Re: Reloading Techniques
I wouldn't worry too much about the JB, my 300 Ultra (factory barrel too) polished up nicely with many strokes using the stuff, now it copper fouls very little, Flitz works well too. The new Lilja barrel gets the JB treatment just as well.
I hate to suggest a bullet that's even more expensive, and one you probably don't even need, as far as terminal performance, but the Accubond has proven very accurate in two of my rifles, you just might try it and see.
Try the loads with and without the brake on it. The 300wm isn't that much recoil and it may shoot better without it, it will change harmonics.
Size your brass for zero headspace.
Inline or competition sleved type seater will help RO numbers too.
RO numbers may be "high" on "fired" cases, ie. offset chamber neck (like mine, .005" RO) or thin brass on one side of neck. Look at the RO numbers after each step. Rotating 180 deg midway on seating can help, although I think the die setup pretty much determines the outcome no matter what you do here.
I don't use mica, never worked at all for me. I don't clean the powder residue from the necks either, I think it keeps the bullet from bonding to the brass and keeps things more consistant if the ammo sets loaded longer than a few hours. I also don't tumble brass either. They get cleaned off with a damp rag after using water soluble lube, Redding or RCBS, either one, the water soluble type tho. Brass is clean enough for my beauty pagents. [img]images/icons/grin.gif[/img] Necks for factory chambers are nk turned for 80-100% cleanup. Bullets seated on lands, or into lands .010" to start any development. Ladder test to note MV and group nodes at 300 yards or more. Ladder test again to confirm the first one wasn't BS. Clean too often and you'll often deal with powder fouling inconsistancies that screw your tests all up. Often takes three or more to settle in, even when changing bullets or powder... stick with one combo throughout test. Know that these could be affecting groups if switching powder or bullet, best to start clean.
Hard to say what's causing the fliers. If you're using a 210M, try a 215M, or the other way around with what looks like a good load.
Do the groups string vertical, or horizontal.... or just round with a flier?
Only change one component at a time.
You might try H4831 or H4350 too.
I decide on a powder, then find the best bullet, then best OAL, then best primer...