^ Yes, I would ask that guy about the gen 2 barrel in the gen 1 receiver. There has to be some modification to make it work and I wonder how he went about it, who did it?
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I wouldn’t sweat that so much. The different generations were just a widening of the feedramp. I’d be more concerned if he did any trigger work how he removed the welded trigger pack screw, and when he disassembled the clamshell frame did he strip any heads, did he clean threads and loctite, then most importantly did he reinstall to proper torque spec.
those are the failures I have seen on DIY scorpion Evo HBI upgrades