IMO: I'd go with this set up, I use it in my ca M15a4, DBC 6.01 barrel (by far the best i'v ever tryed), And kwa 2g bucking.
Can be had for about 100 bucks, My m15 is the m16 style, But it has like 1 foot groupings at 75-85 yards(chronoing at 544-553fps. People up here in washington fear the heck out of this thing. saftey kills at 100feet all day...
People say .01 barrels are to tight. To test this when i installed it i didnt clean it untill it jammed. To this day its never jammed.... About 4 monthes into the test i gave up and cleaned it. This is with gaming every weekend, going thru about 7k rounds a day.
None of the less i was using KSC, JAVALIN, matrix and crossman bb's...Yeah i said it crossman. Precision was sold out..
Heres the links to where you can get this stuff
Barrel:
http://www.precisionairsoft.com/SearchR ... DB+customsHopup bucking:
http://www.airsoftgi.com/product_info.p ... ts_id=5786As for the barrel link i just searched the barrel name, Then you can find the length you want.
Dont forget to lube & wrap the bucking in teflon tape to make sure you get good compression, Also run like 2 wraps around the barrel locker that presses onto the barrel on the front of the hopup unit
Later