Round won't chamber when charging with handle, but load with bolt release?

AR/M4 AR Technical Discussion
1

Guys,

Apologies for the brevity of my post and the lack of pictures in advance.

I’ve an AR that I’ve put about 200 rounds through and run into this problem on occasion (it happened again this weekend).

What doesn’t work: If I insert a mag on a closed bolt, a round will not chamber when I charge back with the charging handle. The bolt/carrier will either glide over the magazine or half-ass chamber the round and get the case caught halfway out of the mag.

What works: If I lock the bolt carrier back manually with an empty magwell, insert the mag, and then use the bolt release, the rounds chamber just fine.

What might be causing this?

Mods, if this is wrong subforum, let me know.

Thanks.

2

If the mag is inserted on an open bolt, then charging handle pulled, does it work? What about a half loaded mag?

Sounds like either a mag issue or you are not seating the mags all the way on a closed bolt, which is easy to do.

3

I’ve had the same problem, usually on a closed bolt I really have to get that mag in good

4

I have not thought to try this variation. When it happens again, I’ll check that.

Had it happen on both full 20 round mags and half-loaded ones.

I’ve got Lancer mags and a single Colt metal magazine, and it’s occurred with both types.

I thought it was simply not seating the mags properly, but even when I double check that, I still have this problem.

5

Are you riding the handle / bolt carrier forward?

6

Are you riding the charging handle forward when trying to charge the rifle? Should just pull it to the rear and let fly, riding it forward can cause issues when chambering a round. Now, if the issue continues then I am at a loss without seeing the platform.

The BCG gliding over the top just sounds like the magazine is not seated fully.

7

Try this-
-With the bolt closed, insert the mag. Push pull to ensure it’s seated properly.
-Pull the bolt back and lock it to the rear.
-Push the charging handle forward and lock it in place.
-Hit the bolt release.

What we’re looking for is whether or not the charging handle is creating extra drag, if the bolt being dragged over the top round is somehow displacing it, or if the action spring is starting to fail and the extra normal drag & weight is causing the failure

8

Thanks for the input, guys. I posted this before going out of state for the weekend.

I will report back after testing what you all have suggested tomorrow evening.