Long Range Barrel Lenths

[l3uddha]

for a long range rifle in 7.62, what do you see as the best barrel length? does 24 inches make a world of difference over 20 inches in terms of accuracy and velocity?

 

[Mike S]

What do you consider long range?

 

[jasons]

You should get a barrel that's 1,000 yards long. You'd be a shoe-in on the 1,000 yard line.

 

[crazymjb]

7.62Xwhat? I assume 39?

Mike

 

[Supermoto]

7.62Xwhat? I assume 39?

Mike

when people say 7.62 and long range, nobody means x39.

 

[l3uddha]

What do you consider long range?

I'm talking the more theoretical sense, moreso what range I'd actually shoot and be anywhere close to my target.

7.62Xwhat? I assume 39?
Mike

7.62x51... should have been more specific. I'm looking at the Remington 700 line... .308, which I think is the rough equivalent of the 7.62x51. I see the XCR model actually has a 26 inch barrel...

 

[JohnFH]

The majority of people shooting 600yds plus with 308 are using 24" or longer barrels.

 

[PantherarmsAR10]

It also depends on the grain of bullet and the length of barrel with twist rate

 

[Quinn800x]

I also have been wondering this question. Ive been looking at a Savage 10 fp with a 20'' barrel. Twist rate is 1/10'. Do you think this rifle has the ability to put them on a target @ 600yrds or will a 24'' barrel make the difference?

 

[JohnFH]

I also have been wondering this question. Ive been looking at a Savage 10 fp with a 20'' barrel. Twist rate is 1/10'. Do you think this rifle has the ability to put them on a target @ 600yrds or will a 24'' barrel make the difference?

Short answer yes. Consistency is the key to accuracy. I went with the 24". Way to much for me to go into here, (would take me days 2 finger typing) but look at the long distance shooting sites, there is plenty of published info.

 

[oneswithfunes]

Velocity is pretty much the only factor regarding length. Shorter barrels handle a lot better but that is it. Anyone who thinks they are less accurate should shoot some more. I shoot a 28" on the 308 but I am trying to get every bit of speed I can for the 208 amax.

 

[Madball13]

Military, not sure what branch, will be changing the bolt sniper gun in .308 to a 20" barrel with a change in twist rate.

 

[oneswithfunes]

Military, not sure what branch, will be changing the bolt sniper gun in .308 to a 20" barrel with a change in twist rate.

So the guns handle better. Has nothing to do with accuracy.

 

[l3uddha]

So the guns handle better. Has nothing to do with accuracy.

going from 24" to 20" to handle better... what do you mean by that? ballistics-wise, or do you mean that it's just easier to crawl around with a shorter rifle?

 

[whatluck]

Well, a longer barrel will add a few hundred FPS right? Won't that affect bullet drop and effect of wind on the trajectory?

 

[PatMcD]

Barrel length has no meaningful bearing on accuracy, except when you are shooting iron sights. In that case, the longer sight radius helps the shooter shoot the rifle more accurately.
Barrel length does help with long range (600+ yards) in that you can get more velocity. You don't need velocity because of trajectory. You need it because a faster bullet is better in the wind.

 

[lupis42]

Barrel length has no meaningful bearing on accuracy, except when you are shooting iron sights. In that case, the longer sight radius helps the shooter shoot the rifle more accurately.
Barrel length does help with long range (600+ yards) in that you can get more velocity. You don't need velocity because of trajectory. You need it because a faster bullet is better in the wind.

Barrel length does affect accuracy in one other way: a longer barrel is less rigid than a shorter one, and so flexes more under the stress of firing, reducing accuracy slightly.

 

[PatMcD]

Barrel length does affect accuracy in one other way: a longer barrel is less rigid than a shorter one, and so flexes more under the stress of firing, reducing accuracy slightly.

I said "no meaningful bearing on accuracy". In theory, you are correct, but I don't think it can ever be shown on target.

 

[bpm990d]

I have a 30 inch barrel on one of my Winchesters. Long barrels will get the most out of large charges of slow powder. Some Palma shooters have 32 inch tubes.

