Home Forums Hunting & Shooting AR and Tactical Rifles 300 Blackout Short Barrel Sub Sonic Loads

I have a friend that built an AR pistol in 300 Blackout, he is having trouble getting it to feed sub-sonic loads in the 1000-1100 fps range, gun functions flawlessly with regular powered loads. Any suggestions on quick burning powders or possibly changing buffer weights and springs would be greatly appreciated. BTW, barrel length is 7.5"

H110 is the powder to try

Any recommendation of starting grains on a 190-200 grain boolit?

10.9gr of 1680 under a 220 Matchking is a good subsonic load. I have not tried it in a pistol, but in 2 different carbines it ran flawlessly. 1680 apparently generates enough gas volume to reliably cycle the action

I have heard the Lehigh Defense bullets are good on game even at subsonic speeds, but have not yet tried any of them.

does it have an H2 in it, try a carbine first.

The lehigh bullets have been perfect so far this year.

We are having trouble getting pics off my iphone into photobucket for some reason.... the email transfer keeps failing, but I have more pics from this past weekend.

Evidnetly 123 yards is about as far as one wants to go and hit bones.... did a penetration test on a doe, lot of angle, entered behind liver, got liver, lungs, heart and broke off side shoulder at the knuckle joint and thats where the bullet was in the shoulder meat...

I have heard 1680 is the ticket for gas guns. Not sure if that includes shorties.

Feed or cycle, big difference?

AA1680 is what gets my subsonics running a gas gun. 10.5-11 grain range.

Another hoorah for aa 1680 powder. I have a 10.5 inch Noveske upper with an H2 buffer and it has never not fed my subsonics and supersonic reloads and always locks back the bolt after last round fired.

Only thing I've heard is 1680 is not that quiet of a powder even in a can... guess you caon't have it all.

I"m fairly well thinking the port on my Rock tube, will end up being opened until I can get it to cycle with H110 or LIl gun.

In the meantime noise is driving me nuts with my can. Well under supersonic speed, even for the temps, the load I shot friday night should have been sub to -20.. it was probably 65 when I shto it and it was the loudest sub I've heard in a long time.... 2 other hunters about 600 yards away heard it clearly.

Next evening a buddy used same and he was the one that herad my shot, I NEVER heard his, he said it sounded like the normal loud pellet gun...

Who knows...

Not for subs. H110 may or may not work for subsonics, depending on the gun, and isn't the go-to powder by any stretch.

If you're having function issues with subs, start with AA1680 powder; that's what the system was designed for.

If you can get the gun to cycle, Lil'Gun or H110 are a bit quieter; Lil'Gun is the quietest of these three. I found that mine will run subs with Lil'Gun and jacketed bullets as light as 175 grains, but won't cycle cast bullet subs with Lil'Gun or H110 even with 240gr bullets. AA1680 runs great with everything.

For really quiet subs, you have to give up semi-auto function. Any fast pistol powder between Bullseye and Unique works for that, and is a lot quieter, but turns the gun into a straight-pull bolt action.

I still bet that with working on the gas port you can run subs with the quiet powders. Almost has to be. But I've been wrong 3 times in my life... LOL.

Is he running an adjustable gas block?

I'd think that would obviously be the way to run, get an adj block, and then set it basically in the middle, then drill the port until it works...

what do you like best for the 110 supersonics in a 10 inch barrel? Lilgun or H110 or ?

No, was hoping to get it to be able to run both ways without changing anything.

I appreciate all the suggestions, looking to find some AA1680 right now.

No. You'd need an even shorter gas system, and a huge gas port, and probably a lightweight bolt too. Anything that would cycle with the fast pistol powders would have to be limited to those loads exclusively, and couldn't handle supersonics.

You'd have to try those loads to feel the difference. The reason they are quieter is the pressure curve is very short, and the powder/gas volume is much smaller. For example, sub loads with Unique take a bit less than half the powder of comparable AA1680 loads. Bullseye loads use about 1/3 that much.

Both work well, and give top velocities. H110 has more blast and noise, but runs well all the way up to max. Lil'Gun is less blasty, and produces top velocity at lower pressure than H110, but can produce large extreme spreads when pushed too hard.

I prefer Lil'Gun for less blast in the short barrels.

That's how it should be. If the gun "needs" an adjustable block, or different buffer, etc, it's set up wrong.

My Noveske 10.5 inch uses a pistol length gas system, cabine buffer. Cycles and locks back on empty every time. I use H110 for my supersonic and AA 1680 for subsonic. It works flawlessly with or without a suppressor for both supersonic and subsonic reloads. I went with a Noveske Factory rifle as I figured they had already been down the road and found a solution to most cycling issues.