+1 on this but I'd go with green 620 loctite for the barrel extension....at least that's what the Criterion guys use when building precision AR-15 uppers.Aero Precision matched upper and lower. Convert to side charging. Kreiger or Bartlien barrel. Whatever weight and length you want. Magpul fixed buttstock. Tigger Tech or Timney trigger. clamp on gas block Non adjustable. Blue lock tite for barrel extention into upper receiver.
Find ammo that gun likes! Go have fun with it!
Also have front of upper receiver lapped square before putting on barrel
See here for their steps to assemble a precision AR-15 upper:
- First lap the end of a BCM upper receiver (or similar quality upper receiver)
- Heat end of upper receiver to open it up if needed
- Spread green loctite on the base of barrel extension then slide it onto upper receiver
- Apply anti seize grease to barrel nut threads and shoulder contact points, thread on barrel nut while upper is still warm (once cool torque nut to ~40 ft-lbs 3 times then leave it on the 4th
- Re: the materials of certain parts, use a raw stainless steel gas tube ($16) (for more flexibility only use raw stainless steel non nitrided gas tubes), steel barrel nut ($9), and badger ordinance TDX steel gas block (use steel barrel nut, gas tube, and gas block to keep all materials the same as the barrel)
- Pin gas tube to gas block and to install the block use a tiny amount of rocksett (or high temp blue loctite 246 thread locker) on gas block set screws only snug tightened (20-30 in-lbs). Make sure the gas tube doesn't have any tension on it and has a little "wiggle" (see above video for details).
- To install muzzle device that will be used as a suppressor mount, use rocksett or blue loctite 246 and alignment rods for installation (make sure to degrease any screws or threads where threadlocker will be applied) then torque down to no more than 20 ft-lbs. If installing a muzzle device that won't be used as a suppressor mount you can apply a little grease to the threads and simply hand tighten it (similar to how bench rest shooters install muzzle breaks).
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