Barrel Length Question

[LHClarke]

Hey folks. I am about to build another rifle and am wondering about "real world" difference in velocity between the 18" (Middy gas) and the 20" (rifle gas) length barrels.

I know it depends on what I want the rifle to do etc, etc.......BUT has anyone had the opportunity to chrono these? I guess it's a difficult question because of all the variables involved. I don't need an exact to the f.p.s. answer.

I guess my real question is: "Will the 18" barrel be combat effective at 800 meters?" I have to think that it will be looking at the ballistic data on AA's site. I am just wondering if the extra 2" is worth the weight and length I guess. Any insight is greatly appreciated.

LHClarke

[VASCAR2]

Every thing I've read indicates you loose about 30FPS per inch. So your 18" will be in the neighborhood of 60 FPS slower than a 20" From the chronograph results I've seen with 16, 18 & 20" barrels using the same lots of ammo this seems pretty close. I think the loss is higher once you get less than 16" especially when you get down around 10" barrel. When you get over 28" to 24" the loss might actually be a little less than 30 FPS and inch because most of the powder is completely consumed and drag can slow a projectile.

[LHClarke]

Thank You for your response. It's a silly question I suppose. This lines up with what I've heard and read with other calibers and platforms. Sometimes you just need to "hear it" again to feel confident with the decision that is being made when your about to drop major coin to build a rifle.

LHClarke

[LR1955]

Every thing I've read indicates you loose about 30FPS per inch. So your 18" will be in the neighborhood of 60 FPS slower than a 20" From the chronograph results I've seen with 16, 18 & 20" barrels using the same lots of ammo this seems pretty close. I think the loss is higher once you get less than 16" especially when you get down around 10" barrel. When you get over 28" to 24" the loss might actually be a little less than 30 FPS and inch because most of the powder is completely consumed and drag can slow a projectile.

VC2:

I have tested it from 20 to 28" barrel lengths and it is pretty consistent at about 30 fps per inch.

LR1955