I have a 7mm RUM that drove me nuts. I bought it used and had no prior knowledge of how it shot.
I tried a bunch of different powders and bullets. Eventually tried a box of factory ammo to see how it would shoot. Even the factory stuff was terrible.
The barrel fouled really bad as well. From a perfectly clean barrel, 3-5 shots down the tube and it would take a whole night of cleaning.
After a few nights of lapping the bore with JB Bore, I sealed everything up with Ultra Bore Coating and the rifle started to behave.
It wasn't much after that when I could consistently put 3 shots into a dime sized hole at 200 yards.
