Terc;
Sorry I misinterpreted your statement the gauge bottomed out at 4". I just thought you meant it had reached bore diameter. The .070" difference from chamber to bore is fairly constant when they are to nominal sizes. A lot more variation will be found among bore sizes than chamber sizes though. For the 16 gauge nominal is .732" chamber & .662" bore. With the .024":/inch taper you are looking at a cone length approaching 3" in length. This will present no problems with current plastic obturating wads but could not be recommended for use with old type card & filler wads as they would let gas escape around them in the cone
