if you like quality, this is it. it's ranked in the top2 over at arnies, in terms of quality, next to ipsc. i have one and think it is great. i've had no issues with it jamming, just make sure u get the right barrel spacers. and just order it direct
www.x-fire.org
the6.01 have a new design, i was told that it's 6.01 at the hop, and starts to widen somewhere down the barrel.