When we got the C7/8/9 in the fall of 1987 in Lahr, the whole of 4CMBG had to change all at once - on a Friday night at 1600 hours - because we were all on two hours notice to move, and the ammo outload packs on the 548s had to change as well.
The next while we had some problems. the magazines, which I won't go into on this post, and the ejector springs.
We got some bizarre stoppages. some 'Bolt over Base' which are common mag probs, but a lot of 'disco' stopages, where a cartridge and an empty casing were dancing around in the receiver together. Often, the empty case would be trapped with it's mouth over the gas tube orifice. since the front of the cocking handle rests around the gas tube, this meant that attempting to cock the wpn meant trying to crush the casing between the front of the cocking handle and the boltface - not doable.
I had our Boeselager shooting team put a section of cleaning rod in the loops of their 1982 pattern yoke so they could use it to pull the bolt to the rear without using the cocking handle, allow the casing to fall fre, and carry on. Bad mags were culled and crushed during training shoots.
Turns out, half the stock of ejector springs was improperly heat treated and thus too powerful. There is a balancing act between the two springs in the bolt. The ectracter spring has to be strong enought to allow extraction, but weak enough to allow the ejector spring to overpower it and pivot the casing past the extractor once the casing is no longer in contact with the wall of the chamber. If the ejector spring is too weak, it won't overpower the extractor spring at this point. If it is too strong, it will overpower the ejector spring before the casing is fully clear of the chamber, and push the casing forward past - rather than pivot around - the extractor. Hence, the casing may not leave the receiver, and may in fact try to snuggle the gas tube, while the next cartridge is being stripped from the mag and attempts to chamber.
Talk about a frustrating year THAT was.
The SARP Newsletter at the time I think said the C7 was capable of 1,000 RBTF (rounds between failure).
We should be at that now, all things being equal.
Cleaning: at the time - 1987 - the bolts and bolt carriers were not serial numbered to the wpn. Since the 'dirty parts' of the gas system were now on the bolt carrier assy, and since no one ever got the same bolt, no one bothered to do a real good job cleaning them. After the first two shoots, I got some baggage tags from the AMU and - much to the initial consternation of the SQMS shop (who then saw the method to my madness) - tagged each guys bolt carrier. "What you clean is what you get" I said. Worked.. spotless carriers, spaced gas rings, cut stoppages by 90%.
Tom