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2152hq,

Thank you for the contact information for David. He and I have had two very good and informative discussions. He did, in fact, build a 7X57R DR Winchester 21 and it did fail by partially opening. He eventually stopped the project. Our discussions have caused me to reconsider the design of the receiver for greater pressure shells. Neither of us believe there is any problem with the 45-70 I am current building but I had intended to follow that shortly with a 6.5X57R. Unfortunately that cartridge is in the same pressure range as David's. So, I must either stay with lower pressure rounds or make design modifications. First let me say that in previous posts I have stated pretty confidently that 45K psi and below should not be a problem and it may not but I am now not so sure. The 7X57R is about 50K so not that far away. Until I know more please take my earlier statements as possbily too optimistic.

There is one difference in my receiver and his. He had an original Win. 21 20 ga and mine will be 4340 alloy with much higher yield and tensile strength hardened appropriately. His failure mode was most likely from elastic deformation allowing the barrels to pivot on the hinge pin enough to partially unlock. He did not experience plastic deformation though i.e. no permanent change in dimensions. So, I should experience less deformation by the metal properties. However, on close examination of the receiver it is relative thin directly behind the standing breech and on the sides near the standing breech. I have already changed the design to leave much more metal ~1/4 inch directly behind the standing breech and will thicken the side panel (boss)as well. This will add much more cross section to the weakest area. I will leave the shape the same but simply make them thicker. I need to add something here for 21 owners who might have a shotgun made after 1960. At the beginning of the custom shop era Winchester decided that the boss was not needed for strength or integrity of the receiver and that has certainly been proven true for the shotgun. However, I do not believe that to be true for a DR conversion. So, I would highly recommend that you not add a DR set of barrels to a straight sided Winchester 21-----------my opinion.

This is one good example of an advantage for the CAD/CAM approach. The modifications are not that hard to make. It will take considerable experimentation to demonstrate to me that all is safe and that is the most important thing.

Thank you again for the reference to David. It has been very important to me. I welcome any and all comments and advice.

I have made some progress and will post some pictures in a few days.------------Bill