my first custom gun is coming together and I'll be doing load development soon. With a 1-8 twist i thought the Sierra 107 MK would be a good place to start. Not too sure though about the powder selection. I'll probably need a fairly slow powder to get the most out of the 30" barrel. IMR 4831, RE22, and VV 160 or 560. Thought I would start around 54 gr. and work up. Anyone have more specifif loads that they have tried that gave the best accuracy. Thanks in advance.

With the 107 Sierra:

IMR-4350 From 41.7 grains to 49.3 grains
Winchester WLR Primer

Carverelli,

Sounds like you just discribed my custom 6mm-284. I built mine on a Wim M70 Short action with a stainless, fluted, 30" Lilja barrel with a 1-8" twist.

I really have only played with one powder, RL-22.

I started with this powder and the 107gr MK's that you list. Once the barrel was broken in I moly coated the 107's and started with 52.0gr Rl-22 lit with a CCI-BR2 primer. My first group at 100 yards went into 3/8". anything under an inch at 100 yards with these very long bullets will look real good at long range.

I did stay at 100 yards for the velocity testing and reached a max of 56.0gr which gave an average velocity of 3595 fps for ten rounds with an extreme spread of 16 fps.

This is a hot load, in fact it may be a bit to hot but it shoots like wildfire and the way I use this rifle, 800-1200 yard rockchuck hunting, even this hot load will last a very long time.

As far as long range accuracy goes, I set up at my 500 yard range to get the scope set up for the chuck season last spring. It took five, three shot groups to get the rifle printing where it should for a 850 yard zero.

Of those five groups, all were under 2", and two measured under an inch.

I have shot this rifle next to other shooters shooting the 30-378 WBY(180gr Bal. Tip@3500 fps) and 338 Lapua(250gr@3050fps) and my little 6mm bucked the wind and shot flatter then both, much flatter then the 338. On target performance is of course less dramatic but so is the recoil and muzzle blast.

Try Rl-22, start at around 51.0-52.0gr and work up, hope it works as well for you as it did me.

Good Shooting!!!

50

fifty, thanks again. I hope to get my gun back from Dennis soon. I'll start loadin around 52 grains and work up w/ RL22. I'm sure it'll shoot great. Had Dennis make a brake for it also. maybe that's what taking him longer tyhan he thought.