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Posted: 1/4/2006 8:11:00 AM EDT

Hi. I have a 16” Bushmaster Lightweight that shot flawlessly up to this point. I have had three jams in short order and no longer trust it. I did a little research and it seems like the gun may be short stroking. The strange part is I shot 500rds of wolf through it without one jam when I got it. A few months back I got a military .22lr conversion kit for it. I put maybe 700rds through it with frequent cleanings. Now that it has jammed a few times with 5.56 ammo I am concerned that maybe it got some led in the gas hole from the .22s. Could this have happened? If so, how can I fix it?
Link Posted: 1/4/2006 8:14:33 AM EDT
shoot brake cleaner through it

shoot 5.56/.223 through to clean it out

check your mags

explain what type of jams you are having
Link Posted: 1/4/2006 8:26:00 AM EDT
The jams I have had have all been the same FTE. The bolt has caught the spent brass by the neck, so it sticks out of the gun like a stove pipe. The hammer is back and a bullet is in the chamber. I dont understand how this jam is happining.
Link Posted: 1/4/2006 9:28:37 AM EDT
lead fouling in the barrels hole for the gas port?
Link Posted: 1/4/2006 10:17:27 AM EDT
Replace the mag, and shoot some hotter ammo to see if it works OK. If it does, try the wolf again. I'd doubt lead plugged the port up as I have a lot of .22 thru one upper and It shot fine when I tried it with .223 ammo.
Link Posted: 1/4/2006 11:59:19 AM EDT
I shoot a .22 conversion in my M16. After about 100 rds of 22, I would shoot some .223. Recently, I shot about 500 .22's through the gun with no .223. I gave it a thurough cleaning, but I had the same problem you had. I removed the gas tube and there is some carbon/lead built-up in the gas port and gas tube. I cleaned the tube, but without removing the front sight I couldn't do much there. I put it back together, but the problem was still there. Looks like I have a dedicated .22 upper. Oh well!
Link Posted: 1/4/2006 12:18:29 PM EDT

Originally Posted By ak007:
Hi. I have a 16” Bushmaster Lightweight that shot flawlessly up to this point. I have had three jams in short order and no longer trust it. I did a little research and it seems like the gun may be short stroking. The strange part is I shot 500rds of wolf through it without one jam when I got it. A few months back I got a military .22lr conversion kit for it. I put maybe 700rds through it with frequent cleanings. Now that it has jammed a few times with 5.56 ammo I am concerned that maybe it got some led in the gas hole from the .22s. Could this have happened? If so, how can I fix it?



Ive heard about fouling in the gas port with the 22 conversion. I believe the .22 is a .221 diameter bullet, vs .224 for the 5.56mm. So it bounces around in the barrel and can easily get lead, powder, and other crap caught up in the port and the rifling grooves.
Link Posted: 1/4/2006 12:36:30 PM EDT
.22LR bullets are not so small compared to the 5.56mm bore that they 'bounce around.' Instead, they expand at their base and do a pretty good job of engaging the rifling; they'd be useless as a training aid if they weren't fairly accurate, and you CANNOT have accuracy with that undersized a bullet.

The manual for the M261 calls for firing "a full magazine" of 5.56mm ammo through the rifle after firing 400+ rounds of .22LR. This is supposed to clear fouling in the gas system.
Link Posted: 1/4/2006 12:42:17 PM EDT
.22LR and 5.56 are both the same size -- .224".

Lead from .22LR bullets can definitely constrict the gas port and cause short stroking. More than likely, you'll have to pull the FSB to clean out the gas port.
Link Posted: 1/4/2006 1:28:01 PM EDT
[Last Edit: 1/4/2006 1:28:56 PM EDT by FALARAK]
Also - if anything else has changed - make sure you check ammo (try some M193) and check your gas key on the carrier. Bushmaster like to get loose around the 1000 round mark..... or at least they used to.

And dont just wiggle it.... torque it down. If you can tighten it at all... it was loose. Remove, scrub, clean, dry, reassemble, and stake the hell out of it.
Link Posted: 1/4/2006 1:49:35 PM EDT
If it is indeed a lead problem in the gas system you could simply tear the upper apart completely and clean it. Remove the gas tube and clean it well with carb cleaner. Remove the FSB ( pain in the ass ) and clean its gas port, as well as clean the gas port in the barrel. Reassemble and shoot some of the hottest ammo you can find. Mil-surplus would be the best. Make sure your carrier key is tight, as well as all your gas rings intact.
Link Posted: 1/4/2006 1:56:52 PM EDT
Are you cleaning and lubing per the TM, with CLP? Are you using a chamber brush to scrub/clean the chamber?

Have you tested the one round in mag-lock back test? That determines if you are short stroking. This could be all kinds of things. Ejector, extractor, chamber issue, clean, lube, etc....
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