Re: Puget Sound Area Shooter's Group
Bigwheels,
So far, the only bullets I have run through my 300 have been Sierra 190's, and Lapua 185 Scenar's. Both seem to have about the exact point of impact out to 600 yards. I haven't tested them beyond that.
My 300 was built by Gale McMillan (started McMillan rifles) back when he was still alive. I asked him where to begin looking for a good load, and he said he can give me the exact recipe...
Winchester cases
Federal 215M primers
70 grains of IMR4350
190 Sierra Matchking
That load worked fabulous, but I found I got the same accuracy with 68.5 grains, and I figured it wouldn't be quite as hard on brass and barrels.
So far, I have gone through the original McMillan barrel, two Schneider 1-10 twist polygon barrels, and am now on an Obermeyer 1-11 5R barrel that was set back 1.5 inches at the breech, and had .5 inch cut off the muzzle about 350 rounds ago. I had it set back at about 850 rounds because I didn't want to risk really cooking the throat before I set it back.
The tube is now 25 inches long from the front of the recoil lug. I guess for most people they would call that a 26 inch barrel if measuring from the gas vent on the right side of the receiver. I also had a muzzle brake with 4 large baffles designed specifically for this rifle mounted onto it. Recoil is about the same as my TRG22 (308), but it most certainly has a much sharper "bark" to it.
The 260 Remington has a 27 inch barrel (again from the front of the recoil lug) so I can have it set back when necessary, but it only has around 900 rounds through it.
My next loadings will be with either the 208 or 225 grain bullets and the H1000 powder you recommended. My only concern is whether my 1-11 twist barrel will stabilize that heavy of a bullet adequately. For what it is worth, my 68.5 grains of IMR4350 gets the 190's going 2960-3000 fps depending on ambient temperature. If it is really hot out (90F and above) I get a little nervous when the ammo warms up and pressures increase.
Let me know if you think the 1-11 twist will stabilize the heavier bullets properly. I note that Sierra recommends a pretty fast twist for the 210 grain MK, but they don't have the same notation for the 220....I guess the 210 is much longer, hence the warning.