I have one newly built rifle, bushmaster lower no name upper I think it came from model 1. Any way the loaded clip wouldn't lock in unless the bolt was back.  After opening and closing the upper with the mag in place, it now locks in with loaded or unloaded mags. I bought a beta C mag and it won't lock in unless I pull the bolt back. I opened and closed the upper with the mag in place, and now it clicks in fine.  Should I shoot it like this?  I just don't  want to ruin an expensive magazine. Thanks

Quoted: I have one newly built rifle, bushmaster lower no name upper I think it came from model 1. Any way the loaded clip magazine wouldn't lock in unless the bolt was back.  After opening and closing the upper with the mag in place, it now locks in with loaded or unloaded mags. I bought a beta C mag and it won't lock in unless I pull the bolt back. I opened and closed the upper with the mag in place, and now it clicks in fine.  Should I shoot it like this?  I just don't  want to ruin an expensive magazine. Thanks

You may need to adjust your mag catch properly.

There's usually a bit of tension when inserting a fully loaded magazine with the bolt closed, the rounds must be compressed down into the magazine slightly inorder to fully seat/lock the magazine into place.

A bit of a "pop" should be delivered to the base of the loaded magazine driving it into position when the bolt is closed inorder to properly lock it in place.

Definitely a different operation or feel to locking the magazine in place than if the bolt is locked back and held in place by the bolt catch.


This is a question often asked by first time AR15 owners and doesn't neccesarily suggest anything is wrong with the rifle.    However if you are already an AR15 owner and this new rifle is being more problematic than with other AR15s that you have experience with, perhaps there is something a bit out of spec.

First, I would try loading an empty magazine into the rifle with the bolt both open and closed.   If that tension disappears then it's likely that you are feeling the rounds being compressed into the magazine while trying to load with the bolt closed.

The lower is a factory built Bushmaster.  I shot it with a 30rd magazine and it seemed to work fine, didn't hurt the feed lips on the mag. any. I just don't want to ruin the lips on a beta C. I noticed the Beta has the fake rounds used as  the follower. I think that is why it feels harder to insert with the mag empty.

Unload about 2 rounds from that mag and try it again.

After inserting and removing the Beta C a few times it seems to click in fine. I think that the plastic just needed a little help as described above.  I was being to careful, never had a $240.00 dollar mag before. Thanks

Just try loading a full magazine from an already open bolt. Much easier, not that it is that difficult.

Quoted: Unload about 2 rounds from that mag and try it again.

what coastie said....that'll take care of it