
Took the JW21 (Chinese copy of the 9422) out for some offhand steel practice in 15-25mph winds and rain to see if I could learn something (other than the obvious!)

Put 15rds on the chicken with about 50% hits (after I had this issue when I got back out there everything had blown over so I didn't bother inspecting the targets). Put nine on the pig (one dropped shot), then had a fail-to-fire. The previous three rounds or so had needed a bit of an extra pressure toward the end of the stroke to chamber them but it didn't strike me as a mechanical issue. The ftf had a good dent, but it was toward the centre, not the rim. I popped it into the end of the magazine and continued. But the rounds were ejecting as soon as they came out the top of the bolt grooves. Back to the office for a look...
I think I can see the problem

The left extractor has been flattened against the bolt face. It's job is to hold the case head against the bolt face to keep the cartridge aligned to feed cleanly into the chamber, and to apply rightward pressure against the case to keep it hooked behind the primary extractor during extraction.
It must've developed a burr on the bottom that caused the rising cartridge rim to bend it up instead of pushing into position behind it. This would've been the glitch in the cycling, until it was so bent it became caught behind the case head and flattened out, resulting in the bad strike - I'm amazed the action even closed on this! After clearing the failed round, the next rounds were coming off the top of the bolt grooves and immediately being ejected by the obstruction of the bolt face.
I dug a spare out and had it replaced in a few minutes.
So I need to order some more spares. My dealer can't get Winchester (or Norinco) stuff so I'll have to order parts from Rebel's.
I went back out to find my targets all lying down, except a plow disc. So I put the remaining 76rds onto it at 100m. All good, including the failure.
But I had a new issue

Several times a round came out of the magazine tube before the rim was locked into the lifter grooves in the bolt face, so I had a loose round floating around in the open action. The next round was properly caught behind the cartridge stop, so it doesn't seem to be a magazine issue. But it was happening in the last two or three rounds in the tube, when the spring is at its weakest.
Anybody able to give me a clue where to look for damage? I have a spare magazine tube spring I can try, and I can cut a piece of aluminium rod to restrict it to 10rds, while also compressing the spring by that unused five-inches. If that fixes it then I know it's just a weak spring. Are these known for issues in the lifter or cartridge stop though? I can order Winchester replacements of those as well if they are known for wear.