Quote Originally Posted by Slowpoke Slim
Not sure what powders you have on hand to try?
I HAVE ABOUT ANY POWDER THAT IS MOSTLY USED

Medium to medium slow powders should do it, I would think. I don't load that cartridge myself, so I can't give you my recipe. I would think something like 4350, w-760, 4064, RL-15 area should work.

Before you gave up on H4831, what primers did you try, and did you try several primers in that powder before you gave up on it? Also, did you try different seating depth's in your test loads? My 6.5x284 wants that powder with a Fed match primer. My 243 doesn't like 4831 at all, but loves W-760 and that same Fed match primer.
I TRIED CCI & FED 210 I TRIED & SEATING DEPTH FROM MAX MAGIZINE LENGTH TO 1/8 SHORTER

And you never know when you get that one barrel that just flat will not shoot a specific bullet, or even bullet weight, at all. Not sure if you're there yet on yours, as you have a host of combinations yet to try.

Also try the Sierra 100 gr pro hunter, Nosler 95 ballistic tip, and Hornady 100 gr interlock.
IT SHOOTS THE NOSLERS & HORNADY'S FINE

What rifling twist rate do you have, what is the intended target, and at what distances?
1 IN 10
I HAVE TALKED TO OTHER MEN AND THEY AGREE CORE-LOKT'S ARE JUST JUNK.

--EDIT--

After looking at your load and perusing a couple of manuals, I think you may have to go even slower on your powder charge. Like 7828, Retumbo, H1000, RL-19 or RL-22. Maybe even RL-25, but would probably need a magnum primer for that one. I would not expect to see anything good accuracy wise until you get up near max pressure with these slower powders. That will bring the combustion consistency up where it needs to be and drop your extreme spreads. That is an awful lot of cartridge case capacity for a 6mm.