300 Blackout Subsonics - for AR15

[Suputin]

With the ludicrous price of heavy .30 cal bullets I decided to work up a subsonic load that will cycle my AR's reliably and still be quiet, while letting me use the less expensive 150r bullets. These two seem to work pretty well in all my 300 BLK configurations. 7" PDW, 10" carbine and 12" rifle. All three of these run pistol length gas systems.

The bullet is a 150r Hornady FMJ-BT for both.

H4198 10.5gr

IMR4227 10.0gr

 

[Paulinski]

I just shoot lead. 200gr and 247gr both with 10.5gr of AA1680

 

[f55]

I shoot these

230gr lee mold, 11.5gr IMR 4198 @1048fps from 9" blk.

If you want to save casting is only way. These cost me around $5 per 100
Both colors shoot same even though red is better coating.

 

[Trinimon]

Thanks for the info. Did you manage to chrony them? Humm, I think I have a bottle of H4198 in the cabinet.

 

[Suputin]

I don't want to get into casting.

I didn't chrony them yet. Weather is still too cold and honestly I don't really care. These are just for cheap blasting ammo.

 

[f55]

Thats fair enough, I was also shooting 150gr hornady as i got 500 free with my press. I usually shoot them super but will give sub a try with imr 4198.

 

[Trinimon]

I don't want to get into casting.

I didn't chrony them yet. Weather is still too cold and honestly I don't really care. These are just for cheap blasting ammo.

So how do you know they're running subsonic and haven't crossed over to be supersonic?

 

[Suputin]

So how do you know they're running subsonic and haven't crossed over to be supersonic?

Due to the distinct lack of a sonic crack. The difference between the two is very obvious.

 

[Juster]

Dear Subsputin,
I just bought a 7.5" 300 Blackout barrel and will try out one of your suggested loads, thanks for the post. Would a linear compensator be a big help, and if so, is there a specific kind to go for?
sjhardware.com has a "Nano Linear comp 7.62" that looked plausible, but what do I know of such things.

 

[Suputin]

Help with what?

 

[Juster]

Help with what?

Ah, help with reliable cycling of subsonic loads in a 7" barrel. That's what I should have said.

 

[Death]

Hey Suputin. Could u PM me interested in chatting about a 300blk ACR

 

[Suputin]

hey suputin. Could u pm me interested in chatting about a 300blk acr

pm cr5.

 

[MikeHudson]

Go with the longer linear comp from S&J
I got both to see which would work with the hornady 208 gr factory loads

 

[Juster]

Go with the longer linear comp from S&J
I got both to see which would work with the hornady 208 gr factory loads

Standard Linear Comp then, that will save me time and trouble, thanks!

 

[Suputin]

Ah, help with reliable cycling of subsonic loads in a 7" barrel. That's what I should have said.

Do a bit of trolling for subsonic loads. Load some up and see if they have a sonic crack and if they cycle. When the answers to those are NO and YES you have a subsonic load that works.