Pls help troubleshoot failure to feed in XM15

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bushmaster1313

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My Bushmaster XM15 is experienceing occasional failures to feed.

The spent case ejects fine but the fresh cartridge seems to be getting hung up on the ramp and does not go all the way into the chamber.

What are the possible causes.

Old main spring?
Dirty ramp?
Have not oiled for a couple of months?
Burr in the ramp?
Bolt is not moveing smoothly in its tracks?

This does not appear to be a stovepipe issue, but I could change the extractor spring.

I do not know how to change the ejector spring.

Thank you in advance.
 
Does this problem happen with multiple magazines?
Click to expand...

Yes, it does happen with multiple magazines.
And not all of the time.

Is it possible I am sometimes not jamming the magazine all of the way in?

Also, I noticed that the XM-15 does not have a ramp in the same way that a Sig 226 has a ramp.
 
It should have two feed ramps, left and right for feeding from the left and right side of the magazine.

What kind of magazines do you have?

Do the magazines have the newer style followers?
 
What type Ammo?

Does it happen with different weight and manufactured rounds? M855 or M193 or what?

Two Bushmasters I have will not shoot steel casings without the same type problems. Brass never bothers them.
 
I gave it a good scrub and lube about 2 months ago.
Then one month ago I shot 40 rounds and at the end I got a few failure to feed.
I thought it was the magazine so I got a fresh one out and did not have a ny problem for the last few rounds.
Today I shot 60 rounds and I got failure to feed in some of the last rounds.
Shooting UMC factory brass with Bushmaster 10 round magazines.
Lube with Ballistol.
 
AR 15's are very finnicky. sp?
they need to be stripped and cleaned often, with very much detail, even to taking the bolt apart. maybe you do need a new part, odds are you arent keeping it wet. ar's run wet.
(very lubed)
 
An AR does NOT need to be clean to operate correctly. If you AR only operates correctly when it's clean, something is wrong.

An AR DOES need to be lubed in the proper places to operate correctly. When an AR stops running, all it usually takes is a couple of drops of lube in the gas vent holes in the bolt carrier. I also like to keep the bolt lugs, bolt and carrier lightly lubed just to help displace the crud that builds up.

My question is how many rounds do you have on that buffer spring.

If you have more than a couple of thousand rounds through it, or even less. Just change it. They are cheap. Check the movement of the bolt within the carrier and make sure it isn't binding. Check the movement of the carrier in the upper and make sure that you don't have any binding there.

Just to make sure that I'm understanding, the bolt is peeling the top round off of the magazine, but isn't feeding it all the way into the chamber, right. Are you using ball ammunition or soft point?
 
My question is how many rounds do you have on that buffer spring.

If you have more than a couple of thousand rounds through it, or even less. Just change it. They are cheap. Check the movement of the bolt within the carrier and make sure it isn't binding. Check the movement of the carrier in the upper and make sure that you don't have any binding there.

Just to make sure that I'm understanding, the bolt is peeling the top round off of the magazine, but isn't feeding it all the way into the chamber, right. Are you using ball ammunition or soft point?
Click to expand...

It is probably time to replace the main spring.
I am shooting FMJ.
The spent cartridge ejects fine.
The bolt takes the new cartridge from the magazine and gets it about halfway into the chamber, but not all the way in.
net result is the shell is half way in and pinting up with the bolt smashed against the side of the cartridge
 
OK, so what you are seeing is the bolt jammed into the side of the cartridge? Man, although I'd go ahead and change that spring, maybe you're having a gas problem, or lack of gas problem. When you last lubed the AR, did you put a couple of drops of oil into the vent holes? It sounds to me like the bolt isn't coming back far enough.

Remove your bolt/carrier group, make sure that the bolt is extended, then carefully stand the bolt on a level surface. There should be enough ring tension so that the bolt/rings will support the weight of the carrier. If it collapses (bolt retracts into the carrier) under the weight, the rings are bad.

This sort of thing is almost impossible to diagnose over the net.

When you shoot, how is your ejection pattern? 1:00, 3:00, 5:00?
 
