[My CMP M1 field grade is ejecting its clip with live rounds about half way through firing./QUOTE]
If the follower arm and follower arm pin are worn, it is quite common for the clip to eject with one or two rounds remaining in the clip. If yours is ejecting with four, doubt that this is the problem, but see if there is a lot of play between follower arm and pin.
I maintained our club's DCM rifles for a lot of years and that was one of the most common malfunctions and we completely wore out 4 rifles during that time frame.
One little trick you can use when pin/follower wear is the problem is to place the follower arm loosely between the jaws of a machinist vice with the pins supporting the arm. The arm will be in same attitude it would be in the rifle when it is being fired, that is w/curve on top. Measure the distance from the top of vice jaw to the top of the follower arm about half way between the pins; now, using a 1/2" or so diameter brass punch, place punch at spot where measurement taken and hit w/a medium size ballpein hammer. May take a couple of taps to bend the arm, but bend it 1/64 - 1/32" (This is a hammer fit, guys
). Put it in the rifle and give it a try. I like to have new arm/pin on hand just in case, but have never had this "hammer adjustment" fail to correct ejection on 6th or 7th round.
Regards,
hps
PS The only parts I found necessary to replace over the years were (in order of numbers replaced):
Follower Arm & Pin
Firing Pins
Extractors (and ejectors that flew out and were lost when extractor failed)
Op rod spring
Sent 4 back for new barrels after we shot them out