If have this issue, my 3rd character would need Granatgevär m/49.
And before everyone jumps in to quote weapons location guides. I have collected those places on my first play trough, and thrown away all the previous version. There was no plundra available then.
So my question is, Is my only hope to get Granetgevär m/49 as loot drop from weapons box or robot?
Hi,
Do you mean you have already been looting all regular places? For example the military airfield and some of the “Beredskapsförråd” often have the GRG.
Yes, and sadly with my 2nd character with 2nd play through with my friend. Made a mistake and didn’t store Granatgevär m/49, even i got special as drop from tank. Trashed exceptional one. 
Unless those small weapons cache building, which can be found outside and inside some bunkers have greater chance to spawn one, those i haven’t checked yet.
I was hoping quick and dirty way to obtain one, but seems i might be out of luck.
Edit:
After typed this initial reply, start game. Checked first weapons cache outside. What you know, thee m/49 inside. Quality worn, but does the job for now. 
It took less than 15min to find one.