Quote:
Originally Posted by marathonrunner
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He said if you were to build this using the conventional means, "home methods" that there is a chance I may or may not get the indexing right on the first try, and that you can only loosen and re-tighten the threads on the receiver before they become basically no good.
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That's not the case. I've got a half dozen barrel changes on my Service Rifle AR-15 and there's no reason it can't go a dozen more.
You do want to at least lightly lubricate the threads, to reduce the potential for galling the aluminum and keep the anodizing intact on the receiver and the 30 to 80 ft pound torque values are based on lightly lubricated as opposed to dry threads.
Here are the torque specs that matter:
Compensator (Flash hider) 15-20 Ft. Lbs.
Barrel Nut - 30 Ft. lbs. Minimum, not to exceed 80 Ft. Lbs. to align the next slot in the barrel nut.
Carrier Key Screws - 35-40 INCH pounds.
Lower Receiver Extension (Buffer Tube)
Rifle: 35-39 Ft. Lbs.
Carbine: Tighten the castle nut to 40 INCH pounds +/- 2 inch pounds.
Bear in mind when torquing the barrel nut that the barrel nut wreck is in effect a crows foot, and the offset on it will affect the torque value. It's not a big issue unless you are close to the upper or lower limits.
Figuring torque with a crows foot wrench
Headspace should not be an issue with barrel extension and bolt that are within specification, but you do want to check it:
Head space information FOR 5.56
New barrel Headspace: GO gauge 1.4636
NO GO guage 1.4696
Field/Unsafe barrel Headspace: 1.4730-1.4736"