GP:
Actually, you are not far off from a great round IMHO. I have always thought the 300 Savage was a better starting round than the 308 for an easy IN legal rifle. I was not able to find the info I wanted on the 35 IHSMA (essentially a 35 - 300 Savage)so went the route of 35 Remington.
Rebarrel with a Rem factory contour that measures around 0.66 at the length you want. Then find a reamer or have one made. Have some dies made and your good to go.
Scott
