Thread: .308 vs .30-06
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Old November 21, 2012, 09:01 PM   #64
Bart B.
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Join Date: February 15, 2009
Posts: 3,867
Rainbow Demon's comments:
Quote:
The OAL limit of the .308 means that when bullets of over 175 gr are used the bullet must be seated deeply into the powder space reducing effective powder space.
For this reason the .30-06 is capable of handing the heavier bullets such as 200gr and heavier long range match bullets with much less pressure penalty at higher velocities.

The 1:10 twist rate of most .30-06 barrels is better suited to the longer heavier bullets than the 1:12-1:14 twist of .308 barrels.
Match bullets up to 250 grains have been used in .308 Win. chambers with long throats. Muzzle velocity from a 28 inch barrel's about 2150 fps. Needed a 1:8 twist to stabilize them through 1000 yards, but was very accurate when David Tubb used it in the late 1980's.

Military rifle teams shot 190-gr. Sierra HPMK's from 22 inch M14NM barrels and 24 inch M1 barrels with their standard 1:12 twist. Excellent accuracy with such loads that pushed them out at about 2450 fps for the USMC Rifle Team load of 41 grains of IMR3031 in an LC M118 primed case for their M14NM's. The USN and USAF used 44 grains of IMR4320 under the 190's in the same case and got about 2600 fps in their Garands. Both loads had peak pressures not to far from blue pill proof test loads; much higher than standard specs for the 7.62 NATO round. Both loads had the best accuracy at 1000 yards of any used in these semi autos.

When the .30-06 was "the" round for high power match rifle use, 1:11 or 1:12 twist barrels were favored for bullets from 168 to 200 grains if best accuracy was the objective.

Starting in 1963 it took only 2 to 3 years of .308 vs. .30-06 for the .308 to become the choice for matches up to 1000 yards by top classified shooters. The .308's 40% better accuracy was more advantageous than the .30-06's 10% less wind drift.

Last edited by Bart B.; November 22, 2012 at 12:38 AM.
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