Captured enemy weapons are often booby trapped. Soldiers either learn that the hard way, or pay attention when their more experienced leaders warn them, not to pick up anything you didnt drop. But some captured enemy weapons are collected for study (of how they operate, how much use they have gotten, how well the enemy was taking care of them or for training.) In Iraq, U.S. Air Force special operations ordnance (weapons) experts collected a Russian made Dragunov SVD 7.62mm sniper rifle that had been abandoned . The air force was planning to check out the weapon, and then use it for training. But first they test fired it in a safe manner (secured it to a work bench and pulled the trigger remotely with a wire attached to the trigger.) When fired, the rifle blew apart. It turned out that someone had taken the rifle apart (as you would for cleaning) and then drilled a three millimeter hole in the barrel just forward of the chamber (where the cartridge goes, and is fired from.) This allowed hot gasses to escape through the hole and blow apart the wooden stock. Anyone firing the weapon in that condition would have suffered severe damage to at least their hand, if not eye, face and head. Examination of other weapons found in Iraq revealed at least one other rifle with the same booby trap modification. Someone had probably drilled that three millimeter hole in many weapons. Since Iraqis have picked up a lot of the weapons left behind by the fleeing Iraqi army, Iraqis will most likely be the only ones injured by this particular tactic. But maybe not. On further investigation, it was noted that the "modified" rifles were marked, in Arabic, with the text; "Do not fire, training only." Apparently, the Iraqis had made sure that weapons selected for just non-firing training should be modified so that if anyone tried to fire it, they would be killed or injured. That's one way to get the troops to pay attention.
American military personnel are forbidden to collect weapons from the battlefield as souvenirs.