I recently found an M4 while playing with a Mosin/long range scope/camo spray paint. On initial discovery I was able to pick up the M4 from the heli crash and hold it in my hands with my Mosin on my back.

I then logged out and came back a short time later. When I logged back in I needed to drink so I selected my canteen and like normal my hand carried weapon (M4) fell to my feet. However when I went to pick it up both with the scroll and the Tab inventory I was only able to get the "Inspect" option. I was able to drop my Mosin and then pick the M4 up but then the same issue was found with the Mosin. Relogging with one weapon on the ground allowed me to then pick it up into my hands with a weapon on my back.

This then happened again when I was in firefight a day later and I had to just leave the Mosin after I dropped the M4 to bandage.