The barrel on my rifle seems to be slightly loose. It will rotate enough for the Frontsight to move about 1/8", but the barrel nut is tight and will not move.

What should I do?

I assume the gas tube is not what's keeping the barrel nut from moving?

If the barrel nut is tight and the barrel still twists it must be a loose barrel extension.  The barrel extension has the teeth that the bolt engages and a shoulder that the barrel nut clamps down on.  The barrel is threaded into it.

It may be cheaper to buy a new barrel than fix the problem.  I suspect the barrel extension will not be "clocked" to the front sight after properly torquing it.  If so, the barrel would have to be machined off slightly less than one full thread.  This would require rechambering the barrel(not a good idea with chrome lining).

Moving 1/8" might mean that the barrel is slipping in the receiver and that distance is just the extension pin hitting the each side of the receiver extension pin slot.  If the barrel extension were loose, then the barrel would just spin out until it bent the gas tube.


To fix a loose barrel in the receiver, you will need to remove the gas tube, vise the upper in a upper vise block, and tighten the barrel nut up to 35lbs, then a little more to get the barrel nut spines correctly indexed to allow the gas tube to pass threw.