B

 

[oneswithfunes]

Barrel length does affect accuracy in one other way: a longer barrel is less rigid than a shorter one, and so flexes more under the stress of firing, reducing accuracy slightly.

Barrel rigidity decreases with the 3rd power of length and increase in rigidity with the fourth power of their outside diameter. The amount of barrel deflection between 18" and 24" mtu or heavy varmint contour is some where on the order of .0005 and .002 respectively. D=(W*l^3)/3*E*I if you would like to calculate it. Really just a cantilevered beam. Yes it is real and you can measure it, does it have a affect on accuracy? Not really. Barrel length in no way affects real world accuracy. Saying irons matter has no real bearing. The added sight radius is a side affect and does nothing to change the accuracy of the barrel .

 

[lupis42]

Barrel rigidity decreases with the 3rd power of length and increase in rigidity with the fourth power of their outside diameter. The amount of barrel deflection between 18" and 24" mtu or heavy varmint contour is some where on the order of .0005 and .002 respectively. D=(W*l^3)/3*E*I if you would like to calculate it. Really just a cantilevered beam. Yes it is real and you can measure it, does it have a affect on accuracy? Not really. Barrel length in no way affects real world accuracy. Saying irons matter has no real bearing. The added sight radius is a side affect and does nothing to change the accuracy of the barrel .

Fair enough.

 

[oneswithfunes]

Just something that is applicable to what I do and I find interesting. Dan Lilja has some very good papers on the subject.

 

[bpm990d]

Barrel length does affect accuracy in one other way: a longer barrel is less rigid than a shorter one, and so flexes more under the stress of firing, reducing accuracy slightly.

Most of the short range BR shooters have fairly short barrels for that reason, but I think most of the 1000 yard BR shooters are taking to the line with very long barrels. At a certain range, the very real increase in velocity gain makes up for any theoretical loss of accuracy. A couple hundred fps increase in velocity will make a difference in wind.

Varmint Al's webpage has some FEA (finite element analysis) of barrel harmonics. If the load has the bullet exiting from the top or bottom of it's vibration oscillation, then long barrels can be very accurate at longer ranges. However I don't think they would work at point blank bench rest. Probably not accurate enough to win.

B

 

[oneswithfunes]

Most of the short range BR shooters have fairly short barrels for that reason, but I think most of the 1000 yard BR shooters are taking to the line with very long barrels. At a certain range, the very real increase in velocity gain makes up for any theoretical loss of accuracy. A couple hundred fps increase in velocity will make a difference in wind.

Varmint Al's webpage has some FEA (finite element analysis) of barrel harmonics. If the load has the bullet exiting from the top or bottom of it's vibration oscillation, then long barrels can be very accurate at longer ranges. However I don't think they would work at point blank bench rest. Probably not accurate enough to win.

B

It should be there in the first place due to proper load development. Thanks for that link. I had not seen it.

 

[JohnFH]

If the load has the bullet exiting from the top or bottom of it's vibration oscillation

That is the reason we do "ladder testing" during laod development, to find the "sweet" spot in the harmonics and try to have the bullet leave the barrel at the transition point between going up and down where there is a momentary pause.

 

[bpm990d]

I agree. I've also seen some weird things that I think are related to this. Taking a barrel that wont shoot with a whole bunch of loads, and cutting a inch off of the barrel. Suddenly it's a tack driver. It was probably a vibration thing.

B

 

[Madball13]

So the guns handle better. Has nothing to do with accuracy.

Well seeing as though it's for a sniper rifle handling will of course be better and they obviously feel they can maintain the same accuracy standards with a 20 inch barrel.

 

[oneswithfunes]

Well seeing as though it's for a sniper rifle handling will of course be better and they obviously feel they can maintain the same accuracy standards with a 20 inch barrel.

Are you implying there is a accuracy component to length?

 

[Madball13]

Are you implying there is a accuracy component to length?

Nope, i'm implying the experts are looking to get the job done with a 20" barrel.

 

[oneswithfunes]

Cool. I am a little slow sometimes.