View Full Version : Armorers and Gunsmiths- HELP!!!
Gentlemen, I have been an armorer on the M16/AR15 platform for many years. I've trained with Colt and Sully and have a fairly good grasp on what makes these rifles tick.
However, I am having an issue with diagnosing a problem rifle. To make it worse it is my personal rifle!
I have a Noveske N4 Light Carbine. The rifle has approximately 5-6000 rounds through it. Until this summer it had bee running flawlessly. In August I arrainged to have the BCG treated with Ion Bond. Springer Precision did the job.
After getting the BCG back and reinstalling it I started to have issues with malfunction. Only occasionally at first but it was still of concern to me as this is my duty rifle.
The rifle was acting like it was short stroking. It would cycle enough to reset the trigger but would not strip off and feed the next round. I would clean and lube and it would clear up for a time.
I checked the gas system for leaks and obstructions and can find nothing. I tried multiple magazines however that made no difference. I thought that perhaps the BCG just needed to be broken in however insead of getting better it has gotten worse. At a recent training event I started the night off by running 3 28 round mags through it. It ran fine. I let the rifle sit for a few hours then picked it up and ran another 15-30 rounds though it. Again, no issues. It sat again for maybe 1/2 hour then went through a 50 round qual course. It malfunctioned during every string of fire. Again, resetting the trigger but not picking up the next round.
I cleaned and lubed it again (Slip2000) for thenext day and tried again. Exact same thing. 3rd night was the same thing again.
I again inspected the gas system and could find no leaks or obstructions. I inspected the buffer, spring and receiver extension and could find nothing.
I ordered a new BCG from Bravo Company. I installed it last night and took it to the range. (this time lubed with Miltec) I duplicated the last courses of fire. Again, the first 3 mags ran fine. I let it cool completely then ran 2 20 round mags through it. It failed to lock open on each empty mag. Again I let it cool then tried to run a full Pmag though it. It began to malfunction again. This time it would start the round out of the mag then the bolt would ride up over the round before it was fed into the chamber. It did this time after time after time.
Tonight I ripped the rifle apart. I removed the gas tube, and stripped the lower. I've inspected all the parts and springs and cannot find a damn thing wrong with the rifle.
I am out of ideas. I had thought that somehow the IonBond treatment (though only 4 microns thick) altered the dimensions enough to effect reliability but that does not seem to be the case. I don't know where else to look.
Any thoughts or ideas would be GREATLY appreciated.
Belmont31R
10-26-09, 05:34
Gentlemen, I have been an armorer on the M16/AR15 platform for many years. I've trained with Colt and Sully and have a fairly good grasp on what makes these rifles tick.
However, I am having an issue with diagnosing a problem rifle. To make it worse it is my personal rifle!
I have a Noveske N4 Light Carbine. The rifle has approximately 5-6000 rounds through it. Until this summer it had bee running flawlessly. In August I arrainged to have the BCG treated with Ion Bond. Springer Precision did the job.
After getting the BCG back and reinstalling it I started to have issues with malfunction. Only occasionally at first but it was still of concern to me as this is my duty rifle.
The rifle was acting like it was short stroking. It would cycle enough to reset the trigger but would not strip off and feed the next round. I would clean and lube and it would clear up for a time.
I checked the gas system for leaks and obstructions and can find nothing. I tried multiple magazines however that made no difference. I thought that perhaps the BCG just needed to be broken in however insead of getting better it has gotten worse. At a recent training event I started the night off by running 3 28 round mags through it. It ran fine. I let the rifle sit for a few hours then picked it up and ran another 15-30 rounds though it. Again, no issues. It sat again for maybe 1/2 hour then went through a 50 round qual course. It malfunctioned during every string of fire. Again, resetting the trigger but not picking up the next round.
I cleaned and lubed it again (Slip2000) for thenext day and tried again. Exact same thing. 3rd night was the same thing again.
I again inspected the gas system and could find no leaks or obstructions. I inspected the buffer, spring and receiver extension and could find nothing.
I ordered a new BCG from Bravo Company. I installed it last night and took it to the range. (this time lubed with Miltec) I duplicated the last courses of fire. Again, the first 3 mags ran fine. I let it cool completely then ran 2 20 round mags through it. It failed to lock open on each empty mag. Again I let it cool then tried to run a full Pmag though it. It began to malfunction again. This time it would start the round out of the mag then the bolt would ride up over the round before it was fed into the chamber. It did this time after time after time.
