cyclopsshooter
Member
i forgot to mention that is seems more reliable when doing a rapid fire mag dump...
Bushmaster Jamming Problem
- Thread starter cyclopsshooter
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Not sure if it has been mentioned (long thread) but try a pmag. Bushmaster mags suck it hard combine that with low powered ammo and you will have problems. My bushmaster acted like you are describing. I switched to pmags and like that the problem went away.
Z-Michigan
Member
Huh? All the "Bushmaster" branded mags I've seen are made by one of the GI contractors, probably D&H. Or are you talking about only the blocked 10-round magazines due to the NYS ban?
Bartholomew Roberts
Member
What you describe does not sound like a short-stroking problem (gas port/gas key/gas rings/etc.) For a new round to be chambered with an empty, one of three scenarios is likely:
1. Ejector doesn't work properly and empty case is dislodged as bolt scoops up the next round.
2. Extractor loses grip and drops empty case before the ejector can work.
3. Magazine feed lips are too wide and spit next round into receiver before empty has extracted. New round dislodges empty and causes stoppage.
Now you say the ejector works fine and the mags work fine in other rifles. You also say the extractor claw is sharp. That leaves a weak extractor spring among likely culprits. You mention that the problem decreases as pressure/heat increases (rapid fire). This makes me think weak extractor spring. Often the extractor will lift off the case for a few microseconds during extraction. Usually the residual pressure is enough to keep the empty on the bolt face until the extractor snaps back into place. I am thinking that your spring is taking too long to grab the rim and the case drops off the extractor.
Try adding an O-ring to prevent lift in the first place or a beefier M4 extractor spring (Bushmaster used to use the weaker rifle extractor spring, even in carbines).
1. Ejector doesn't work properly and empty case is dislodged as bolt scoops up the next round.
2. Extractor loses grip and drops empty case before the ejector can work.
3. Magazine feed lips are too wide and spit next round into receiver before empty has extracted. New round dislodges empty and causes stoppage.
Now you say the ejector works fine and the mags work fine in other rifles. You also say the extractor claw is sharp. That leaves a weak extractor spring among likely culprits. You mention that the problem decreases as pressure/heat increases (rapid fire). This makes me think weak extractor spring. Often the extractor will lift off the case for a few microseconds during extraction. Usually the residual pressure is enough to keep the empty on the bolt face until the extractor snaps back into place. I am thinking that your spring is taking too long to grab the rim and the case drops off the extractor.
Try adding an O-ring to prevent lift in the first place or a beefier M4 extractor spring (Bushmaster used to use the weaker rifle extractor spring, even in carbines).
I am having the same sort of problem with mine. Brand new had it out twice and multiple FTE every mag. I have used different mags, ammo. Mine from what I can tell will extract the spent shell then try to feed it back in with the new round. The neck of the spent shell will be dented/crushed when I finally get it out. So I am assuming the it is being fed back in and being dented in the process. Took it apart cleaned and lubed it and am waiting to see if that is going to help.
cyclopsshooter
Member
i pulled the bolt apart and it was full of caked on gritty grime- thoroughly cleaned it and coated the carrier and bolt with fresh gun oil-
the bolt moves much more freely and smoothly now
i test fed a mag (on safe) and it worked flawlessly... hopefully i will get a chance to fire it in the next few days
the bolt moves much more freely and smoothly now
i test fed a mag (on safe) and it worked flawlessly... hopefully i will get a chance to fire it in the next few days
Feed issues on a new gun can also be solved by tightening the mag release. This fixed the issues I had with known good mags (used and new) that worked fine on another rifle.
Push the button for the mag release in until the mag catch clears the lower on the opposite side, and turn it clockwise once. I've had no feed issues since.
Kris
Push the button for the mag release in until the mag catch clears the lower on the opposite side, and turn it clockwise once. I've had no feed issues since.
Kris
Jed Carter
Member
Anyone who is giving any advice that is not specifically focused on the extractor/extractor spring, is not giving advice. The bolt carrier group is cycling, so lube, gas rings etc. are not the problem. It could be the ammunition, the coated steel case stuff can GLUE itself in the chamber, most common in a very hot AR. I would (and have myself) change the extractor and spring, it should and has cured my nonextracting AR. Of course all cycling/extracting problems would be just unpleasant memories if you trade your AR for a SIG 556.
Bartholomew Roberts
Member
Always good to do; but that is unlikely to solve the problem you described. Believe me, my bolts have gotten plenty gritty and dirty. Typically, you would need several thousands of rounds through a rifle to get the extractor dirty enough to fail (I clean out the channel under my extractor maybe once every 4,000 rounds or so and have never had a problem).
Short of a whole lot of shooting, the only way cleaning would be helpful for lesser round counts and this particular problem is if brass had bound the ejector. Sometimes in tight chambered guns, brass will extrude into the ejector pin hole and get bit off as the ejector cycles. If this is the case, you'll see tiny, tiny bits of brass in the ejector pin hole. However, since you say the ejector was working fine, I am guessing this did not happen.
Again, I'd replace the extractor spring with an M4 extractor spring and consider an O-ring or similar insert as well.
wally
Member
I've had an out of spec extractor. Everything looked fine but it was unreliable ejecting. Replacing the spring and O-ring didn't help.
Turns out the gap between the hook face and the bolt face was a few thousands too narrow so it wasn't slipping completely over the rim. Remove the bolt and carrier and verify the rim actually fits under the extractor. I replaced it and all was well, but I also confirmed my diagnosis by filing the defective extractor so the gap was wide enough to slip over the rim, problem solved.
--wally.
cyclopsshooter
Member
Final report
Ok guys, i ran 80 rounds tonight without a single hiccup- one 20 rounder and two 30s- the problem was the funky bolt- cleaning and lubing was the answer
thanks to everyone who took the time to trouble shoot with me
Ok guys, i ran 80 rounds tonight without a single hiccup- one 20 rounder and two 30s- the problem was the funky bolt- cleaning and lubing was the answer
thanks to everyone who took the time to trouble shoot with me
Congrats on getting it running. Usually it is the simple things and people like to assume the worst when they hear bushmaster for whatever reason. So much for this guy's condescending advice (anywho looks like his post got deleted):
As everything breaks in it will run better and better.
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