Hey guys, I was at a shoot this weekend and noticed that two of my magazines (all USGI magazines) would not insert in my rifle when loaded with 30 rounds.  I never noticed this simply because when at the range, I usually leave the bolt locked open between magazines, and load them on an open bolt.  I did not try the magazine when it was empty, but would assume that the feed lips are out of spec.  

This is how I discovered the problem...I loaded the mag with the bolt open.  Closed the bolt, and fired a few rounds.  Had a FTF, and a stuck case.  Ejected the mag, cleared the rifle, and tried to load it on a closed bolt. The magazine would not insert.  Thats basically how I discovered the problem.  Had another FTF and tried again.  Same problem.

No problems with any other magazines that I used at the range.  

What could be the problem?  Out of spec feed lips perhaps?  I figured it would take quite a deformity to do this...one that I could see easily, but the magazine "looked" fine.

Any ideas?

What you describe is not uncommon and varies from rifle to rifle and mag to mag.  It is likely it would seat with a good smack, but I've seen some go in so tight this way that operation is compromised.

You've discovered the reason why most tactical shooting schools recommend only loading 28 rounds into a mag.

Another tip? Try pulling the charging handle back, locking it there, then inserting the mag. Of course,while keeping the muzzle downrange, FCS on safe, etc, etc..

Meplat-