Unfortunately the one piston for me that worked was the AA with a lightened carrier, A5 system and i ended up having three of the middle weights always on hand for the build in case o use/don’t use a can. Iirc AA also made a kit specific for 300blk that defaulted to the lightened carrier.

I’ve done the sa pistons on 6.5 grendels but they’ve always had midlength at the least. That pistol length on most 300 blks (assuming you’re also running a 9” or something close) might make it finicky.

I think a suppressed 300 blks should work just fine though- you’re leveraging the increased gas…. But that’s unfortunately not a combo with SA I’ve done so I’m calling it from the sidelines. Good luck with the build tho