Raiders used whatever they could get, and often that would be the massive amount of cheep civilian guns that littered the wasteland, or the even worse scrap built guns they would throw together. But a gun is a gun, and even if a raider is a bad shot, they only need one lucky shot to take out a pony, so they just fire as many bullets as possible until one hits.

Most raiders start out as just petty thieves, relying on intimidation to get what they want. and it was not uncommon for them to use empty guns to make a threat, hoping the other pony dose not call their bluff. But as their chem additions get worse, the less the bluffed, and the more they are willing to beat a pony to death with their gun, even if it's loaded.