My 300 win seems to love 75 grains of H4831sc with 180 Horn. BTSP in win cases with CCI mag primers. It routinely (not every now and then) groups them into less than an inch at 100 yards. Awhile ago I threw away my brass. It had been loaded five or six times and since I full length size them, I thought it might be time for some new ones. I loaded up 50 of the same load in once-fired Federal brass. I didnít change anything in the load except the brass. I didnít adjust the dies at all. I used the same powder from the same canister. (New box of bullets though, but the same bullet.)
Yesterday I went shooting with a friend. My first group went over three inches. Iíd given the rifle an extra thorough cleaning, so I thought maybe I just needed to foul the barrel. (Even though Iíd fire-lapped the barrel years ago with that Tubbís kit from Cabelas and the gun usually puts them in the group from a clean barrel.) I let the gun cool and shot another group. Another horrible group. (Plus three.) I then shoot some of the old reloads, with everything the same except the brass. The group was .7. Shoot another group with the new reloads. 2.7. I cleaned the rifle again and tried some of the old loads again. .9. I checked my action screws. All fine. I checked the scope bases. All fine. I shot 25 of the new reloads, and they all grouped horribly.
When I shot the Federal factory loads awhile ago to get the brass, they all grouped about 1.5. I came home and weighed the Fed brass. It averaged 254.5 grains. The Win. Brass was 249. Thatís like 2%, I canít see how that would make that much difference. Besides getting good groups with my old loads, I got great groups with my friends .338 and 270, so I donít think it is my form.
I apologize for being so long winded, but Iím stumped. Do any of you have with more reloading experience have any ideas about what Iím overlooking? I canít see the brass making that big of difference, but donít know what else it could be. My rifle has the BOSS on it. I tried several different settings, and it didnít seem to help. All of the groups with the new loads were really bad. I only have a few of my old loads left, so any help would be greatly appreciated! Thanks.