39gr Sierra BK and BL-C2 (AR15)

[coues7]

I've mentioned previously, that I was part of the Specialized Dynamics 204 Ruger Group Buy. I've had the upper for a couple of years now and decided this was the fall to work up loads for it. Shooting factory Hornady 40gn and 32gn ammo I can shoot about 2 MOA....horrible in my opinion for a 204 and horrible for a custom build upper with match grade barrel. With that in mind I set out to load custom loads. I research and came to the conclusion to use 39gn Sierra Blitz Kings and Hodgdon BL-C(2) powder. I loaded up 5 rounds of each load and went to the range. The upper has a 30 cal AAC MK-13SD can on it. Below are my targets:



Any suggestions? The weird thing is that the hotter the load the LOWER it shot. I would have expected it to get higher not LOWER

[TEXAS222]

Hi Coues7. I'm not a gunsmith but have built several custom varmint/target heavy barrel AR's. I had a similar experience with a 204 AR I built with a 1-9 twist Shilen barrel. 1 1/2 to 3 inch groups with factory ammo. Determined to shoot the 39 gr. SBK, I tried 5 different powders, not BL-C 2. To say the least, disgusting. I finally got H4895 to shoot 1" or maybe a little better. 40 grainers were even worst. I was going to send the barrel back to Shilen but I tried some 35 grain Bergers & found a place I could live with, not the 1 hole fly holes I envisioned, but decent. With CFE 223 or H322, I got it shooting around .500, the overall nod going to CFE. I know it's a pain but if you know you have a good barrel & a solid mount system & good shooter control, you might take your barrel off & put it back on torqueing the barrel down to 55 + ft. lbs. up to 85 ft. lbs. Sometimes this will cure an accuracy problem. Hope you get it worked out & let me know. Have a good evening,
Jim D

[coues7]

I'll see what I can do. Taking it apart and re-assembling shouldn't be an issue.

[Darkker]

Have a few ideas for you.
I agree on the reassembly, AR's certainly can be a loveless bride, when things aren't just so.
Next is the bullet. I've had, and known guns that just do not shoot those longer bullets well. Current one will, can't say why, other than the actual twist Vs. Stated argument.

Last is a bit of an unknown. I didn't really catch this, but if you have shot many rounds of a coated extruded powder, specifically Hodgdon's Extreme Series there could be your issue. The issue does show in anything, but extremely quickly in sub 22-cal bores. The coatings create a hard Carbon fouling, without frequent aggressive cleanings you won't even see it; let alone get rid of it. Can be a real maddening affair.