I have been reading a couple of PMs and threads in the forums that people are asking if non-gms can loot a M4. Adminpwn did announce that non-gms CAN loot level 100 gears, but what he actually meant is that non-gms can only loot up to Elite Gears. The M4 is classified as a legendary weapon, not an Elite weapon.

So M4s are not lootable for non-gms.
There is also no proof or evidence of screenshot of any non-gms looting a M4 up till now, so that also meant non-gms cannot loot a M4.