Just a thought off the top of my head...30-30's are made for the shorter, lighter bullets; 150gr(I think) flat point. I don't know if a factory barrel will stabilize the 175gr Spire point. I have personally had good luck shooting long bullets in slow twist barrels, but it could be an issue for you.
On a different note...you are doing exactly what I have recomended to several people. I'm military living in Montana and have had several people from back east transfer here. "All I have is a 30-30, can I hunt with it?" ABSOLUTELY!!! If you want some more range out of it though, reload pointed bullets in it and make it a two-shooter (ONE in the tube and one in the chamber), VIOLA, a 308-light.
Genises 27-3: Now therefore take, I pray thee, thy weapons, thy quiver and thy bow, and go out to the field, and take me some venison...