Whenever I holster my rifles and/or any two-handed weapons, they are holstered upside down like when wearing Power Armor in Fallout 3. Even when I'm not wearing ANY armor, it just holsters like that. Pistols are no problem, and I first I thought it was normal, because I didn't use any rifles until I had the NCR patrol armor, which I saw had my assault carbine hosltered upside down. Then, same with the service rifle. I knew it shouldn't be like that because prior to that moment, I had seen NCR troops with service rifle holstered regularly.

Nevermind, as soon as I restarted the game, it was normal again.