duncan61 wrote:I have looked it up and the zipper is based of the 30/30 case which is .506 inch and the 303 is .540 I am no expert but I thought the barrel was chambered and screwed in to the receiver and headspaced on the rim
Well firstly the rim size is of little relevance.
What is important is the base diameter which in the case of the zipper etc. is 0.422".
The barrel tenon on a Cadet is 0.750 x 14 TPI so that will make the minor diameter approximately 0.60".
So that then leaves an effective wall thickness over that part of the chamber of (0.6 - 0.422) / 2 = 0.089"
Not very thick and certainly not enough, in my opinion, to contain a cartridge with a maximum chamber pressure of 42 000 PSI.