equipment_failure

should-be-58.JPG Mon Jul 27 11:00:20 2009 original - 205 kB	should-be-59.JPG Mon Jul 27 11:00:49 2009 original - 285 kB	should-be-60.JPG Mon Jul 27 11:01:54 2009 original - 333 kB
is-61.JPG Mon Jul 27 11:00:02 2009 original - 289 kB	is-62.JPG Mon Jul 27 11:00:07 2009 original - 278 kB
fixed-63.jpg Tue Jul 28 19:57:23 2009 original - 210 kB	...or not, it turns out. It lasted better than the first time, but still failed after about 40 shots. I managed to finish my round though.
second-failure.jpg Tue Fri 14 2009 original	I clearly didn't understand the nature of the failure the first (and second) times. The red arrow is where the hammer was catching on the bolt carrier, preventing it from going forward into battery. I was fixing the loose carrier and not the hammer catching. It's pretty easy to see my crappy weld here. The failure isn't all that surprising I guess.
cleaned-up.jpg Tue Fri 14 2009 original	This time I ground down both parts of the bolt carrier so there'd be plenty of space for weld, and so there'd be lots of really clean metal to weld to. (duh, another newbie mistake)
done.jpg Tue Fri 14 2009 original	I put a lot of weld on (and you can see I'm getting better at it) and ground down the front edge so the hammer won't catch on it. Vertical thickness/shape isn't important in this area, so I'm not concerned with the blobby-ness of the weld. It cycles well, which is the only test I've done so far.
broken-again.jpg Sep. 14 2009 original	Well, it turns out I was missing how it was put together, it failed again after about 30 rounds or so. Some desctructive testing (grinding and full disassembly) revealed that the two square notches with punches aren't meant to hold it together under use, theyre only there to hold it together for welding. There's a round hole drilled in the action bar that's used to weld the carrier to the bar. It was welded at the factory and then ground flat and blued. I couldn't see it at first because I was seeing the much more obvious (but misleading) failure. This time I removed the bolt carrier entirely (which showed the hole in the action bar), ground the carrier down for fresh metal, re-drilled the hole in the action bar, ground down the two rectangular locating bits, and filled everything I could with weld. It's not as pretty this time, but I don't think it matters. It only has to push the hammer back.
5500-fixed-final-1.jpg Fri Jul 23 2010 original	5500-fixed-final-2.jpg Fri Jul 23 2010 original
I did run into one problem: I didn't clean up the sharp edges enough and some tiny piece broke off and jammed up the trigger mechanism. That was dumb on my part. But the bolt carrier hasn't broken for over 350 rounds so far and I can't see any cracks so I suspect this did the trick. After the trigger jammed I sanded down all the sharp edges so nothing could chip off and cause the same problem again.