In my limited experience, Spike's overgasses their systems. I only owned 1, and handled a couple others. They ship them with ST buffers (which weight between H1 and H2 buffers), and work well with underpowered Russian ammo. All the ones I've played with, I've been able to put RRA 9mm Buffers into (heavier than a H3) and they cycled under powered Russian ammo without a hitch.. So yeah, Spike's overgasses their systems. This is good because they will cycle just about everything you feed them. But they will beat up your upper receiver parts and BCG and have more felt recoil.
Just the fact that they already ship with a heavy buffer should tell you something......
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