Re: FGMM .308 vs FGMM 7.62x51
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: KillShot</div><div class="ubbcode-body">[snip]
I know the SAMMI pressures are different (65,000 vs 50,000) and the 7.62x51 is a thicker casing but is there any difference in accuracy that anyone has found?
Thanks for any info you can give.
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Um, the sources I have show that even when both SAAMI and USGI were measured with copper crushers, there were differences in methodology which made the numbers NOT identical. One was tested with a hole in the case wall under the piston that drove the copper pellet, while the other used intact cases. Forget which was what and what effect it had.
Same for the 5.56mm/.223 nonsense, which is really just a difference in chamber throats and allowable bullet ogive profile beyond the case mouth. That was the result of going for a heavier bullet and slightly better BC when the military finished its development, as compared to the short light speed-demon bullets used in the prior .224-diameter varmint cartridges just before the then-new SCHV project gave us M193 ammo. Pressure-wise, IIRC the 5.56 is measured with a piezo sensor just in front of the case mouth, while SAAMI piezo puts the transducer at mid-body of the case.
Or something like that.
Then of course there are the problems of comparing 7.62 NATO CUP numbers from the 1950s adoption of the round, with modern SAAMI piezo numbers. Cross-referencing data points can be a booger.