So, my field gun, "Waldo," has another spat of upgrades applied. Sent it to Halycon Defense in TX. Had the barrel cut, the FSP moved back, and a Warcomp pinned/welded in place. Also had a KNS adjustable piston installed while I was at it.
Got it back a few days ago, tested it at the range yesterday. When tuning the KNS piston, I found something unexpected. It wasn't the ammo that was the bigger variable (was using Golden Tiger and Tula 8M3), it was the MAGS used. The KNS manual states to tune the piston with a full magazine, since that's the point at which the bullets pushing up on the bolt carrier exert the most friction.
Polish polymer 30rd mag, unsuppressed, would not cycle properly unless the piston was fully closed.
Hungarian 20rd tanker mag, unsuppressed, I could take the piston out 12 clicks. My assumption is that it's because the 20rd spring is weaker, as it doesn't have as much ammo to push into the gun.
Suppressed, I could add 20 clicks on the piston on top of those base values.
Recoil overall felt pretty mild and not bothersome. I assume that chopping 2" or so off the barrel, but keeping the same gas port etc, means a bit less pressure going into the action.
That was the range testing, anyways. Today I took it out and resanctified it in the mountain snow.
(I normally don't take the obvious glam shots like that, but I wanted to showcase the new upgrades.)