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Old May 11, 2005, 10:53 PM   #7
Unclenick
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Join Date: March 4, 2005
Location: Ohio
Posts: 10,475
Smokey Joe has a good point. You can work up loads with identical velocities with no problem (though you should get at least one box of the Federal to compare with what you work up over your chronograph; some are more accurate than others, so you want to match readings on THAT chronograph if you can do so without seeing pressure signs with your test powder).

I like Varget in .308. IMR4895 and H4895 require enough powder to increase the pressure almost 10% to achieve the same 2600 fps from a 22 inch barrel. In a Federal case (55 gr. water capacity level with the case mouth) using a Federal 210M primer, 42.7 grains of Varget comes out about right in my M1-A, but you should start at 40 grains and work your way up, checking for pressure signs. In the immensely strong Garand-style action, you are unlikely to run into trouble, but watch for primers getting too flat.

I've also had good luck shooting the 168 grain Sierra MK with 43.5 grains of AA2520 in that gun. But ball powders are harder to light up, and I discovered I had to use the bench rest shooter's trick of deburring the flash holes in my cases to get best accuracy. It brought 100 yard, slow-fire prone groups down from 1.5" in 0.75" firing 2520. Deburring flash holes did nothing for the more easily ignited stick powders. You can get a deburring tool from Sinclair.

I went through Gunsite's PR1 class with a tac rifle PMC .308 match loaded with the 168 grain Sierra MK. It’s a good approximation of the Federal product. It worked fine, except on a popper 748 yards out across a valley with a strong cross-wind. Nobody shooting the 168's could hit it consistently. Two years later I found out why.

It was the first time I attended the Long Range Firing School held every year at the end of the National Matches at Camp Perry. I and numerous other cursing people had come loaded with the Sierra 168's, and from short range (800 yards is short range at that school) got a lot of complete misses. Guys in the pits reported back numerous keyholes among the shots that stayed on the paper.

It turns out that when the 168 drops sub-sonic (about 700 yards for match ammo) it gets very unstable. Sierra’s Chief Ballistician, Kevin Thomas also happened to be attending the LRF school that year and said the 168’s had been designed for 300 meter international competition originally, and that it turned out they work well at 600 yards for Service Rifle matches was a happy bonus for Sierra. Their newer 175 grain MK, however, is designed for longer range ballistics and doesn't exhibit this behavior. The next year I went back to the school with the 175's loaded and shot a 99 on the first 800 yard target. No problem there or at 1000 yards (shooter errors not withstanding).

The lesson is, if you go out beyond 700 yards, change to the newer bullet or don't take the shot. That may never be a consideration for you, but I thought I would toss the heads-up out there just in case.

Nick

Last edited by Unclenick; May 12, 2005 at 07:29 PM.
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