AR Sponsor
Posted: 9/22/2006 11:37:59 AM EDT
|
Guys I need a fresh set of eyes here.. -Bushmaster 16" M4 barrel -RRA auto boly group with D-ring -CMT flattop upper all of which is brand new.. The gun has a M4 stock with standard buffer and spring.. The gun is short stroking with with Wolf 55gr, Q3131a, and Talon tracer.. Will not hold bolt open on empty mag.. The Q3131a worked the best but not right.. I have checked the gasport .063 and free of burrs or obstructions.. Gas rings are not aligned and the carrier key is tight and not leaking at all.. The gas tube is aligned with the carrier key perfectly.. I have tried a totally different bolt group and the upper on 2 different rifles and nothing.. I think that is all.. Do you think it still needs to be broken in or what?? I gotta get this thing going, it has given me more problems than my 7.5in full-auto upper.. Thanks |
|
Is the FSB aligned correctly with the gas port? Loose or tight? If you have a gas block lying around you could test gas port to gas block alignment. Also, anything blocking the gas tube? Which buffer are you running? There's a big pinned thread in the Troubleshooting forum dealing with short stroking. I feel your pain - my Stag 6.8SPC carbine short stroked until the factory finally managed to fix it on the second try... |
|
I am guessing it is aligned and the burn pattern on the barrel says it is.. The FSB is real tight.. I just pulled the gas tube and it is free of obstructions and the gastube hole alignes with the FSB hole perfectly.. It is a standard buffer.. I read the pinned thread and have done everything it suggests.. I used it to get my 7.5in upper going also but this upper has me stumped?? Thanks |
|
perhaps this is an imbecillic response, but are you using a enough lube (carrier)? from what it sounds like, you've covered all the bases...even using nato pressured rounds with the same results. is the carrier dragging on the mag. feed lips?  just throwing stuff out there. good luck getting it running. |
yeah i lubed the snot out of it. i don't think it's dragging, i tried a bunch of mags thanks |
Tight is only one part of it. Is it aligned correctly with the gas tube? (He does mention this so it's fine) Is it flush to the top of the carrier with no signs of gas leaking? ETA: Since it seems to be ejecting fine and it's jsut a problem with the bolt locking back: - make sure there's no burr slowing the movement of the bolt catch. - make sure the tension on the mag release is correct to hold the mags in place. - try a heavier buffer. Running a 16" carbine barrel with a standard lightweight carbine buffer may be allowing the bolt to cycle too fast for the bolt catch to operate. |
Yes the carrier key and gas tube fit perfectly.. I closed the bolt and put a couple drops of oil in the key then blew air down the key and nothing came out the base of the key. I will check for a rough spot in the chamber.. Is their a good way to do this or just by sight?? Thanks I tried the upper on a different lower so it has to be somthing with the upper not the lower.. I will try a heavier buffer but I didnt think that it was possible to over gas a 16in with a .063 gas port.. |
there you go. both my carbeans have an H-buffer. no problems yet. |
cotton q tip swabbed inside the chamber is one way I've done it. a little burr will snag the cotton fibers. |
|
I just checked the chamber with a q-tip and flashlight and it seems smooth.. I guess I am going to pack up and head to the range. This is what I am going to try in order: -Different buffer and spring H-buffer -Take out D-ring -Swap gas tubes Any other ideas for me before I make another trip to the range with this thing.. Thanks |
|
thishttp://www.ar15.com/forums/topic.html?b=3&f=66&t=240052&page=1 might help w/ diagnosis since you already tried different BCGs, the problem sounds like it might be your tube or the gas block; i guess you could try a heavier buffer, but if it does not work w/ a std buffer, there is somehthing else wrong |
AR Sponsor