About ready to throw in the towel
 

Hello I have a new build with under 500 rounds
AR 15 300 Whisper Matchgrade Upper - Barrel length 10" 1:8 twist
AAC Cyclone Suppressor
RRA Lower Receiver Lar-15
20 Rd P Mags
Load:
9.1 H110
220 SMKHP
COAL 2.235
Gas block set for subsonic
After weeks of trying different powders, bullets, and brass, I have not come any closer to getting decent groups than when I started.
Shooting outside in decent weather(50degrees)with just about no wind.
Stable bench and bags
Scope,rings,and base are tight.
Suppressor is tight.
Triiger is 2-3 lbs
Do not want to mention the builder nor do I want to say any negative but they have been little to no help at all.
Looking for recomendation for a knowledgable 300 Whisper/gunsmith that I can send this off to.

I am shooting a bolt gun, had several decent 5/8 or 3/4 inch 4 shot groups with a couple diff powders.... Figured I'd tweak the load and seat bullets out just shy of the lands MIsTAKE = they opened up to 3 and 4 inches,,,, seated bullets back in (240SMK) at 2.195" groups shrunk back 5/8".
I beleive that it has to do with the voulme of the case,, the load is closer to 80 op 90 percent full at that length. Fwiw am using 9.5 gr of 296, 4227 works good, just using up some of this old stuff.
Give it a try nothing to loose
Jim

sorry to hear about your trouble, I feel your pain , getting my AR whisper running smooth and accurate took some real effort. I lightened my buffer to 1100 gr and opened my port to .116" but I now dont change anything from Subs to supersonic rounds..Your grouping problem Might be the powder. I had much better sucsess with 4227 and 1680. what twist is you barrel?

Ok I just saw 1x8" sorry

where are you?

Have you put any of this ammo over a chrono?

Yea, with only 9.1gr you could be in the 800fps range--these guns really vary in subsonic performance. Chrono the load and get to 1000-1050 fps and check your accuracy. I really like AA1680 powder personally.

Any updates? I hate to see a grown man cry.