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Old April 16, 2012, 10:09 AM   #34
Bart B.
Senior Member
Join Date: February 15, 2009
Posts: 6,318
OSOK, back in 1991 when Sierra Bullets' finished their prototype Palma bullet, a 30 caliber, 155-gr. HPBT match bullet, I and half a dozen other former US Palma Team members were asked by the Team coach to develop a good load for it. We had to use new cases weighing about 170 grains, Federal 210M primers, any powder we chose and were given a 1000-round box of bullets. All powder charges had to be metered; exact weights were not allowed as two Dillon 1050 progressives would be used to load a few hundred thousand rounds of it. 20-shot groups at 1000 yards was the test.

We used both extruded and ball powders with medium burning rates; IMR 3031 and 4895 and similar. After we all shot a few dozen 20-shot groups with all sorts of powder, 45.3 grains of IMR4895 was picked. It didn't produce the lowest spreads in metered charge weights, muzzle velocity and peak pressure as tested in a lab, AA2520 did that by a decent margin. But AA2520 produced the worst accuracy and the other ball powders tested were also near the bottom of the accuracy list. IMR4895 metered to a 3/10ths grain charge weight spread but shot well under 1/2 MOA at 600 properly tested for accuracy.

Even more interesting was when that ammo was first used in an international long range match later that year, top shooters from around the world reported it shooting 1/2 MOA at 600, too. Not too shabby for doing well in a wide range of barrel contours plus a variety of chamber, bore and groove dimensions.
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