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Old November 3, 2012, 09:39 AM   #14
Bart B.
Senior Member
Join Date: February 15, 2009
Posts: 6,318
While duplicating a given load's muzzle velocity is oft times the "objective" of lots of folks believing that it's the sure way to get its accuracy, nothing could be further from the truth. Best example's when Federal GMM .308 ammo's been chronographed in several rifles all shooting it well under 5/8 MOA at 600 yards, muzzle velocity spread across those barrels was over 60 fps. This is what some of us learned chronographing it in several M1 and M14 barrels. One lot of that ammo shot at least that accurate in three of my .308Win. bolt gun barrels and there was a 45 fps spread in its average muzzle velocity.

I used the same load across nine or ten .308 Win. barrels with the lot numbers of powder, bullet, powder and primer all being diffefrent. They all shot about 1/3 MOA with 168's through 300 yards, about 1/2 MOA at 600 with 180's, 190's and 200's and sub 3/4 MOA at 1000 with 190's and 200's. The same lot number and charge weight of IMR4320 across different lots of 7.62 NATO M118 primed cases was used in my handloads for Sierra 190 HPMK's across four barrels in Garand M1's; they all shot about 2/3 MOA at 600 yards and about 1 MOA at 1000.

Dan Newberry, I wish I still had the Federal brass .308 Win. case I reloaded 47 times with 42 grains of IMR4895 under a Sierra 165 SBT atop Federal 210 primers that was fired in a tight bore Hart barrel; definitely a maximum load. Primer pocket didn't open up and never annealed the neck once. Muzzle velocity spread was about 30 fps across all shots that went into 3/4ths inch at 100 yards. Friend of mine got 56 loads on his .308 Win. Federal brass case using the same load under Sierra 168's; they all went into 1/3 MOA fired in his machine rested match rifle at 100 yards.

I'm convinced that with new, unprepped .308 Win. cases of reasonable quality, 44 grains of IMR4064 under a Sierra 168 or 43 grains of it under a Sierra 175 or 180 using any decent primer and assembled decently, one will easily get sub 1/2 MOA accuracy from a decent rifle properly tested at 100 yards. If not, check out the rifle or the shooter's technique. Sierra does not work up loads for testing their bullets when changing lots of powder, primers or cases; their best 30 caliber match bullets go into 1/4 MOA at 200 yards.

Last edited by Bart B.; November 4, 2012 at 07:08 AM.
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