I don't know if I have the best 300 RUM or what but I have shot well over 1500 rounds and don't have a problem. I moly coat all my bullets and shoot Swift, Gland Slams, Hornady, even Barnes and it still shoot an 1" or less group.

Marty, I believe the moly has alot to do with it. I hope you have been recording throat errosion over time. I mean I hear people say moly helps, then others that say no. But I have yet to see too many people really record the errosion.

I appreciate all of the good information that members have sent. Even though I have been hunting and caring for rifles for over 50 years, the Magnum arena is realively new for me. Thus far, I have ordered some Barnes Triple X to try, for as previously reported, the Bear Claw and Grand Slam, both in 180gr, did not produce acceptable groups on a consistant basis. I did use Birchwood Casey "Bore Scrubber" on the bore. That product promises to remove copper build up, but I could barely detect a slight amount of green on the first patch and after that, saw none. I allowed the rifle to sit several minutes between swabbing and each patch came out clean. Therefore, I am ruling out copper build up. No?
I also need to get some RL25 and IMR7828 to test, as the MagPro does'nt seem to do well, even with much reduced loads, but I will try MagPro with the Barnes Triple X. When I phoned the local propellent supplier, from whom I got the MagPro, he claimed that there have been problems of consistancy with both RL25 and IMR7828. I am skeptical enough to believe that he simply does not stock either propellent and is still pushing MagPro.
The men who sit around chatting at Seitzland Rifle Club in New Freedom Pa are getting tired of my flailing away with the 300RUM each Tues and Thurs, but I will not again go hunting with the rifle unless I am confident that I can kill that at which I aim! <8^)
Any other suggestions are appreciated.

I have had consistency trouble out of RL25. I had this great load for 180gr Triple X and then ran out of powder. New 1lb got different results. I had to bump the load up to get same velocities. The temps and all were about the same. Who know.

4350, 7878, H1000, Retumbo, RL22, and AA3100 will all be good choices.

So do many other products but few actually remove copper at an acceptable rate.Many require overnight soakings to remove all copper from a barrel.Sweets and cr-10 remove copper very quickly.

stubble is right, after shooting TBBC, if your barrel is like mine, its going to have alot of copper. Try some sweets, and use as directed.

Thanks Stubblejumper. I ordered some CR10 from Jerry's Sports Center. Should receive same in next week's order. I used both the "GunScrubber", that I mentioned and Hoppes "Bench Rest". Neither pulled out any more green on the patch, after being left overnight. I will see if CR10 gets any more out.

Steven, if you need any advise, I only live 5miles from ya on Ridge Road. I suppose you go to the Happ Baker range, like myself.

I can't promise any words of wisdom, but could tell ya what does and does not work for me.

Barnes CR-10 works well for me also and seems to be a quick, aggressive solvent. But when I want an absolutely clean bore I plug in my Outers Foul-Out electrochemical system. Time saver, possible wear or damage from cleaning rod saver, and odor free. Clean a rifle conventionally then use the Foul-Out on it and see what was missed. Works even better with lead. It is also the only lead remover I use nowadays.

I would love to try this thing "outers" out before buying.