Barrel length vs velocity

[sobeit]

Years ago a gun mag did a series of tests on barrel lengths and velocity by taking standard rifles and shortening them an inch at a time. They recorded with a chronograph the velocity after each cut. The results were surprising , with some guns actually producing higher velocities with shorter barrels , eg...22mag optimum length was 19".  Question , is there any listing of optimum barrel length?  Notice that some are shooting a 45-70 w/ 32" barrels and others with 20". Now I would think the 32" was for sight radius...not velocity...

[tacklebury]

32" was also to be able to reach the long range targets with Black Powder cartridges.  I like the 32" because of using slower powders like Reloader7 also.    I believe that the shortest Sharps produced was 26" for the BP days.  As for accuracy, you will notice little even with iron sights out to 200 yards or so.  If you are talking scopes, I don't use em, so hopefully others will chime in on that side.  I know I've seen shorties here. 
 
p.s.  My BC will stay 32".  I might get a 22" barrel added just for comfortable hunting. 

[JMcDonald]

Id be surprised if rifle calibers didnt keep gaining velocity well beyond any practical or realistic barrel length.

[manatee1947]

Most of that has to do with the ratio of case capacity to bore diameter. There is very little increase in the 500 S&W from the 15" encore barrel and the 22" handi, and it uses pretty fast powders. Once you get into using 4831, RL22 and slower burning powders in large case small bore cartridges then barrel length of 26 to 30 inches become practical. 

[Dinny]

Here's some good reading:


http://www.ballisticsbytheinch.com/results.html




Thanks, Dinny

[JMcDonald]

Those are all pistol calibers and mostly with some generally mild loadings. Even then, handload with some slower powders (and without lawyer restrictions) and you really start to see the advantages of longer barrels. But yeah, for bottleneck rifle calibers I have no doubt that most of them would see peak velocities at 30" or beyond with select loads.

[manatee1947]

that shows me that H&R really, really, REALLY needs to put out a 16.5 Talo in 327 federal, handi grip version. That would have to be the greatest, most versatile small game / short range varmint gun ever made. I would take 2 .............

[sobeit]

One, not what I'm looking for....each cartridge has an optimum length...after a certain barrel length velocity decreases due to friction. With standard loads (factory) what is optimum length for a 17hmr, 22mag, 223,243, 30-06.etc..many think longer barrels are faster..not so....eg...on the 22mag velocity decreses after 19"....maybe I'll just write Hornady...

[JMcDonald]

I'd bet money that none of the larger rifle cartridges begin to lose velocity in a barrel shorter than 30". But, if you really want to know that bad, maybe you should go buy all the rifles and ammo yourself? Otherwise, you might have to settle for friendly internet discussion. In any case, since nobody produces rifles in common calibers with barrels that long (except special custom setups), even concrete data would be entirely academic. If you are just wanting to know whether or not a barrel you're looking at would be too long, don't worry, because it won't. Hell even "long" .50-BMG rifles have barrels of "only" around 32".
 
Here is some reading if you're interested:
http://www.loadammo.com/Topics/October05.htm
 
Here, you can see that in every loading but the lightest bullets, highest velocity was attained with barrel length over 40", with several of them achieving peak velocity from the full 46" length at the beginning of the test.
http://www.riflebarrels.com/articles/bullets_ballastics/long_barrel_velocity.htm
So, again, nobody is losing velocity by going to a 26" barrel over a 22", for example, except in rimfires or pistol cartridges.

[tacklebury]

The optimum length is going to vary by caliber AND load.  The optimum length = length of barrel in which all powder is consumed and stabilized accuracy is obtained in my opinion.  If your powder burns out quick and friction drags down the bullets speed.  If it's still burning as it leaves the barrel, it's a waste.  Finding the happy balance is the key.  I don't believe that if you used a High power load and a mild load in the same caliber, you'll ever have one perfect length.    Just my 2cp.

[JMcDonald]

Even after the powder reaction has ceased, there is still a great deal of pressure driving the bullet because the gas molecules are still at high temperatures and haven't gone anywhere. This is why a pistol-caliber rifle is still loud in long barrels, because even though the powder has all burned away (there wouldn't be any visible flash), there is still a great deal of pressure behind the bullet that is released upon exit, causing the report. Basically, the powder reaction has stopped well before velocities start to decrease (whether it is only a couple inches or a foot, I could not speculate).