300 blk newb need info on light sub sonic loads

[300newb]

I have a new (and my 1st) 300 blackout 10.5" pistol. I was originally just going to use supers in it, then had a thought. Not sure if it can be done but has anyone used 130g projectiles for subsonic? I know it can be done for bolt guns but is there a powder than can be used to generate enough pressure to cycle the action in a 10.5" pistol AND keep it subsonic.

The only reason I am thinking about this is I have a slug press I use for pressing 62.5g 30 caliber slugs for my air rifle. Problem is the max size I can press with this slug press is 130g slugs. If I can find a powder that will cycle the action and keep it sub I have a friend that will coat them for me.

If this isn't doable without changing everything out like lighter buffer and spring, lightweight bcg then I'll just keep shooting supers.

The small slug in the front of the dozen 130g slugs is a 62.5g which I use for the airgun.

 

[dantiff2]

Short answer yes and no… slow burning powder and reduced power buffer springs can be modified to work but it’s a lot of trial and error. Emphasis on error. Once you go down that path, you cannot shoot supers with that same setup.

If you want a direct path then 200+ grain subs are needed without any changeover parts.

 

[Oso]

You need a certain amount of kinetic energy in form of gas volume/pressure cycled back through gas tube to reliably function the BCG on AR15. The 300BO is the smallest cartridge that can operate an AR15 with subsonic loads (subsonic factory ammo uses 195gr-230gr bullet). All of the other subsonic cartridges that fit in the AR15 are larger calibers that utilizing much heavier bullets, such as .338 ARC, .338 Spectre/Razorback, .450 Bushmaster, .458 SOCOM, 50 Beowulf.

I only know of one guy who has successfully gotten an AR15 function with bullets weighing less than 185gr. Your 130gr slugs will not be sufficient to operate the BCG. Sorry.

Good News - I see a single shot CVA in your future for this projectile

 

[dellet]

Suppressed or not?

 

[300newb]

Suppressed or not?

Not atm

 

[SongdogHunter]

With that short barrel is there any reason why not to shoot supers. My 16" supressed with supers shooting110 grain bullets is a lot of fun.

SDH

 

[300newb]

With that short barrel is there any reason why not to shoot supers. My 16" supressed with supers shooting110 grain bullets is a lot of fun.

SDH

All I shoot is supers right now

 

[dellet]

Without a suppressor it will be difficult to get full function without modifications. The there is the problem of the bullet itself. The shape is an unlikely candidate. It’s better to have a lot of room to adjust COL, the nose shape of that bullet looks very limiting.

Around 150 grains it gets a lot easier

 

[300newb]

Without a suppressor it will be difficult to get full function without modifications. The there is the problem of the bullet itself. The shape is an unlikely candidate. It’s better to have a lot of room to adjust COL, the nose shape of that bullet looks very limiting.

Around 150 grains it gets a lot easier

After seeing this 85g by lehigh cycle reliably I think the low pressure will be more of a factor than the shape. Gonna just get a die made for 200g

 

[dellet]

After seeing this 85g by lehigh cycle reliably I think the low pressure will be more of a factor than the shape. Gonna just get a die made for 200g View attachment 1743149

You’re right, can’t imagine what possessed me think that.