I'm planning on picking up one of the piston conversion kits from Adam's Arms soon to build an upper for my Colt Piston Carbine lower and have a couple questions.
Basically the upper will consist of a Colt M4 upper, 16" Colt barrel with carbine gas, Colt 556 bolt, hopefully a Gen 3 Midwest Industries rail and obviously the AA piston kit. The lower will be standard other than a Geissele Super 42 H buffer and spring.
I've read that the gas port may need to be opened up after installing this kit, how common is this? I can do it myself and realize I'll probably just have to test fire the gun to find out for certain. Maybe a standard weight buffer and weaker stock spring is better to start with?
Does the gas block fit under most of the popular handguards people use? I tend to prefer a longer handguard leaving a couple inches of the barrel exposed and would like to run the 12" or 15" Midwest Industries gen 3 mlok rail. They seem to have pretty good clearance although I've only used lo-pro blocks with them.
Lastly, is there a better piston kit I can buy for under $500? I would prefer to just buy the matching Colt 6940P upper but we all know how uncommon and grossly expensive they are so a kit is my only option at this time (I already have a spare stripped upper and bolt so I dont want to buy a complete upper from Adam's Arms or whatever).