Good morning! Working on a subsonic 300 BLK dope for my suppressed SIG Sauer Rattler. My first batch is:

200gr Hornady ELD-X
Hodgdon H110 = 9.2gr
COLA = 2.250"
Remington 6 1/2 primer
Brass = Lake City (new)

Great sound signature suppressed and accurate. But getting FTF regularly. This dope worked fine on unsuppressed 16" barrel ARs. Has anyone worked up recipes for 8" suppressed AR pistols with 200-208gr bullets using H110.

Thanks!

Watch your case capacity with that powder,and use mag primers.
That h110 need near full to be safe

The only powder I found to work on 208gr and 220gr bullets both suppressed and unsuppressed was A1680 powder. Other powders would fail to fully cycle the bolt. My gun is a 10” barrel and I haven’t tried loading a 200gr bullet. I would look at A1680 for your powder when trying to do subsonic suppressed.

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Exactly what Stormin Normin posted. I have loaded and shot thousands of 190gr thru 220gr rounds of 300 AAC B/O Sub-Sonic rounds (suppressed and non-suppressed) thru my 4 different rifles (one Bolt and three AR’s - two are registered SBR’s - 8” and 11”) and 1680 cycles consistently in all rifles.

Try some IMR 4227. Works great suppressed and unsuppressed in my 8.3” 300blk and Ruger American Ranch 300blk.

looking at Hodgdon data your 9.2 grain load is perfect. Based on developed pressure I'm thinking that CFE BLK may be the best "fit" for this application. That low developed pressure indicates to me that the pressure event occurs over a longer period of TIME and that should provide a longer pressure event driving the bolt for a move complete cycle. BTW, I have an adjustable gas block on my 300 BLK specifically to permit tuning the gas system for the specific purpose that it's being used for. Downside is that adjustable gas blocks do require regular cleaning or they'll get clogged up and become a major headache.

I’ve had no issues using CFEBLK for 200~220 gr bullets. I use H110 for lighter weight supers.