I have been looting heli crashes since the new update came out on stable branch but I haven't found any M4s so far and nor had my friends. We checked more than 50 heli crashes.
We found attachments for the gun, mags, even the new black skull balaclava and a box of ammo.
Things that should spawn but it doesn't happen:
- M4 rifle
- smersh vest
The gun is either 1/75-100 servers or this is a bug and the weapon doesn't spawn anymore.