I inherited a older Remington 721 in 300 H&H and am having some issues with it. I don't have a 300 mag, so I'd love to get this thing running. A range session earlier this week didn't go well. Handloads grouped at 3"+ and old factory Core-lokts actually tumbled and hit the target sideways!
After taking it home I tore it down and had a good look at the barrel. I was surprised to find that bore was incredibly copper fouled. Looked like this thing hadn't been cleaned since it was bought in 1956.
I spent the last three evenings working at it with copper solvent and JB paste and eventually got it down bare steel again. However, I never could get it to the "shiny" stage and it looked just slightly frosted. A followup range session today had it shooting much better. Initial groups were 1.5-2" but they shrank noticeably as I continued to shoot, and by the time I had worked through a box I was getting between 0.7-1.1". All good right?
The problem is that after 30 rounds, I'm seeing significant copper fouling again. Looks like I've got a fairly rough bore. Anybody have any advice on what to do, other than just clean the heck out of it every time I shoot?