Dpms sass g2 gas piston conversion

That's probably the worst thing you could do to that rifle if it were possible. Adams Arms has external piston uppers for the GII, but I would never do it.

Why do you say that? Will the weight of the moving parts degrade accuracy? The only reason I posted this is because I would like to keep the chamber as clean as possible.
 
Terrible idea, you are paying a lot more for decreased performance. Just get a superlative arms adjustable gas block and you will be gtg.