[Hectic]

pss10 ftw, teflon cylender, air seal chamber, 6.02 or 6.01 tightbore, pss10 piston, reinforced first and seccond sears, then just chose a spring to suit your fps needs. Cut a peice of o ring or the clear plastic bit of a pen and put it between the nubs on the hop up arm for better hop up for heavyer bb's i run .36's but thats a 513fps gun, id say .30 would be good for 400ish, tho not sure y youd want 400 most places allow 450 even for new snipers.
all told you will probably spend 3-500 on parts to build a consistant platform but with a clone(i use a TSD) it will still have issues, im just waitin to find a mauri to swap my parts into.
Good luck, enjoy.