In answer to your postscriptive advice to the misguided among me, Wonko, bore size does have one tiny thing to do with stuck plastic wads. It is more probable that one will stick in a .723 bore than in say a .742 bore. Primer alone is frequently sufficient to cause wad and shot to exit the bore of an overbored target gun and frequently not sufficient to do so in a sub-.729 bore. Obviously, lack of propellant force to overcome inertia is the major cause; perhaps less obviously insufficient propellant force to overcome a tight fit of wad to bore. Friction also contributes to sticktion. If this ain't so, I welcome correction but in the meantime will follow most excellent advice and put powder in at least some of my shells.

jack