Well, I've had the MB06 for several months, and recently, I've been noticing a stiffer bolt pull. I've torn it down completely, and can't find the problem. The entire cylinder will slide smoothly in the outer barrel, and slide smoothly in the upper receiver, but when I put the outer barrel into the upper receiver, the cylinder slides with a lot more friction. This is making my bolt pull much stiffer. Anybody have suggestions on how to fix this? I haven't gotten around to putting in upgrades, so it is still completely stock.