Magazine Woes (X Bolt)

[firepower 68]

I have a Browning X Bolt in .223 and have to say that it is the favourite out of all of my rifles by far. There is however a but... I have put less than a thousand rounds through it and I have noticed a serious fault with the magazine. I knocked up a hundred rounds using brand new Lapua match brass with FMJs to fire form them for an upcoming fun shoot. I loaded the magazine and when I went to cycle the bolt the round jumped out of the mag and wouldn't chamber. After trying a half dozen different rounds the problem persisted. I ended up using the rifle as a single shot for the day. I thought it over and it occurred to me that apart from the odd box of factory rounds all the ammo that has gone through it has all been fire formed. These cases are fractionally bigger in diameter than the factory ammo. I have a hundred rounds of loaded fire formed Lapua match kicking about so when I went out the other night foxing I took them as usual. First charlie of the night trotted off into the darkness as the rounds all jumped the lip of the magazine. Pissed off, you can't even imagine. Has anyone else experienced a mag wearing out so fast?