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Discussion Starter #1
Hello everyone I have a mysterious problem with my ar15: after 1000 shots without issues, now it fails to catch the bolt completely open after the last round is shooted.
1-If I hold pulled the bolt catch and i shoot the last round it works properly and the bolt stay open correctly.
2-The magazines are the Brownells steel ones.
3-The ammunition: Swiss army ordinance Gp90 5,56x45 63 gr, Barnaul 5,56x45 62 and 55 gr.

Here in switzerland no gunsmith has experience with the ar15 rifle.
Someone could give me a valid advice?
 

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It sounds as though it might be short stroking, meaning that the gas charge is not sending the bolt carrier back far enough to give the catch time to engage it properly. I'd clean and lube the rifle thoroughly, especially the bolt and carrier, and check the gas rings while you're at it. Also, double check to verify that your bolt catch is functioning properly, and, you might try some different mags to see if the followers are not pushing the catch up far enough. if you have access to some hotter ammo try that to see if the problem goes away.
 

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Mags with a weak spring can cause this as can the spring that pushes the bolt catch into position.
Check the Mags first and than make sure the Bolt catch is free.
What brand is the AR?
 

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Pull that bolt out, . . . spray it down with some solvent and give it a scrubbing.

Drop out the tee handle also, . . . scrub it.

Put some oil on it, . . . put it back in.

That should take care of the problem.

May God bless,
Dwight
 

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Clean...scrub...scub...clean! Lube...lube...lube and then...lube some more...

If it closes?...run it 'till it smokes...
 

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Discussion Starter #7
Hello thank you guys for all your answers!

-The rifle is accurately clean and lubricated and every magazine i have push up the bolt catch very strongly.
-I tried shooting the Swiss army ammunition GP90 that is very powerful.
-If I insert an empty mag and I pull back the bolt it stops.
-I don't think is a short stroking because if I hold pulled the bolt catch with my hand and I shoot, bolt stops open correctly.
 

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I would check the bolt catch for chipping or other damage. Also try replacing the bolt catch spring.
 

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Could be a number of problems. First thing I would do is load a single round in your magazine and fire your weapon. If the bolt locks to the rear it is gtg. If it doesn't then it could be short stroking, a mag problem, bad ammo, rough (dirty chamber), or a problem with your bolt catch. If it turns out to be short stroking I would first check to see if the gas key is properly staked, then test your gas rings. This can be done by removing your bolt and carrier. Extend the bolt and place the whole assemply vertical on a flat serface. The bolt rings should have enough contact to support the weight of the assembly without collapsing. Let us know what you find.By the way what is your barrel length?
 

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Far out possibility, but those gas rings* act as piston rings do in an automobile engine, sort of anyway, and if yours has the three rings, note if the break/notch of all three are lined up, they should not be, but opposite of each one; hence, no extra leakage. Some argue that a 15 should be operated "dry" but find that is not the case, operate them well oiled, other than the bolt face. Might mention that you can "tighten" the spring pressure on the bolt catch/release by pushing the button far to the left side, rotate the piece protruding, and turn it a notch or two see if that helps, just a thought.

*May not be available to you, but there is a 1 piece gas ring offered to eliminate the possible leakage problem mentioned above. Google Brownells for possible source???
 

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If the bolt locks back manually on an empty magazine, but doesn't do it when firing, then the bolt is most likely not coming back far enough.

You may need to scrub out your gas tube with a pipe cleaner.
 

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Make sure the buffer plug/end cap isn't working it's way out of the buffer. Some are not pinned to the body of the buffer and can come out over time and prevent the bolt carrier group to cycle the full distance. It's just one possibility.
 

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Might mention that you can "tighten" the spring pressure on the bolt catch/release by pushing the button far to the left side, rotate the piece protruding, and turn it a notch or two see if that helps, just a thought.
Not familiar with the M-4 but that sounds like your tightening/loosening the magazine catch. You can adjust the tension on the mag release to have them spring out harder. Took more effort to push the mag release when you did change mags. Too little tension and you couldn't tell if the mag was locked in. That's what I remember from the A-1's that we used. Don't remember an adjustment on the bolt catch. Please correct me if I'm wrong. -Lloyd BEERCHUG1
 
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