Took my Rem 700 (257 Wby, 26", 1:10" twist OEM bbl) to the range today to shoot a load workup with a new powder and a couple bullets.

I had loaded both 110 grain Accubond and 115 grain Ballistic Tip (coyote exploder) bullets, using Hodgdon Retumbo powder. The workup was from 65.0 grains to 70.0 grains in 1/2 grain increments using Federal 215 primers. Bullets were seated to a COL of 3.17" (the recommended seating depth and SAMMI Max COL). At 70.0 grains there were no pressure signs at all.

Accuracy was atrocious. The best "group" was 3 of 5 shots into about 1.5" at 100 yards... the other 2 rounds from the group were way out of the group by almost 4". I did notice some tendency toward vertical stringing, but many of the flyers were just randomly all over the paper, with the "groups" being 6-8" at 100 yards. The only good news was than all shots landed on the 8.5x11" target, some just barely. The really strange thing is that this same rifle had been shooting 1/2 MOA groups the last time out with a different load (the powder for which I can't get because everyone's out of stock).

The prior load was with Barnes T-TSX bullets (which shot sub-MOA with the best groups sub 1/2 MOA), so I decided on a hunch to try some copper solvent (Shooters Choice) when I go home, and I'm getting what seems to be a LOT of copper out. I send a patch wetted with SC copper remover through, wait 5 minutes, and then dry patch until no more blue comes out. I've repeated this process at least 10 time (I've lost count), and I'm still getting some blue on the patches. Not nearly as much as the first few times, but it's still a noticeable amount. I'm wondering if this could possibly be the culprit behind the bad accuracy, or if I should be looking for other stuff, too. The temps were a lot cooler than the last time I shot it, and I waited at least a minute between shots and roughly 5 minutes between groups. My rule of thumb is that if I can't hold my fingers on the barrel just ahead of the chamber area for a 10 count, then the barrel is too hot to shoot.

I'm getting tempted to take the JB Bore Compound to the bore and lap it down to bare stainless and start over, but I don't want to mess up this barrel. I'm also wondering if it might be a bedding/pressure point issue, since the laminate wood stock has the typical Remington factory fore end pressure point on the barrel.

Thanks for your input.

Mike