Caduceus
07-31-12, 20:58
So today I went over to my local indoor range - only 25meters, but it's only 20 minutes away. I have a new (to me) LMT 16" M4 upper bought of EE, and a new LMT bolt (headspaced and passed w/ Go and No-go gauges). Mounted it on the only lower I have, a S&W that normally holds the 15OR upper.
Reportedly this upper has about 500 rounds - I've put about 150 on it so far, nearly all M855 (federal ammo cans) or M193 (PMC X-tac). It's been a bit finicky on the last round and not holding the bolt open
Anyway, today I load up, go to sight in my new ACOG (again, of EE). First round fires, and doesn't cycle the bolt. I look, and BCG is only showing the bolt at the rear end of the dust cover. I can rack the charging handle and lock the BCG to the rear but it won't release. Remove the mag, try a few more times, and come off the line. Off line, am unable to separate the upper and lower - the pins come down, but the BCG is stuck halfway into the buffer tube.
Get some help from the range guys, grab their tools, and have to unscrew the buffer tube. All sorts of little pieces come out, but everything looks intact (detent pin, spring, etc). Manage to get the BCG out by pulling and tugging and cussing and finally it manages to slide forward enough to separate the upper and lower. On pulling the BCG out, everything looks fine. Put the BCG and CH back on the upper, and everything runs fine for about 10 hand-cycles, then suddenly it locks up again (at this point, just cycling the upper; the lower is on the table)
Anyway, end of the story is that the forward assist broke. Took me and another guy about 15 minutes to find the piece. Fortunately it wasn't in a life/death situation, but if it had been, the rifle would have been out of business.
Hopefully if this happens to someone else it'll clue them in faster than we were.
Once we pulled that piece out, I finished sighting in the ACOG. Need to go figure out how to replace the FA. The original S&W upper is now back on it's lower.
Edit: Pics per request. Pic one is the approximate position of the BCG/bolt when stuck. Pic two is an attempt to look into the FA port. Pic three is the piece off the FA. I tried to remove the FA, but the pin is pretty well in place.
http://i256.photobucket.com/albums/hh196/Caduceusmd78/DSC02341.jpg
http://i256.photobucket.com/albums/hh196/Caduceusmd78/DSC02346.jpg
http://i256.photobucket.com/albums/hh196/Caduceusmd78/DSC02347.jpg
Reportedly this upper has about 500 rounds - I've put about 150 on it so far, nearly all M855 (federal ammo cans) or M193 (PMC X-tac). It's been a bit finicky on the last round and not holding the bolt open
Anyway, today I load up, go to sight in my new ACOG (again, of EE). First round fires, and doesn't cycle the bolt. I look, and BCG is only showing the bolt at the rear end of the dust cover. I can rack the charging handle and lock the BCG to the rear but it won't release. Remove the mag, try a few more times, and come off the line. Off line, am unable to separate the upper and lower - the pins come down, but the BCG is stuck halfway into the buffer tube.
Get some help from the range guys, grab their tools, and have to unscrew the buffer tube. All sorts of little pieces come out, but everything looks intact (detent pin, spring, etc). Manage to get the BCG out by pulling and tugging and cussing and finally it manages to slide forward enough to separate the upper and lower. On pulling the BCG out, everything looks fine. Put the BCG and CH back on the upper, and everything runs fine for about 10 hand-cycles, then suddenly it locks up again (at this point, just cycling the upper; the lower is on the table)
Anyway, end of the story is that the forward assist broke. Took me and another guy about 15 minutes to find the piece. Fortunately it wasn't in a life/death situation, but if it had been, the rifle would have been out of business.
Hopefully if this happens to someone else it'll clue them in faster than we were.
Once we pulled that piece out, I finished sighting in the ACOG. Need to go figure out how to replace the FA. The original S&W upper is now back on it's lower.
Edit: Pics per request. Pic one is the approximate position of the BCG/bolt when stuck. Pic two is an attempt to look into the FA port. Pic three is the piece off the FA. I tried to remove the FA, but the pin is pretty well in place.
http://i256.photobucket.com/albums/hh196/Caduceusmd78/DSC02341.jpg
http://i256.photobucket.com/albums/hh196/Caduceusmd78/DSC02346.jpg
http://i256.photobucket.com/albums/hh196/Caduceusmd78/DSC02347.jpg