I'm looking to play around with 300blk in an AR but I can't find any of the preferred powders for it.  Mainly just looking to load supers and not subs.

I have some old HS-7 powder sitting around and I'm wondering if it would work for 300blk loads?  I'm just wanting to load cheap plinking rounds, so it doesn't have to be optimal but I don't know enough to know if it would even be safe to try.  I've seen some people using Blue Dot and the HS-7 has a similar burn rate.  I was thinking maybe the HS-7 would be workable with lighter projectiles, say under 150gr?

I believe HS-7 and Longshot are similiar.

Too fast for the 300 BLK in an autoloader I'd imagine.

Would work well in a bolt action or a Handi Rifle though.