I have Sako A7 .300 WM. Ever since I bought it, I've had problems with the cartridges prematurely popping out of the mag will laying untouched, while locking the mag into the rifle and when cycling spent/new cartridge through the action. I previously contacted Sako/Beretta support about this problem and they sent me a new factory magazine. The same symptoms persist even with the new mag. At this time, I can't trust this Sako rifle/magazine to hunt with (elk). I've had the same thing happen in while hunting. So, it's a serious dependability problem. (link to a youtube video I made to demo the problem.)
http://www.youtube.com/watch?v=rPnNMmsIsgg
I have another Sako A7 .270 Win and 2 Tikka rifles (.30-06 and .300 WM) that never has problem like this.
I have to think the .300 WM magazine is underdesigned (e.g. too thin/flexible mag walls for the pressure of the spring/.300 WM cartridge.) What can be done to resolve this problem, besides waiting for aftermarket all steel heavier gauge mag to replace?