I've been reloading now for 15 years and have never run into this problem, I've checked the forums on several different sites and decided to post on this one. I purchased a 300 RUM Sendero in August of this year. (First mag I have ever owned or reloaded for) worked some loads up that the gun liked. Rem Brass- Fed GM215M primer, IMR-4350, 80.5 grs, sitting under a 180 gr Accubond. The powder vol. is only about 84 or 85% of the case capacity which is less then I like vol. wise. I loaded up 15 more for hunting season in October, same load and decided I would shoot them. Prior to shooting them I ran across a loading manual that listed the max powder load for the 4350 at 80 grains. I've been using the Nosler 6th addition for my cookbook and they listed the max load of 4350 at 82 grs. I had some concerns however since I had already been using 80.5 grs with no problems , I sent them down range through the chron. and the velocity was within 9 fps of book values with the exception of the last shot which spiked about 40 fps. On the last shot the bolt stuck a little and I assumed that I had heated her up a bit as there was not any downtime cooling off period for the last 3 shoots. After inspecting the brass at home I noticed that all 15 casings had the primer backed out a thousand or two. These cases had been fired once before and this was their second outing, trimmed to 2.840 and neck sized only. Bullet seating same as before. Anybody got any opinions, I've seen a few, indicating primer pocket problems, a few indicating low pressure, and head space problems. In light of that other reloading manual that listed the max load at 80 grs I'm sort of at ground zero. I was getting to ready to work another winter load up with this powder and jump it a little closer, Its had 65 rounds fired through her from day 1 total. I've got some RL 25 and some magnum powder that would fill the case I just don't like taking more pounding then I have to. I'am not concerned with the fraction of a second or a 100 fps slower vel. The deer nor the paper could ever tell the difference and I have plenty of vert adjustment left in the scope to fix that. Anybody got any opinions or loads they would like to share it would be nice, I have no problems using another powder or bullet for that matter.