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>308 Barrel Length

 
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  #15  
Old 06-01-2010, 11:08 AM
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Join Date: Feb 2009
Location: Sedalia, MO
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Re: >308 Barrel Length

Davkrat,

Fine on the computer, not so fine (usually) in real life. The 2800 fps you cited won't cut it with the 155s @ 1000 at most ranges. Palma shooters normally run a minimum of 2950 fps for this bullet, and that will pretty much assure 1K performance with a little margin for error. The also shoot 29-30" barrels, and are running max loads even then. Out of a 24" bbl, the 2800 shouldn't be a problem, but that 2950 mark is gonna be real tough, and I don't want to stand too close if you make there, if you get my drift. Given the shorter barrel, you'll be better off going with a heavier bullet, like the 175 SMKs or 180 VLDs. Get those up to around 2650, and they'll stay supersonic at 1K, no problem.

Hope that helps,

Kevin Thomas
Lapua USA
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  #16  
Old 06-01-2010, 12:00 PM
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Join Date: Dec 2005
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Re: >308 Barrel Length

Quote:
Originally Posted by ernierod View Post
Thanks people for all the good advice. I will be shooting up to and occasionally 1,000 yds. I am thinking Remington 700. Will have a choice between SPS/26"/Heavy bbl-1:12 twist OR Rem 700SS Milspec 5R type rifling-24"-1:11.25 twist. I am aware that, most likely, the 1:10/1:11.25 twist will handle heavier bullets better than the 1:12 twist bbl but I am a beginner in LR shooting and don't really know how important heavier bullets are to the long range-(700+ yards) shooting in the accuracy department.Thanks for opinions. Erod
Note that heavier bullets in any cartridge make it harder to shoot accurately. This is why many top long range competitors quit using Sierra 190's in favor of the 155. With less recoil, the rifle moves less when the bullet's going down the barrel.

Optimum twist rates for Sierra's 30 caliber match bullets from a .308 are:

135 gr., 1:14
150 & 155 gr., 1:13
168 & 175 gr., 1:12
180 & 190 gr., 1:11
200 gr., 1:10
220 gr., 1:9
240 gr., 1:8

I wouldn't spin any bullet any faster than what stabilizes it. Any more will cause excessive jump of the muzzle axis as it exits the barrel. This is caused by the slight imbalance all bullets have and the centrifugal forces they have is quite a bit. Well, there may be 10 in a box of 100 that are perfectly balanced, but you'll need a tool to spin them a few dozen thousand RPM's plus a sensor to detect the unbalanced ones; all without damaging the bullet.

Friend of mine tested some 30 caliber match bullets for balance and kept those few that were perfect. Shot from a .308 Win. at 600 yards, most of the 10-shot groups were 1.25 inch and smaller, some around .75 inch.
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