Ricochet

Your rpm for that load you shot from your 300 mag rifle is 165,000 rpm. The formula is 2200 fps (your muzzle velocity) time 750 (a constant) divided by your rifling twist 10 equals 165,000.

That was a pretty good group I thought, especially for just shooting in near dark and right after firing jacketed.

Joe

Thanks, Joe!

Here's what he's talking about, that I posted over on Cast Boolits: (There's been a lot of discussion over there about RPM primarily limiting cast bullet velocities and accuracy.)

This is the best I've been able to do with Aladin's HBC boolit. Look at that vertical stringing, makes me sick!



In case you can't read the fine print, that is at 100 yards from my .300 Weatherby Magnum Vanguard, with 4.3 cc of 7383, bullets cast of WW and oven heat treated (close to a year ago), sized .311", lubed with a 2:1 mixture of JPW and LLA. Primer is CCI #34, and they're crimped in with a Lee Factory Crimp Die. MV is a little over 2200 FPS. (Dunno what the RPMs are with that in a 10" twist.) I only shot this one group the other day as it was too dark to see the holes in my rifle scope or spotting scope, I'd just switched from shooting 2" 200 yard groups with 180 grain Hornady Spire Points and popped these off right quickly through a hot dirty barrel. Couldn't see to shoot any more after these three. Is a three shot .641" group under these conditions a fluke? Probably. But I'll take it and see what I can do next time. I've shot a few of these before and seen 1 1/4" 5 shot grouping. This is one of those low pressure, large case capacity, long pressure curve loads that gets good velocity without overstressing the bullet.

You welcome John.