Thanks! Reading these threads fixed my issue

[c3k]

External piston systems normally are mated with unusually heavy buffers because the gas acting on the piston cup or head causes instantaneous carrier inertia, which is bad for extraction so close to obturation.

Every company that has seriously tackled the external op-rod guns has used very heavy buffers to act as a rate reducer, and they are usually combined with heavier action/recoil springs.

That was EXACTLY what I meant to say.

In a serious vein, I've followed a LOT of what you've written. I'd like to say "thank you" for sharing some of your incredible depth of knowledge. I've gained a lot from it.

Thanks,

Ken