I believe that this has something to do with the new mechanics you guys are implementing for weapons. But please, do some testing for the mag-fed weapons.
It is highly bothersome for something like this to happen. I will have you know that at the moment, the AK-74 mags are rarer than a SVD, VSS or any other fancy gun.
(I have seen upward of 7 SVDs and just 3 AK-74 mags in Experimental)