I have a PF-9 that is acting up on reassembly. I will have the slide assembled and slide it onto the rails of the frame. When I draw the slide to the rear, to insert the take down pin, the barrel goes back with the slide. the best i have gotten it, was with the barrel in a half open position with the slide all the way back. I am either inserting the take down pin in front of the locking bar, or the locking bar is blocking the hole because it traveled back. Either way, the barrel is not in the proper place for reassembly. Please help.