There are slotted wdges, having a slot cut up the middle. You remove the barrel and start the wedge through the escrutcheon into the barrel channel just enough to put a brad through the slot inside wedge recess, but out of the way for the barrel so even if it gets loose, it can't fall completely out. Sometimes just putting a cleaning patch in the barrel channel under the barrel keeps enough tension on the wedge to keep it in place. Frankly bending the wedge doesn't work all that well. If you can flip the barrel over on a piece of wood with a clean rag to prevent marring the finish and use a punch to give the bottom of the tennon a slight bend upward in the middle. I said slight, like a hundredth of an inch at a time. Don't mash it with a six pound sledge.
Tap the underlug down a little bit at a time and keep testing until it's just a snug fit. If you use a couple of different barrels on the same stock make each barrels underlug the right fit instead of bending the wedge which will require a seperate wedge for each barrel. It's a whole bunch easier to get out than a bent wedge as well.