Tonight I ripped the rifle apart. I removed the gas tube, and stripped the lower. I've inspected all the parts and springs and cannot find a damn thing wrong with the rifle.
I am out of ideas. I had thought that somehow the IonBond treatment (though only 4 microns thick) altered the dimensions enough to effect reliability but that does not seem to be the case. I don't know where else to look.
Any thoughts or ideas would be GREATLY appreciated.
My guess is its short-stroking.
Have you changed the buffer or buffer spring?
Change in ammo? What ammo are you using?
Tried different magazines? PMAGs?
Try a different lower altogether?
I have nothing to add, but it seems you tried to fix something that was not broken and broke it.
I have nothing to add, but it seems you tried to fix something that was not broken and broke it.
That was my initial thought too but it does not seem to be an issue with the bolt.
The buffer is the standard H buffer and stock spring.
Ammunition is a mix of Winchester white box, Remington FMJ and Remington Power Points.
I have tries stock USGI mags, my USGI mags rebuilt with new springs and Magpul followers and Pmags. It is definitely not a mag issue.
I didn't try a different lower. I suppose I should have.
Well if you sent out a new BCG for the ion thing, you could put the old one in and see easy. If all you changed was the BCG, two of them it seems, what could have happened with the lower?
The first variable was ionbonding the BCG.
You've already tried another BCG, so that variable has been checked.
How much tension do the gas rings have? With the bolt installed into the carrier, how much resistance is there when you move the bolt back and forth.
Are you sure the roll pin in the buffer isn't drifting out?
Are you sure the bolts securing the key to the carrier haven't loosened?
If the above things are all OK, I would consider using a new buffer spring and new gas tube.
Is the CH bent? I had one bend quite a bit before I noticed it, and the key was dragging on it.
Keep us posted!
Here is what I would do.
1. Check to ensure that the bolt carrier keys are tightened and look for obvious signs of gas leakage.
2. Check your gas rings. To do this using a clean(ed) bolt carrier group completely assembled extend the bolt away from the carrier. Stand it on its' head (bolt face) and see if it collapses under the weight of the carrier. If it does then your rings are bad.
3. Consider replacing the gas tube and then run the gun with ammo that is known to work along with good mags.
4. How did you inspect the buffer spring? You have to measure it to know if it is within specs or not.
5. Try a standard carbine buffer. Not and H or H2.
Jaeger, this is driving me nuts trying to think what your issue is so I guess you are really pulling your hair out. The issues that come to mind are these. Your gun runs good for several mags. So it really can't be a gas issue. I am leading in the direction of heat. Your gun runs for about 90 to 100 rounds and then starts "short stroking". Things expand with heat as we all know. In an AR platform there are many different metals inside and they all will expand at different times so I would first look at the lighter metals. Is the BCG heating up something small like the receiver extension detent? Is that hanging up on the bolt carrier and slowing it down? Did the zero fail on the BCG leave a residue in the upper receiver and is that residue heating up and slowing the bolt carrier down? Is the charging handle bent? (didn't think of that one) My suggestion is to give your rifle a good cleaning and see if there is anything that hangs around in there after you have cleaned it up. Then inspect all the parts. Good luck brother!
Here is what I would do.
2. Check your gas rings. To do this using a clean(ed) bolt carrier group completely assembled extend the bolt away from the carrier. Stand it on its' head (bolt face) and see if it collapses under the weight of the carrier. If it does then your rings are bad.
IG,
I know you’ve attended numerous AR15/M16 armorers courses. Regarding the “Table-Top” gas ring serviceability check. Do you have anything published from a course that outlines this method of inspection?
I see this method of gas ring inspection referenced often, but personally have never seen anything in writing.
The first variable was ionbonding the BCG.
You've already tried another BCG, so that variable has been checked.
How much tension do the gas rings have? With the bolt installed into the carrier, how much resistance is there when you move the bolt back and forth.
Are you sure the roll pin in the buffer isn't drifting out?
Are you sure the bolts securing the key to the carrier haven't loosened?
If the above things are all OK, I would consider using a new buffer spring and new gas tube.
