300 Blackout subsonic question

[Crashnrondo]

I just received my 1st can and maybe I'm being a little too cautious but I don't want to have a baffle strike. I'm shooting a 16.5" Encore with a 1-8 twist barrel and a YHM Phantom suppressor, I shot some Remy factory 220gr subs then loaded up some 208gr Amax with IMR 4227. I started at 10.5 grains and worked down to 9.5 grains, 10.5 grains was supersonic, 1 out of 3 would go supersonic at 10 grains, 9.5 and 9.7 both stayed subsonic. My concern is I shot 3 rounds of each after I knew they would stay subsonic but only 2 of each made it on the target and you could tell those went in slightly yawed. My questions, is that normal at 100 yards to have a slight yaw showing up in the target?

 

[Killswitch Engage]

I would not shoot those with your suppressor. They are not stable. You should be getting normal round holes like any other if the bullet is stable. Have you tried trail boss? I am not familiar with that powder but 10gr of trail boss kept the 220 stable for me with 8 tw and subsonic.

 

[rjacobs]

You should NOT have a stability problem shooting either out of an 8 twist barrel.

220g SMK's out of a 10 twist should also be ok. 208 AMAX out of 10 twist wont really be stable, or at least not enough for my comfort.

208g AMAX are almost as long as a 240g SMK if I remember correctly, but still should work ok out of a 8 twist barrel.

Were the 220's going straight through the target or just the 208 AMAX?

Might want to put a rod down your barrel and see what the twist really is.

And trail boss in 300BLK is not a good choice. Its a great sub powder for 308, but not for 300BLK. Fast pistol powders are the go to for 300BLK. A1680, Lil Gun, H110, etc...

 

[Killswitch Engage]

My bad I was thinking of my 308 subs. Yes, I use aa1680 in my blk

 

[Crashnrondo]

Thanks guys, I did check the rifling and it came out right at 1-8. The 220's did punch normal holes, that would probably explain why my 2 groups of 3 shots each I was missing a round in each group. I checked the can and didn't see any strikes but I better take a closer look tonight, and pull about 50 bullets...

 

[Assault116]

Another big +1 for AA1680 for 300blk subs, works great, easy to find that just barely subsonic load, and VERY consistent. Also for those running gas guns it seems to more reliably cycle the action than some other powders used for Subs.

 

[rjacobs]

1680 is the go to powder for 300BLK subs in a gas gun.

However in a bolt or break action like the Encore, there are a ton of powders out there that work well, possibly better than 1680.

To the OP:
I would shoot up what you have without the can and see what results you get. A slight wobble I wouldnt worry about it, sideways I would worry about it. Check em at 25, 50 and 100 yards and see what you get without the can. If they are stable at 25 yards I wouldnt worry about your can personally. Stability of the 208g AMAX out of an 8 twist barrel at 1050 and standard atmosphere(72 degrees, 29.92 pressure) is 1.8 which is damn good. 1.2 is min.