The Yugo mausers are known to be "tight".
To help with feeding, take the bolt out of the rifle and remove the claw extractor. Take a stone and smooth out the bottom edge of the inner face. Go slow, you aren't trying to really remove a whole lot of material, just smooth it out and reprofile the edge so that it snags the cartridge rim positively.
Go slow, take your time.
Machine guns are awesome until you have to carry one.