Quoted:
It (Spent Casings) has started hitting the forward end of the opening where it ejects.
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What location on the front of the ejection port is being contacted by the spent case, the inside, and the outside or just at the lip between the inside/outside of the front of port? The location of contact will determine the plan of attack to correct the problem.
If it at the outside, then the bolt is releasing the spent case too far behind the ejection port on buffer stall, and the rear of the spent case is deflecting off the rear of the ejection port, and spinning the round forward to make contact.
If the contact is at the inside, then the extractor is not retaining the spent case, and the ejector is pushing the front of the spent case over, and scrapping the port on the way back. This is also a sign of ammo high working pressure, with the BC losing too much momentum at ejection by having to pry the blown out case off the chamber walls.
If the contact is at the lip, the extractor or ejector is faulty, and the spent case is returning forward with the BC (not pivoted off at buffer stall) and being shoved into the front lip of the port.
The second two are easy fixes, the first is a little harder, due to having to limit the rearward stroke of the BC/buffer, and requires that the receiver extension contact point and threaded end be slightly shortened to limit the amount of travel that the BC can run backwards. Also, the easy way to see if free run is the problem is to just lock the bolt back, and see how much room the bolt will move back away from the bolt lock. The range should be around .020-.045 free run past the bolt lock (bolt should stop before reaching the back of the ejection port), more than this and the case is just spun against the back of the ejection port on release from the bolt on stall.
As for the AR-10, I haven’t pulled one down in a while, and can’t remember if the Armalite buffer has tungsten weights (My last SR-25 was solid plastic). Without the dead blow weights, the buffer/BC does not stall on end of stroke, and the ejection path of the spent case is forward, not spun out rearward at stall. My solution to the problem was polish the ejector pin/channel to make sure there was constant/smooth pressure getting the case off the bolt face, and to clean the burs off the ejector claw to make sure that the case had a clean release on the forward stroke.