Any signs of gas leakage around the front sight base where it mates with the barrel?  Also start with a thorough cleaning, then make sure you lubricate the 7 bolt lugs and rails of the bolt carrier so they are good and wet with a quality lubricant like Slip2000 "EWL" Extreme Weapons Lube.  What length of barrel?

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

Ditto with Sully,

Start with a full CLP clean of the rifle, including using a chamber brush and CLP to scrub the chamber, to remove all the assembly/Storage grease from the rifle to begin with.

On the gas block front and back, and even gas tube to the gas block, CLP around the seams, then with a piece of rubber tubing on the end of the gas block in the upper receiver, pressurize the gas tube to around 100lb with air.  The air should be flowing out the bore of the rifle via the gas port, but the gas port will allow enough back pressure to check for gas leaks of the gas block to barrel and gas tube.  On the B/C, CLP around the base of the key, then while holding the bolt inwards, pressurize the key to 100lb with air. A light bubble or two of the gas tube to block is semi normal, but leaks anywhere else is not.


That weeded out, pull the bolt off the carrier and dry fit the carrier with key in the upper receiver.  The carrier (side of the key really) should not be binding in the upper receiver, and when the front of the carrier get about a 1" before front of the carrier touches the back of the barrel extension, will be the mating of the gas tube to the key to confirm that the gas tube is correctly indexed for the key as well.  Also, what did you ammo did you spec the barrel for?  If for 69gr ammo, then the gas port is reamed on the smaller side, since the heaver ammo will be using slower burning powder that will produce higher port pressure due to the dwell spike of the powder burn being closer to the gas port than say standard ball ammo with normal burn rate powder instead.


From there, take a good look at the top and bottom barrel extension lugs indexing, and make sure that the barrel did not slip when the barrel nut was being tightened, and the barrel extension is not now canted in the upper receiver to cause bolt lug binding on the lock and unlock.


Rifle back together, pull the handle all the way back, and make sure that the face of the bolt stops around 1/8" to 1/4" in front of the back edge the  ejection port window.   Also, when pulling back on the charging handle, the middle of the pull, the last of the pull should be the same tension.  If the last inch of the pull gets a lot harder, then you have hammer wedging going on.   If the bolt face will not come back far enough, bank that you have the wrong length butt stock bolt in play (too long for the stock you are using), and the tip of the bolt is now protruding into the back of the tube instead.

Lastly, being that this is a white oak NM barrel, did you send them the bolt so they could head space the barrel to bolt, or at least checked the head space of the barrel with the new bolt yourself?  If the head space it too tight, or you are ending up with bullet embedding at loading, then can cause higher than normal working pressures, and will cause short stroking as well.

Still don't see an answer if the key is leaking to the top of the carrier.
When you install the gas tube in the FSB, did you check to make sure that the bottom gas tube entry channel was aligned with the gas block channel?  Trust me, if you don't check, just too easy to have the too off, or worse with the roll pin driven through the the FSB in front of the gas tube, instead of through the gas tube channel for it.

Also, what size was the gas port on the barrel?

20" barrel, .750" dia., 6.875" from muzzle;
Port sizes from .093" to .096"

And being a NM barrel for heaver ammo, should have been closer to the .093" range.

As for crap inside the receiver extension, double check the end of the spring winds for burs that may need to be filed down, as well the buffer bumper roll pin not flush with the sides of the buffer, and it needed to be filed down to flush out with the sides of the buffer as well.



As for the bolt feeling gritty in the carrier, remove the gas rings with your thumb nail one by one so you don't break them, and dry fit the bolt to the carrier without the rings to see if it still feels gritty.  If not, then when you install the rings back on, keep in mind that the gas rings are stamp cut, with the top of the ring edges rounded, and the bottom edges inside and out sharp instead.  So when the rings get re-installed , all the top rounded side face the front of the bolt, and the sharp edges face the tail of the bolt.

Hence this puts the sharp edge against the round edge of the next ring against it, and with the sharp edges to the rear, give a better seal as the gas it pushing against the rings to cam the bolt outwards in the carrier.
Note, if the sharp edges are really bad, then light touch with 400 sandpaper to remove some of the sharp burs will resolve the problem, instead of just letting rifle break-in smooth the sharp ring edges instead.