Ar15 bolt going home when you bump stock

Zbizzle911

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My brother assembled an ar15 from aero parts. Everything looks fine but when the bolt is locked to the rear and you barley bump the stock it send the bolt home. None of mine do that. Any advice on what to check? He’s an newb and I wasn’t there when he put it together.


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Have to see it. Bolt catch is only thing that holds it back. May be outta spec like above, might be the little piece missing behind the spring not keeping tension. I’d like to know what you find out. Where’s your BIL at?
 
Have to see it. Bolt catch is only thing that holds it back. May be outta spec like above, might be the little piece missing behind the spring not keeping tension. I’d like to know what you find out. Where’s your BIL at?
He's in Midway too. I told him to buy a new Bolt catch bc thats all I could think of too. Ill make sure he gets one and i'll let y'all know.
 
Inspect the bolt catch, make sure the spring is installed and proper, and make sure it can move freely.
 
Is it a fixed stock or collapsible?

I had this happen on a fixed-stock. I had used a hardware-store screw to attach the stock to the buffer tube. The screw was just a tad too long, and touched the buffer when the bolt was back.

Just enough to set the bolt-lock on a hair trigger. But not enough to cause jams when firing.
adjustable
 
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Perhaps the catch is binding on the roll pin. If the holes weren't aligned and the roll pin hit the edge of the hole in the catch, displaced metal would rub against the pin.
 
On mine when...
Empty mag in, BCG open, butt strike, BCG stays open.
BCG locked open, no mag, butt stike, it depends if the strike is hard enough to cause the BCG to shift rearward enabling the catch to retract by the spring force.

It really doesn't take a lot of force to move the BCG slightly rearward to let the mag catch spring drop the catch.

Maybe the catch isn't up as far as it should. @kcult @Me. might be on it. Is the catch easy moved to the extreme up position?
 
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I had a factory gun with a bad bolt catch that had to be replaced to get it to work properly. The spring was too strong or the catch was out of spec, I forget which. I replaced the spring and catch and have not had a problem since. If you have another AR 15 that works properly, temporarily swap out the parts with the bad ones to see what is causing the problem.
 
Had this problem. Replaced with Seekins.
Works great now.
 
Get an empty magazine, take the upper off the lower, insert the empty magazine, and observe how the catch works. The bolt catch barely moved on the one I have that did not work properly.
 
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I bought a San Tan Tactical set that would do this. It was due to the milling at the takedown pins. The “slop” would allow it to release the BCG. They happily replaced it when they seen what it did. You could twist the upper and lower and it would do it occasional too.
 
If it’s releasing with only a tiny tap that’s not normal. But I haven’t handled an M4 or M16 I can’t slam my hand against the stock to get the bolt to close if it’s locked back.
 
If it’s releasing with only a tiny tap that’s not normal. But I haven’t handled an M4 or M16 I can’t slam my hand against the stock to get the bolt to close if it’s locked back.
my buddy in WRC said that's how they TRAIN them to release the bolt on their patrol rifles
 
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