Today was testfire #2 and it didn't go very well. I tapped a screw thru the gas block, to limit pressure, and started with it fully shut. It still cycled, real strong. But soon the cocking plate began hanging up on the cocking tube, when manually cocking. That was the first clue, but I didn't pick up on it. Then I noticed when cocking, it wasn't as smooth, and the rear of the stock seemed to be shifting left. Finally the BC stuck in the aft position, and where the stock joins the rcvr, a gap was opening up on the right side.
It beat the recoil spring gude tube (which is on the right side) against the back-plate, where the stock is attached. Very minor damage (more like evidence) and the rcvr and pin holes are intact. One M11 spring is not strong enough to counter the recoil. There is enough space to locate another recoil spring set-up on the left side, then go from there. Also thinking about a stiff coil-spring buffer behind the bolt stem. There's very little rear surface area for a buffer
I am wondering if a rotating bolt and a super-tight gas system would have been better than straight blowback. I didn't think x25 would have this much energy, while cycling the belt feed mech
On a brighter note, accuracy was good. Was hitting milk jugs @ 150 yards, even though I was distracted with the other problems. I only shot about 30 rds