12-23-2011, 11:06 PM
Get a lapping tool and lap the upper to square the face where the barrel extension goes with the axis of the bolt carrier bore. Lap until all the black is gone and there's a light, dull-grey surface (aluminum) for the barrel extension to bear against.
Follow terrywick4's advise and torque it twice with some kind of lube to prevent galling the threads (I use anti-seize).
On final installation of the barrel (second torque), goop some loc-tite on the barrel extension to fill in any voids or gaps between it and the upper. I like the blue (removable) stuff.
I'd look up what people are using for torque spec's on the barrel nut. Seems some folks are backing away from the "go to 60 lb-ft and then go till you align the next hole for the gas tube" - particularly with the precision uppers. That said, I think I remember torquing my last .223 build to 60 lb-ft and then lining up the next hole. It shot well, but it didn't meet my 0.5 MOA standards. Barrel wasn't "match grade" anyway.
I wish I could remember what torque we used to install the White Oak 24 in Match barrel in a friend's upper -- that shoots one-hole at 100 yds with 60gr Vmax's.
Lapping is messy. Make sure you clean every last bit of grit or it will affect your torque readings.
After barrel assembly, the next trick is to use a clamp-on gas block. After that, it is aligning the gas tube with the bolt carrier key. After that, well, everybody has tricks they prefer but I can't prove any of mine make a significant difference on the target.
Hope this helps.
Follow terrywick4's advise and torque it twice with some kind of lube to prevent galling the threads (I use anti-seize).
On final installation of the barrel (second torque), goop some loc-tite on the barrel extension to fill in any voids or gaps between it and the upper. I like the blue (removable) stuff.
I'd look up what people are using for torque spec's on the barrel nut. Seems some folks are backing away from the "go to 60 lb-ft and then go till you align the next hole for the gas tube" - particularly with the precision uppers. That said, I think I remember torquing my last .223 build to 60 lb-ft and then lining up the next hole. It shot well, but it didn't meet my 0.5 MOA standards. Barrel wasn't "match grade" anyway.
I wish I could remember what torque we used to install the White Oak 24 in Match barrel in a friend's upper -- that shoots one-hole at 100 yds with 60gr Vmax's.
Lapping is messy. Make sure you clean every last bit of grit or it will affect your torque readings.
After barrel assembly, the next trick is to use a clamp-on gas block. After that, it is aligning the gas tube with the bolt carrier key. After that, well, everybody has tricks they prefer but I can't prove any of mine make a significant difference on the target.
Hope this helps.