Case not ejecting on a fired round

[montana]

It can be many reasons why your rifle is failing to eject. First thing is to check your chamber to make sure it will pass a go- no go gauge. A tight chamber can cause excessive pressures resulting in function issues. More than likely it is a gas issue. The best way to check the gas block- barrel port alignment is with a bore scope and a lighted gas tube. Check the gas block barrel journal fit for excessive gas leakage. Then move back from there by checking the gas block- gas tube interface and check for excessive gas leakage, check the gas tube for any cracks or leaks, check the gas key-gas tube interface. Using a pin gauge the gas key I.D. should be .180 to.182. A Mark Brown custom gas tube gauge checks the button on the end of the gas tube for excessive wear, that can cause excessive gas leakage. Most gas leaks occur between the gas key and the bolt carrier. The gas key screws may look fine but can have a broken screw or be loose. The gas key screws should be tightened to 55 to 58 inch pounds. Mill spec requires a gas sealant between the gas key and carrier, but many companies do not do this. The inside of the bolt carrier has three bores that may or may not be gas efficient, especially between the bolt tail and bolt tail bore. Do the gas ring test on your bolt carrier group. If all else fails, then it may be necessary to open the barrel's gas port. One area I always check, "especially with the Grendel bolt" is the extractor. If the extractor has the rubber O-ring, I will remove the O-ring if the extractor spring is strong and the extractor spring has the black plastic insert, see if this helps. Too much extractor force can cause function issues.. If you have a JP SCS with tungsten weights, it is very easy to take apart and change weights. JP has a video on how to do this..There can be other problem areas such as barrel clocking in the upper, buffer tube alignment and depth, fire control group problems, etc. Good luck...