Recently I've noticed that AKM mags are a lot more common in barracks than AK101 and AK74 ones. I think this is because while each mag has an equal chance of spawning, there are more variations of the AKM mags (m_akm_palm30_black, m_akm_palm30_green and m_akm_30rnd, as well as the drum mag), whereas the other AKs only have one mag variant. This means for every 6 magazines you find in a barrack it's likely to be 3 30rnd AKM mags, an AKM drum mag, 1 AK101 mag and 1 AK74 mag. In the last week I've found 8 30rnd AKM mags, 1 drum mag, 2 AK101 mags and 1 AK74 mag which illustrates the issue. I think the mags for each gun should spawn at the same rate so you are equally likely to find an AKM mag or AK101 mag (which seem to be non-existent tbh).

Thanks