Furthermore, it is already dropping fast even in a 10 inch barrel! By 4 inch, the starting 1200 ft-lbs is down to 600. Why I like it in my Marlin rifle and why my pistols are long barrel 6+ inch.
Compare the flatter 9mm Lugar curves:
With +P giving over 300 even in a 2 inch barrel. MORE than the .357 Magnum. By 4 inches, you have 300 to 450 even with standard ammo. Hot ammo in a 4 inch barrel 9mm still beats the .357 Magnum 3 inch! (And is just middle of the pack of the .45 ACP from a 3 inch barrel…)
Also the .357 Sig, a necked down .40 S&W:
Almost 500 ft-lbs from a 3 inch barrel and matching the .357 Magnum in 4 inch with flatter curves.
Just for completion, here’s the graphs for .40 S&W and 10mm. Note that with a 4 inch barrel, the 10mm is about 50 ft-lbs more power. 10%. 450 vs. 500 more or less. Yet there are folks who scream about the .40 being a bastard underpowered 10mm and how much better the 10 is. After all, it has way more kick and noise… But at least now you know why the FBI was OK with dropping the 10mm for the .40 S&W. The smaller case is just more efficient. Ammo choice can matter more.
Also note that the .40 S&W 4 inch is about the same as the .357 Magnum 3 inch and the .45 ACP 3 to 4 inch.
When you get below about a 5 to 6 inch barrel, you need a short stubby case to give enough case volumes of expansion to the gasses and efficiently make your bullet energetic. Long cases like old revolver rounds are just throwing away energy below that length. I’d rather have a 4 inch barrel revolver in a semi-auto round like the .45 ACP or 9mm than in .357 Magnum.
Considering this, IMHO, there’s real room for energy improvement in revolvers by designing brand new cartridges that are fat and short.
Or just get one chambered in .45 ACP and be done ;-)
In mouse guns and things with sub 3 inch barrels, the “dinky” cartridges originally designed for them, like .25 ACP, .32 ACP and .380 Auto are far more efficient than long skinny cartridges and can often beat them for total power. Ignoring case length and just looking at published max power numbers from long test barrels (often 10 to 18 inches) is very misleading, yet is usually what is done.
Remember that when it comes to barrels, bigger IS better! But for cartridges, you want shorter in handguns.