The action spring on a carbine should be between 10 1/16" and 11 1/4". If yours is shorter, replace it. If not, that shouldn't be the problem.

Some people say change action springs every 15k rounds. My experience is that they wear out a little before that.


This is the old "bolt-over" malfunction. the cause is most likely a combination of low-power (walmart/wolf/etc) ammo and something in the gas system restricting the flow OR a severe lack of lube, causing the BCG to not go back far enough before it starts coming forward again.
 
Don't worry about the gaps in the rings being aligned. Their being aligned causing malfunctions is a myth. I've intentionally run my ARs on a single gas ring and they ran right.

The AR isn't as finicky or needy as some imply. It's a battle rifle and one that will keep running if you keep up with scheduled maintenance (rings, cam pin, buffer spring, extractor/spring, etc) and keep it lubed properly.
 
with the holes all in the same place.
Click to expand...

what tony said... but the myth is that you need to MISalign them so the holes are in different places. (you don't need to do anything to them.)
 
For those who feel you must clean every 100 rounds there is a pretty good thread.

http://www.m4carbine.net/showthread.php?t=61505
Click to expand...

Thank you Sky

Opened up the action and all friction points are quite dry.
It would be geat if this is the only problem.
Will lubricate now and before next outing and will report back to the forum.

BTW:
Rings were able to hold up the bolt carrier group.

Thanks to all!
 
Last edited:
AR 15's are very finnicky. sp?
they need to be stripped and cleaned often, with very much detail, even to taking the bolt apart. maybe you do need a new part, odds are you arent keeping it wet. ar's run wet.
(very lubed)
Click to expand...

Not true at all. I almost never clean my ARs.

After a class or range trip I lock the bolt back and spray it down with CLP for lube. If it is really easy I will use some Gunscrubber first then spray the CLP.
 
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As for as ARs being finicky, did you guys see that article where a guy lubed his AR with Vagisil to get it back up and running? Of course, he was just making a point, but I think he made it.
 
It would not have occured to me that I should run my XM15 "wet".

It does, however, make a lot of sense that field rifle should be able to be kept up and running with lots of lubricant versus lots of cleaning.
 
I recently had FTF issues with my Bushmaster XM-15. I rotated a number of mil-spec magazines with the standard green followers, but still I had FTF issues. It was suggested that I either use a Mag-pul mag or replace the followers in my mil-spec mags. I bought a couple of the Mag-pul mags and that seems to have fixed the problem.

Next up: I'm going to replace some of my standard followers with the Mag-pul followers to see if those mags work better now.
 
Azizza and I have had this discussion before on another thread. I know of ARs that are rented out and are fired several hundred or maybe more rounds a day sometimes more/less every week.

The poor guns are never cleaned!! I MEAN NEVER CLEANED!!!! No snake the barrel no "NOTHING"!

They come back in from rental and get a couple of shots of Breakfree Clp and that is it.

I know except for those who have seen it first hand that it is hard to believe.

One AR has been used that way for over two years!!

Would I run my personal weapon that way? No way Jose'!

Some new ARs during break in need to get carbon build up under the gas block just to seal the gas system properly. No Kidding....

Whew, people who think u need to run one with fluid dripping off of parts need to change their lube of choice. Just my humble opinion.
 
Meanest thing I've ever done to an AR pattern rifle was turn my M-16 into a SAW at a training event. I went through 280 blank rounds on burst as fast as I could pull the trigger and change magazines (suppressive fire!). In case you don't know, blanks are DIRTY, way dirty. I didn't clean my rifle for the rest of the week, just kept adding lube. It ran just fine, and this was an orphaned TRADOC M-16 with two worn-out gas rings. AR-15's don't need to be clean, they need to be WET.

bushmaster1313 said:
Opened up the action and all friction points are quite dry.
Click to expand...
This is your problem right here. The friction of a dry BCG is slowing the cycle down, causing your bolt-over malfunction. The BCG isn't cycling far enough to strip the round off the mag with the bolt face, and is instead stripping the round with the face of the carrier, under the bolt.
 
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