4070 SS

[desert deuce]

Moreover, what Bruce Molds is implying and I am saying is that the groove diameter of the barrel is always a larger number than the bore diameter.

A .410 Bore would have something like a .414-416" groove, more or less.

If, as cartridges of the world states, the rifle was originally rifled to take a .403" bullet the bore diameter was probably less than .400" when the rifle left the factory and the fact that you are able to chamber a cartridge with a .410" bullet implies the rifle has been altered as Bruce surmises.

Again, for your safety and the longevity of the rifle it is wise to determine the actual dimensions of your rifle before further loading for it, especially if you plan on shooting it very much.