Barrel length and speed


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layusn1
June 28, 2007, 10:49 AM
Is it longer barrels equal greater velocity or shorter barrels equal greater velocity? Thanks.

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BsChoy
June 28, 2007, 10:53 AM
longer is faster by about 25-50 fps per inch

layusn1
June 28, 2007, 10:57 AM
Wow, I didn't know there was an actual number to go with it. Thats cool, thanks. As always, THR members are a virtual plethora of knowledge.

Art Eatman
June 28, 2007, 01:57 PM
As a generality: For overbore cartridges like a .300 WinMag, the loss as the barrel is shortened can run close to 100 ft/sec/inch.

For mild overbore such as an '06, it's more like 75 ft/sec/inch.

For the shorter cases such as the .308 (and, I guess, the short magnums) it's more like 40 to 50 ft/sec/inch.

Art

Steve C
June 28, 2007, 02:42 PM
There is a general increase in velocity as the length of the barrel used is increased. This has to do with how much efficiency the gas being produced by the burning powder is used. There is a point at which there will be an optimum beyond which the velocity of the bullet will decrease with increased barrel length. This varies by cartridge and is dependent on caliber and case capacity.

The .22 LR for example has an optimum barrel length around 18.5" to produce maximum velocities. Rifles with longer barrels will shoot slower as will rifles with shorter barrels.

layusn1
June 29, 2007, 02:19 AM
Thanks again, I was looking for 223 specifically. Sorry for the double tap on the post. Switched to AT&T Uverse and it has been nothing but a pain in the (&(*& since we got it.

steve4102
June 29, 2007, 08:13 AM
Here is a barrel length test using the .223. They went from 22" to 10" in 1" increments.
http://www.accuratereloading.com/223sb.html

SlamFire1
June 29, 2007, 09:58 AM
You will find that for rimfires, the maximum velocity is acheived around 18" or so. There is just not enough powder in the case to keep accelerating the bullet.

Most pistol cartridges reach maximum velocities about the same barrel distance too.

And for rifle barrels, between my 308 caliber barrels, between 24" and 26", velocity is more dependent on the individual barrel than in the length. Some barrels just push the bullet faster, and the loads have to be cut.

Clark
June 29, 2007, 10:41 AM
The sensitivity to length in 22 rimfire is very sensitive to the ammo.

http://groups.google.com/group/rec.guns/msg/e42eef12685c9f8d?hl=en&lr=&ie=UTF-8

If you play with Quickload, you can see the effect that 223 barrel length has on fast powder and light bullets is much less than on slow powders and heavy bullets.

The effect the barrel length has on accuracy, noise, and weight are other things to consider.

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