I was in muiltiplayer the other night and someone had a m/49 that did rapidfire (more than 2 rounds).
I have EXP m49 and it doesnt do this? Is this an attachment? Somehting that can be crafted?
They are either using a bug/exploit, or a mod. So under normal gameplay there is now way to do that.
I have seen people do it before. Definitely not something you should be able to do regularly.
I would say if it was anymore than 4 then it’s hack because they could have 2 exp m/49’s and swapped to it quick
As said above, it most likely was cheater. Though, talks of game cheats isn’t allowed here and with question answered, i’ll lock the topic. 
//Mod