300 blk subsonic loads for pistols

[NCHillbilly]

Does anyone have load info or insights for loading subsonic loads for an ar pistol. 8.5 inch barrel, 1-8 twist. I have some hornady 208gr bthp's and 220 smk's I'd like to play with. I don't currently have a can for this weapon, but that will come later. I have rifle data, but don't really know where to begin with the pistol loads, other than to start at the top of the chart and work backwards CAREFULLY.

 

[101stinfantry]

I haven't loaded any yet, from what I remember from my Hornady book was Accurate 1680 worked best for keeping loads subsonic and still cycling the action on an AR-15.

 

[NCHillbilly]

Yeah, I've got their manual too, and I remember seeing AA1680. I just wasn't sure if loads tested in a 16" barrel with a carbine length gas system would function properly in my pistol set-up. I'm looking forward to playing with this thing, and I have a few powders that are listed in the manual. I just don't want to have to beat a stuck bullet out of the barrel, or inadvertently disassemble the weapon upon firing. LOL

 

[101stinfantry]

Well, your going to want to stick to around 1,040-1,060fps to keep them subsonic, so that would give you a basic idea. I also, don't think that going from an 8.5" to 16" barrel is going to put on a ton of velocity with the heavies. I've just been shooting the S&B, and Remington factory subs so far, while I build up brass. I have an 8.5" AR SBR, and a 16" Howa bolt gun.

 

[spife7980]

Cfeblk. It’s literally in the name lol

 

[NCHillbilly]

I built the pistol from a kit, and it has a non-adjustable gas block. Should I change it to an adjustable, or just load it up, run it, and see what happens?

 

[R0CKNR0LLKL0WN]

I’ve been running the 220 SMKs from my 300 BLK SBR for a while now. Using 9.8 gr of IMR 4227 gets me a MV of about 1050 from a 10” barrel. I have an adjustable gas block on mine, but I’m thinking you may be ok with a pistol length gas system. Meters nice, no malfunctions, and no unburnt powder or anything like that. I’ve also only ran it suppressed. Your results may vary.

 

[odoylerules]

8.9 gr of Lil gun in my pistol with 8.5” barrel pushing 200 gr pills. Runs perfect

 

[bmash]

1680 powder (didn’t have the new cfe when I did this)
208 A max
11gr: 8.5” 963 - 1044fps; 16” 1089 - 1112fps
10.6gr: 8.5” 897 - 943fps; 16” 1057 - 1061fps
10.2gr: 8.5” 875 - 940fps; 16” 920 - 971fps

wide range of velocity, huh?
10.5gr would cycle both guns, but the lower you go the quieter.
i just load and as I remember most loads would cycle since bullets are so heavy And I was using a suppressor...
be SURE they are stable before using a suppressor.
Oehler chronograph - you may need a blast shield (cardboard with a cut out you shoot through) to get a reading with subsonic. The blast sets it off before bullet makes it read...

 

[NCHillbilly]

Thanks for the help. This will give me somewhere to start. I have some of the powders you fellas suggested, and I'll pick up some others. I've been looking forward to lighting this thing off for a while. Nothing like load development for a new rig.

 

[DAMNKID]

I’m using 10gr A1680 under 240 lead cast avg vel 1040 with a 9” Kak. bolt holds open on last round and using a non adj gas block with no problems. I would start alittle above 11gr and work your way down there if using this powder.

 

[Dill]

Don’t fret if the gun doesn’t cycle or lock the bolt open without the can. Once you add it, you’ll get a lot more gas and stuff will work better.