Optimal barrel length for specific calibers?


June 20, 2006, 09:52 AM
Hey folks. I've been searching for some data that shows if there are (or not) optimal handgun barrel lengths for particular handgun calibers.

For instance, I read an article that said the 45 Colt can (relatively, that is) perform more efficiently in a shorter barrel than, say, a 44 Magnum. In other words, the author found that the 45 Colt wasn't as affected by a shorter barrel than a 44 Magnum.

Also, another source wrote that the 454 Casull gains almost nothing performance-wise when being fired from a 16" barrel (PUMA carbine, for example) vs from a 8" revolver barrel.

Anyone know of any studies on this? Any online resources out there? Anyone ever hear of anything like this?

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the naked prophet
June 20, 2006, 03:13 PM
That will depend almost entirely on the powder used. You can load up any case with a slow powder for a rifle, or a quick powder for a short pistol, so long as you stay within the loading data.

That said, bottlenecked cases and cases with more volume will do better in long barrels than other ammunition in those same barrels.

June 20, 2006, 11:22 PM
Generally speaking, the more powder you're buring, the longer the barrel needs to be. Most handgun cartridges have been designed to reach most of their potential in 4-6"; the bigger magnums tend to need more (7-10" is fairly common). Of course, all of them will gain some in a longer tube, but generally not enough to make the weight/size increase feasible. .25 ACP pistols are around 2", .32 and .380 guns usually come in around 2-1/2 to 3-1/2", 9mm and .40 S&W guns are generally 4", .45 and 10mm 5". Revolvers vary more, but most .357's are 4-6", .44's generally 6-8" and the .454/.460/.480/.500 are usually 7.5-10".

Optimal barrel length for a specific load can only be determined with testing (or a software program that I can't afford)

the naked prophet
June 21, 2006, 04:16 PM
Optimal barrel length for a specific load can only be determined with testing (or a software program that I can't afford)

You can't afford free?


June 21, 2006, 05:24 PM
Example for illustration:

It is possible to load .357 Magnum cases to levels that rival woods rifle rounds like the .30-30 and .35 Remington -- in a carbine-length barrel. The same rounds can be fired in S&W or Ruger revolvers, but they don't have anywhere close to the same velocity.

See http://www.buffalobore.com/ammunition/default.htm#357 for some commercially-available rounds that fit this description.

Note that there is not all that much difference between 3, 4, and 5 inch S&W revolver performance, though a 6" Ruger seems to add something. But stick those same cartridges in a Marlin carbine, and wham-o, they turn into rifle rounds.

These are NOT standard loadings! And you won't see the same deltas with a lot of commercial .357's. What I'm trying to demonstrate here is that there is an optimal barrel length for a given LOADING of a given cartridge, but it's very difficult to generalize about a caliber.

June 23, 2006, 01:25 AM
Powder selection (burning rate) is NOT based on barrel length. Burn rate is selected on the basis of a). the relative weight between bullet weight and powder weight, and b). the relative pressure level desired.

Effeciency is based on expansion ratio; the comparitive size of burning chamber and size of chamber and interior of bore. (The greater the number, the more times the chamber pressure expands, the more energy is imparted to the bullet.)

The .45 Colt performs more efficiently in a smaller barrel than a .44 Magnum is the .45 Colt runs at lower pressure; each inch of barrel does not impart as much velocity as does the higher pressure of the .44 Magnum. However, do not confuse 'efficiency' with total horsepower. In equal barrels, the .44 Magnum will go faster than the .45 Colt in any bullet weight. The .45 Colt doesn't have as much to start with and so loses less as the barrel is shortened. 'Efficiiency' in this case is simply a greater deliver of velocity per grain of powder used. Just for the record, .32-20 Winchester is more efficient than both.

Any cartridge will deliver more velocity (all other factors being equal) with a longer barrel. However, the point of diminishing returns arrives fairly quickly; not to mention practical considerations.

Old muzzle loaders routinely had barrels of 30 to 40 inches. Up until not too long ago, shotguns had pretty long barrels. Then again, it wasn't a problem; no one had a car or pick up truck in which to pack the long gun. Mounted on a horse was not a big deal for a long (relatively) barrel. (Not to mention black powder burns differently.)

However, smokeless powder and society changed things. Guns needed to fit in back seats or trunks. Handguns had to be - discrete. Smokeless powder gives a better push than black.

And of course, a pistol with a twenty inch barrel is awkward at best.

Is there a 'best length'? Probably. But it more than like varies with intent. Load density certainly has some bearing on the matter.

I'm running out of steam. There's more to this, but I have to sleep anyway.

June 23, 2006, 09:59 AM
I understand the logic presented that there is a optimal barell legth for a given load, but not a given caliber.

But if you take "custom" loading out of the picture, is there enough similarity in say....9mm self defense factory loads, or .357 factory loads, that you could pin down an optimal barrel length?

June 24, 2006, 12:01 PM
One of the most tested standard loads in the world is the 9x19 (9mm Parabellum, 9mm Luger, 'Da 9' and so on). Typically, this load is a 125 grain FMJ at about 1200 fps. (Yes, there are other loadings.) The original 9x19 pistol, the Luger, was I think a 6" barrel gun. However, 9x19 is now used in everything from derringers (less than 2") to 16" barreled carbines.

The longer barrels shoot faster.

However, many modern belt guns are in the 3.5" to 4.5" range. The Glock 17 currently on my belt is 4 3/8 inches (I just measured it, honest.) The trade off is the moderate length barrels are handy to use and holster. I don't think a 5" gun would be markedly more awkward, but somewhere between 5" and 8" would be getting unhandy.

.38 Special is another well documented round. 158 grain RNL (or SWC) at about 800 fps. I think the first guns - about 1898 or so - were 6" revolvers. Again, .38 Special has been used in everything from 'glorified chambers' to carbines.

The longer barrels shoot faster.

But again as in the case of the 9x19, a 2" Chief Special is easier to hide than a 1892 Winchester. A 6" K38 is more accurate (that is, is easier to shoot accurately) and gives more velocity than a Chief Special. A '92 Winchester is more accurate and gives more velocity yet.

I think the problem here is the word 'optimal'. If we're discussing a theoretical interior ballistics problem wherein we are attempting to completely burn all the powder used and gain maximum efficiency from the powder used, we can do a lot of testing and cut off a lot of barrels in the process.

The late Jimmy Clark, Distinguished Pistol shot and target pistol builder extraordinaire thought the 'optimal' barrel length for a target pistol was about three inches. His reasoning was that was enough to get the bullet spinning properly, impart enough velocity to penetrate paper at 50 yards, and be gone quickly enough so the shooter's 'follow through' was as short as possible. I've had another excellent shooter tell me a .22 long rifle target pistol has to have a minimum of 4" of barrel to properly launch a .22 bullet for accuracy at 50 yards.

Or, one could attack it from the perspective of a defensive handgun that is long enough to get decent horsepower and short enough to be handy. Three to four inches on a .357 revolver makes for a really fast handling fighting gun.

So, what do you mean by 'optimal' when you ask the question?

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