Is the CH bent? I had one bend quite a bit before I noticed it, and the key was dragging on it.
Keep us posted!
The gas rings on both the Ionbonded bolt and the BCM bolt are new and have plenty of tension
The roll pin on the buffer is fine.
The gas key on both bolt carriers is fine.
I looked at the charging handle and couldn't see any bends,deformations or unusual wear.
I'll finish cleaning every nook and cranny, replace the gas tube and buffer spring. Maybe even a new Charging handle and I'll try it again.
I don't know. I'm grasping at straws right now.
I'll finish cleaning every nook and cranny, replace the gas tube and buffer spring. Maybe even a new Charging handle and I'll try it again.
I don't know. I'm grasping at straws right now.
You mention replacing the gas tube. Have you checked the gas tube to carrier key fit? Does the gas tube need to be adjusted?
ETA: Gas Tube Adjustment and Buffer Spring inspections: http://http://www.weaponevolution.com/forum/showthread.php?t=1613 (http://www.weaponevolution.com/forum/showthread.php?t=1613)
Might want to check the torque/alignment on the barrel extension. I have seen them out of whack or shift over time from improper torque / install. This causes a misalginment in the feed ramps and can cause what you are describing. Not that common but I have seen it happen. The misalignment of the feed ramps can be ever so slight and hard to notice.
Trigger?
I have seen a few two stage triggers drag on the bolt carrier if the trigger was held to the rear.
I have also seen the top of a carrier key bolt break off but it's held in place by the staking. Two carriers seems unlikely though.
Todd,
Good point about the trigger. I have seen that once or twice myself.
Trigger?
I have seen a few two stage triggers drag on the bolt carrier if the trigger was held to the rear.
I have also seen the top of a carrier key bolt break off but it's held in place by the staking. Two carriers seems unlikely though.
You might check for debris possible blown primer in gas key causing a partial blockage that closes key after it heats up. If negative there I'd check for
blockage at gas port..Also try Full Mill-spec ammo lower preasure 223 causes
problems in 5.56 gas system..
Blankwaffe
10-26-09, 21:45
I assume you have checked the tension on the mag catch and the mags are staying where they should in use.
Had a similar issue after a friend "fingered" one of my rifles.
The gas system is clear all the way through. Tube/key alignment seemed fine but I'm wondering if the end of the hasn't worn enough to cause some blow by. I've seen that once before but the wear was visable and apparent. I'll have to reexamine the trigger group As well.
Thanks for all the input so far. It helps to have some fresh
minds involved.
Check for a worn bell on the gas tube. If it is worn off, then you are leaking gas, resulting in short stroking. You are always welcome to send it to us if you wish to have it diagnosed.
A worn bell on the gas tube seems to have been the issue.
I fully stripped the rifle last week and pulled out the gas tube. The wear was more apparent when I removed the tube from the receiver.
I got a new tube from Bravo Company and installed it yesterday. (after taking the opportunity to clean every nook and cranny)
I took it to the range this evening and ran several hundred rounds through it without a hitch. It ran hot, cold, clean and dirty. I had to use the BCM bolt group since I left the Ionbonded group at home. :mad:
I will reinstall the Ionbonded group tomorrow and run the test again. I am fully confident that it will run perfectly.
I'm still curious as to why the malfunctions only started to occur after having the bcg done up but I suppose they would have started no matter what. I'm just glad my friend is fighting fit again.
Thanks for all the help guys.
A worn bell on the gas tube seems to have been the issue.
Did you follow the gas tube adjustment procedure in my link above? If not, it might not be long until the new gas tube wears down as well.
IM sent.
I'm still curious as to why the malfunctions only started to occur after having the bcg done up but I suppose they would have started no matter what.
It could be that the gas tube was just to the point of failure, before you had the Ion Bond applied. And would have failed shortly after whether the bolt was a standard bolt or the bolt with Ion Bond applied.
I’m not familiar with Ion Bond. Is it harder than chrome? Could the Ion Bond applied to the interior of the carrier key accelerated the wear that was already started?
eddymunster
11-04-09, 15:08
Nice to see ya Quib. I can get educated again.
Nice to see ya Quib. I can get educated again.
Thanks. Good to see ya' posting here as well.
There are lots of good folks at M4C, folks we can all learn from. :)
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