LRF,
Only because you put a lot of weight on using a 30 caliber barrel you have on hand and wanted a cartridge large enough to kill deer and not too large for gopher. The 30 Herret has killed a lot of deer, but whether it is too big for gopher is really a subjective question.
If I were building it for myself, I would make it 5.6x50R(deer legal in my state and loaded with 60 grain Nosler kills them "graveyard dead"), but I'm not building it. Since you are building it, you get to do what you want, for your own reasons. There is no doubt that when you finish with whatever caliber you choose, the result will be great.
Mike
