300BLK Ammo + Buffer Combos

AR/M4 Beyond 5.56/.223
1

I am running a 9inch Ballistic Advantage Modern Pistol Length BBL both suppressed and unsuppressed. I am trying to play with spring/buffer/ammo combos to get the widest range of ammo to work.
My default setup is a ST-T1 buffer with SpringCo White spring.
UnSuppressed it ran 108gr Hornady and 123gr Magtech Supers no issue. 220gr Rem shot fine but didnt locked back on last round. 208gr Hornady didnt feed well nor lock back.
Suppressed it ran the 108gr and 123gr supers no issue, as well as the 220gr no issue. The 208gr didnt lock back.

I switched to a ST-T3 buffer and it was the same results except the 208gr shot better but still didnt lock back.

I also have a Red Spring (dont think that makes sense) and a ST-T2 buffer on hand. I also am considering a white-hot spring.

Any other thoughts on what to adjust or try? Ideally I would like to find at least one sub that has no issues suppressed or unsuppressed and can handle a super on that same setup.

2

I run a Springco yellow & std. buffer in my 8” .300bo pistol with a lightweight carrier, then swap to a std. spring and H2 buffer for supers, but I don’t run a suppressor. I could get away with a std. buffer both ways but the H2 was a spare and I like the feel of the extra weight with supers. I’ve messed with buffer weights and springs in other calibers and found spring rates will make much more dramatic changes in cycling than buffer weight.

3

Mines tuned to a single load; 110 gr Barnes Blacktip at 2400 FPS, 16” barrel, no suppressor. M
Running Geissle 42 spring and H3 buffer.

4

Any idea what the gas port size is?

IMO, subs unsuppressed don’t make any sense, so that combo should be eliminated.

In general, subs should use a light buffer and spring combo, as they are pretty low powered.

Supers can then use a heavier spring and buffer to deal with the extra gas drive.

5

Mine was built as a pistol…standard pistol buffer and spring. Handled sub and supersonic with a can no problems.

6

Start with a standard carbine spring and an H2 buffer.

7

I just don’t think you should need some exotic combination to make this work. While it would be nice to have subs work unsuppressed, that is low yield considering their usage.

Mine has 16" Noveske pistol gas barrel, and it runs everything, in every combination, with a standard CAR spring and buffer. I have tried a H and H2 buffer with no difference noted.

Despite running supers with the can (the most overgassed theoretically!), I have had ZERO reliability issues or excessive gas to the face.

I vote for standard components to start.

8

I have a 9" Suppressed with Adj. Gas >>> A5 - 3 w/ Sprinco Green.

It ran Super and 200g Subs until things got really dirty and the Subs stopped cycling. All I had to do was adjust the gas to get both to work. Waiting on parts but have the A5-2 buffer and same spring on the way if it ever arrives. Really soft shooting. I haven’t tried to fine tune anything so it’s certainly possible with standard middle of the road parts. I think the super was 144g btw.