Re: Real Poor Shooter w/factory ammo, how much can I really expect?
If you check the web sites of some of the custom barrel makers, those that recommend twist rates for bullet weights recommend a 1 in 8 for bullets above 140g. (I'm thinking Shilens' web site). Seems there's a discrepancy, sometimes, between what bullet makers and barrel makers recommend. I'd try some bullets weighing 140g. and less and see what happens. I'd make sure I didn't have that copper fouling, too. I see many barrels the owner says are 'shot out' and when I run a strong copper solvent thru them until the patches come out clean they go back to shooting. Ammonia based copper solvents will turn copper the color blue, so it's easy to tell when all or most of the copper has been removed. You may need to find a 'smith that has a bore scope for a good look-see. I have, also, seen dramatic changes by changing propellants or primers. Just because some say this is the best for that cartridge or load doesn't make it so. Every barrel is an individual and should be treated as such. Sounds to me, though, either the barrel is badly fouled or worn out, or you are shooting the wrong weight bullet. Any of those will make for a rifle that shoots 'patterns' instead of 'groups'. From this distance, all I can do is speculate.
"Shoots real good!": definition; it didn't blow-up in my face. 1993 graduate Montgomery Community College 2yr. gunsmithing program