When working up load, single mag load your starting point load, and make sure that the bolt locks back on the catch.

I state this since the action requires smaller range of pressure at the gas port to cycle the action correctly, and although your over all working pressures may be within spec, the pressure to the gas port can very a great degree depending on the burn speed of the powder being used.

With a faster than normal burning powder, the peak burn of the powder is closer to the chamber, ending up with the gas port lower. On the other side of that coin, slower burning powder pushes the pike burn spike closer to the gas port, which increase the amount of pressure that gas port sees.   And again, this is all independent for the most part of the actual total working pressure of the round.

As for standard powder burn speed for 308 mil type gas actions, you can use 4895/4064 since this was the standard powder used for a very long time in the ball 30-06/7.62 nato loads for 150-147gr FMJ bullet ammo (until they switch over to ball powder burning around the same speeds).

Being that these where reloads, start by checking the spent primers in the spent cases to make sure that the loads are not going over pressure. Could be either reduced case volumes for the reloading data your using, or even OAL of the loads too long and you have bullet embedding on loading. Lastly here, make sure that you are working the loads up from the starting point of the data, and not just jumping to max powder levels instead.

Next would be to make sure that you have the chamber scrubbed clean via a chamber brush and CLP, are using a solvent to clean the rifle that is not leaving behind a residue like Hoppes does, and that you are lubing the bearing areas of the upper  correctly with CLP.

From there, we get into the start check for spent dropped case from the bolt that do not clear the action,
Start with pulling the charging handle all the way back, and confirm that the face of the bolt stops about 1/8" to 1/4" in front of the back edge of the ejection port window.  If the bolt is retracting back to far, you can pull the buffer and spring, and drop a quarter or two into the tube void to shim the end of tube forward.

Next pull the B/C, hook a spent case on the extractor and cam the eject into the bolt face a few times to make sure that the ejector is not binding in the channel for it.  If the ejector checks out to move without binding, then pull the extractor and make sure that it bur free at the grabbing claw surface and the edges of the rim relief channel so the extractor is getting a good bite on the spent case rim.

If the loads will lock the bolt back on the catch via single mag loading, the stroke is fine.

The spent case is pivot off the bolt face at the back of stroke stall, and if the bolt is behind the ejection port window, then the case is pivoted off the back of the ejection port window, and can end up back in the action.

Since the upper does have a port window cover, then should not have the problems of the short window of the LR slab side upper, and should be able to band-aid shim the back of the tube forward with quarters to stop the bolt in front of the back of ejection port window on the end of rearward stroke (but still behind the bolt catch).

Hand cycling anything out will not clue you in the problem at hand.

As you start to pull the CH back, the ejector is already trying to cam the spent case off the bolt face (why hand cycled out cases/rounds have scratch marks from the cases scrapping off the right hand side barrel lugs).

During fired cycling, the spent case is pressure forced against the face of the bolt via residual bore pressure until the bolt is all the way back (ejector just starting to push the spent case off the bolt face the last part of the rearward movement), and at the back of stroke/rear buffer stall (since the buffer works like a dead blow hammer), that is when the spent case is then pivoted off the bolt face to cause the spent case ejection pattern to be at the normal 4:00 to 5:00 direction out of the port.

Its this back of stall when the ejector really goes to work to pivot the case off the bolt face, that either the spent case can clear the ejection port window back edge, or  tag the back of the ejection port window to be defected back into the action instead.


To add, ejector spring tension strength does come into play, being that if the tension is not great enough, it can allow the extractor to slip off the rim of the spent case on the initial pull of the case out of the chamber, leaving the case in the action as well. Rem is pretty good about using known quality extractor springs, but if push comes to shove with the face of the bolt stopped at the correct relationship to the back of ejection port window and still having problems, may want to upgrade the extractor spring to extra tension spring (or just add a O ring around the extractor spring to add more that way as a band aid).