I suspect the barrel wants to jump forward a little as recoil makes the breech bubp against the end of the channel. Bed it there for sure, and in the tang bolt hole. Apply shoe polish with a toothbrush to the steel and allow it to dry before you drop the barrel back into the channel, and the tang bolt into it's hole. Be sure to apply the wax to the trigger plate where the bolt will thread into the plate, otherwise, you can end up with a one-piece pistol. Apply bedding to the ends of the tennon inlets in the barrel channel too, and that'll keep the barrel from moving fore and aft'. Allow the AcraGlas to cure until the puddle that is left over is hard. Place a brass rod into the bore, remove the barrel slides and the tang bolt, and gripping the forestock and the pistol grip, crack the brass rod on a bench top to start separating the metal from the wood. It'll be tight, and require a good wrap. Be sure there is no bedding compound overlapping the metal and wood...otherwise you can take chunks out of the wood, if the compound adheres to the steel.
And on your next build, don't leave gaps around inlet parts for "clearance". Make your wood to metal as close as you can.