So you can indeed change the firemode of your gun.

[MarczXD320 171]

I discovered this by accident, sometimes when i press the D-pad to open the quick equip menu it doesn't open at all, so i keep pressing until it does, that's when i discovered this, there's quite a few youtubers (soyLEGEND and kamz 25) who also discovered this so i wasn't the first xD (by the way their videos are very helpful)

The firemode in the xbox one version is broken right now, that's because it hasn't a key to change it, but there's a small flaw that allow it.

What you want do do is aim the gun with LT and spam the right D-pad button repeatedly, the firemode will be changed from FullAuto to SemiAuto depending on the gun.