In the last few months I have seen advertisements touting the benefits of polishing the internal parts of gas guns, particularly Berettas, in order to “improve reliability.” Likewise, I have seen other advertisements for barrel polishing in order to increase velocity (perhaps by reducing friction). Are either of these modifications a legitimate use of barrel polishing?
Polishing the internal parts of guns, particularly pistols such as the 1911, has been accepted gunsmith practice for a long time. The main advantage to polishing the moving parts of your semi-automatic shotgun (such as the 303) is not really to make the gun function more smoothly. It is to remove the tiny burrs on the parts which provide the beginning points for metal fatigue cracks. Polished parts do not break as often. The Beretta 303, 390 and 391s are exceptionally reliable guns with very little parts breakage. It is questionable whether polishing up the interior parts like the action rod and lifter mechanism will improve things, but it would not hurt.
Polishing the interior of the barrel may increase velocity very slightly, but I doubt if the increase would exceed the normal shell to shell velocity variation of commercial shotshells. Proper polishing of a barrel may reduce barrel leading and fouling to some extent. The barrels of the Berettas (the 303, 390, 391s and all the O/Us) are chromed and polishing will have no effect. Most modern shotgun barrel machinery produces factory barrels that are quite smooth.
Proper barrel polishing is not as simple as it sounds. The American and English usually polish in a rotary fashion, much like chucking a cleaning rod into an electric drill and having at it. This makes the microscopic scratches of the polishing go in a circular fashion, at right angles to the shot charge going up the barrel. Not ideal. The French polish by setting up their machines to push in and out the barrel, in line with the bore. This is more time consuming and requires different machinery, but it does put the micro scratches in line with the shot charge and results in a barrel less likely to foul.
Shotgun Report’s Technoid