I have an almost complete collection of Gen 1 Ace's, so I'll add some more information. Every Ace that I have is over gassed except for the 13" and 8" 5.45x39's which are perfectly gassed as is. Oddly, my 308Win chambered SBR seems to be under gassed, though it hasn't choked on me yet. So, if you get an Ace, you should pretty much plan on buying a KNS piston. Shoot it first though just to be sure.
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