First to  check the FS to make sure that you did not bend the last inch of the threaded barrel, and not having bullet strikes to the inside of the FS. If you did bend the end of the barrel (have bullet strikes to the inside of the FS), then the barrel needs to be sent off to have the old threads removed (barrel slightly shortened), and the barrel re threaded.

Next, Pull the barrel off the upper receiver, and check to make sure that the upper receiver barrel socket is not cracked. If you did crack the upper barrel socket, then you will need a new upper receiver.

When you reinstall the barrel (read if receiver is fine), moly lube on the threads and bearing areas of both the socket and extension, and the barrel nut needs to be tighten on the receiver to 35lb to start with, the tightened more (not to exceed 80 ftlbs) to index the top channel in the barrel nut to the upper receiver gas tube channel.

When you reinstall the gas block with gas tube, make sure to index the block passage with the barrel gas port, and using carrier with key (no bolt) dry fit the carrier into the upper receiver to make sure that the end of the gas tube is correctly indexed with carrier key.  If the gas tube needs to be tweaked to align it correctly with the carrier key, then tweak the gas tube over the center of the barrel.


At this point, you can reinstall the float hand guard system.

Dropped it????
Hell, A service rifle should be able to pass a 15yards fling test!!!!

It's the range/safe queen rifles that don't see able to past the fling test instead.

When you removed and reinstalled the barrel, was the indexing blind pin still in place on top of the barrel extension?  Also by chance has the barrel come loose from the barrel extension, check by trying to unthread the flash hider from the barrel.  Have you tried the rifle with another optic or iron sights to see if it groups, just to eliminate that it is not the scope?

CY6
Greg Sullivan "Sully"
SLR15 Rifles
TheDefensiveEdge.com
(763) 712-0123

With no vise, how did you hold the complete upper when you retorqued the barrel nut?   This is usually done in a vise with some sort of way to brace everything, like the the barrel in block blocks, or the barrel extension in a lugged rod, or the upper receiver in a fixture.

CY6
Greg Sullivan "Sully"
SLR15 Rifles
TheDefensiveEdge.com
(763) 712-0123