take a square of hardwood ... about 2"x2"x1" in the center, drill a hole clear through a bit larger than the small end of the fpj, then drill a hole into that one about 1/4" deep that is slightly bigger than the larger end of the fpj.
Place 209 primer on flat, smooth surface, align fpg on primer, push on snug using small center hole in block of wood. To remove, insert larger end of fpj into larger hole and tap out spent primer with a punch or small dowel of the right size. You could get real creative and devise a little stand for the block of wood so you wouldn't need to empty the spent primer each time.
Or, just pitch 'em and buy new ones.