Need some input.  Just put a new Armaspec Stealth Recoil Spring in my AR10 in 6.5 Creedmoor.  The issue I'm having is it won't lock the bolt back on the final round in the mag.  I have adjusted the gas block from slightly open to fully open and it just won't lock the bolt back.  It will eject a shell and cycle the next round fine.  I can lock it back with the charging handle, so I confirmed it's functioning.  Just annoying.

Have you tried a lighter version?   This may speed up the action a bit but also allow greater travel of the BCG.

Doing some custom grinding of the the weight might let you sneak up on the proper weight for your application.

delete due to my stupidity (failure to read your entire post)

do it single shot and adjust the gas until you get the desired result