Bolt wont stay open on final round (AR 15)

[stagpanther]

That's why I think your issue likely lies in the catch function.

Let me word this another way--if you pull the handle back "just enough" to get the catch to engage the bolt and hold it back--and then give the side of the receiver a slap with your hand or thump the gun on it's buttpad--does the bolt/carrier sometimes release without having to press the bolt catch lever?

[PushPuller]

Let me word this another way--if you pull the handle back "just enough" to get the catch to engage the bolt and hold it back--and then give the side of the receiver a slap with your hand or thump the gun on it's buttpad--does the bolt/carrier sometimes release without having to press the bolt catch lever?

Nope. Once its actually locked back it will stay unless the release is engaged.

[marine6680]

Tip the muzzle down and it will catch?

I am confused.


Remove the upper from the lower. Try to move the bolt catch. It should move easily, but with noticeable spring pressure that wants to keep the catch in the down position. There should not be much play front to rear or side to side, it should rotate on the pin. It should not flop around on it's own when you move the lower around or turn it upside down.

With the upper still off the lower, insert an empty magazine. The follower should push up on the bolt catch and raise it fully.

If the bolt catch is out of spec and stiff, the magazine may not be able to lift it fully. Or if there is a bunch of crud in the bolt catch channel it can make movement stiff as well.

If you see no issues in the above checks... Put the upper back on the lower.

Next, push the bottom of the bolt catch lever with your thumb and then pull the charging handle rearward. You do not or should not need to yank on that handle very hard. Moderate effort is enough... If you have to yank on the handle almost like your life depends on it for it to work... Then there is an issue somewhere making the BCG movement stiff,and that will cause the issue you are having.

If everything seems fine with the above... Then it is likely a gas issue.

[PushPuller]

Remove the upper from the lower. Try to move the bolt catch. It should move easily, but with noticeable spring pressure that wants to keep the catch in the down position. There should not be much play front to rear or side to side, it should rotate on the pin. It should not flop around on it's own when you move the lower around or turn it upside down.

Spring pressure feels fine and comparable to my other ARs. The bolt catch does have play front to rear. Not enough to flop per se, but it does move slightly.

With that being said I think a new bolt catch is in order.