Impossible 300 Blackout accuracy issues

[popper]

Didn't say what sights you used. 1:7 is OK but 1680 doesn't burn right/complete in the barrel. Plus it' a AR pistol! 2400 should work better. The Lee doesn't get any rave reviews. Might stay with COWW. PC & WD@309. IMHO you're doing fine 3"@100. Might try single loaded not from mag to see if nose gets 'bent'.

[Burnt Fingers]

Didn't say what sights you used. 1:7 is OK but 1680 doesn't burn right/complete in the barrel. Plus it' a AR pistol! 2400 should work better. The Lee doesn't get any rave reviews. Might stay with COWW. PC & WD@309. IMHO you're doing fine 3"@100. Might try single loaded not from mag to see if nose gets 'bent'.

So if I'm loading 9mm for a 9mm RIFLE I should use rifle powders??

[Wisest.fool]

I am no OP but now that i have seen all these suggestions i am gonna try a few in my 16" cmmg upper.

Gas checks i havent tried.

Seating depth i havent tried. I just made sure they would fit in the magazines.

And im using imr 4227 and lil gun if i get better results i will post it here.

[sigep1764]

So if I'm loading 9mm for a 9mm RIFLE I should use rifle powders??

Burnt, I believe Popper was referring to 1680 not being able to generate a complete burn of the powder load because the barrel is short. I also believe he was referring to the Pistol Length gas system needing a lot of gas fast and that 2400 could achieve this. I do not think it was a matter of the specific cartridge in a rifle or pistol.

[sutherpride59]

Boy howdy when you find the secret to really accurate subsonic 300 AAC loads let me know lol. I’ve only don’t a tad better than you with my 16” barrel. Gas checking eliminates the lead fouling in my suppressor but doesn’t do anything for accuracy IN MY GUN so I always use them. As others stated seating depth is a thing. I have had issues with large velocity spreads in mine using H110 or 300CFE. I ladder tested some with W231 just to see how quiet they would be and when I have some time I’ll test them for accuracy too. Just need to have that “free-time” I keep hearing about lol.

[popper]

2400 will give good burn in 7". Tried cfe p, 1680, 2400 in my pistol, 2400 worked best and would cycle, 170gr PB. I assume a scope was used for 100, but real problem is a pistol is really hard to shoot 100 for testing as a stable shooting platform is hard to make. I've read about 44mag pistols hitting hogs in the shoulder @ 80 yrds free hand - maybe but not me. 3x scope@ 50 with bipod - 2400 does cycle, this is ~1k fps. I would need a 9x scope for 100. Add an extra ~7" drop @ 100 for this load, energy is only 330 ft-# terminal and 440 ft-# for 240gr. Not even legal for deer hunting in some states. IMHO the OP goal is on the ragged edge.

[300blak]

That’s correct on using a scope. Vortex Strike Eagle 3-9x40. I’m shooting it prone with a rest to eliminate as much error as possible. If I can scrounge some 110 or 2400 I’ll give it a shot as well. Trust me. If anything works, I’ll post it here. I use Gordon’s Reloading Tool and that is a correct statement that the 1680 is not a consistent burn. From my specific data, it’s only showing a 74% burn rate.

[Lloyd Smale]

like larry said use a hornady or gator check they stay on and get the soft lead is better idea out of your head. If all you have is ww then water drop it. With pc its easy. Just take your bullets out of the oven and dump them in cold water. A 1-7 twist is to fast for soft bullets. they are probably stripping through the rifling. I agree with yovinny to a point too. Sub sonic loads arent meant to shoot at a 100 yards. There mostly up close and personal sneak in shoot and sneak out rounds. That said i do have a sub sonic load that shoots but its no good in an AR. My ruger american with a can on it shoots the 130 rcbs spitzer gas check bullet with 4 grains of unique into under 2 inches at a 100 yards. Trajectory is like a rainbow though but its pretty cool as its no louder then a pellet rifle. Much less noise then the bolt slamming back and the springs compressing and slaming it back in an ar and quieter even then the sub sonic 200 plus loads with powders like cfe blk and 1680.

[popper]

300blk - thinking maybe powder burn in the can may lead to loss. Post targets pic we might be able to determine what is going on, horiz/vert stringing, shotgun, etc. I use GRT too. I use a bipod for testing but your short barrel doesn't have much to hang on to, I get a little jump from my 10", mostly bolt movement and torque reaction from spin.
power pistol or accurate #7 might work also. H110 I don't download!