I just bought a shooter grade 30-1 with the idea of having the cylinders reamed to shoot the 32 H&R Magnum. Will this affect accuracy with the 32 Longs?

Also, according to the SCSW # 3, the SN 753793 dates it to 1961-1970. I'm wondering if anyone can help with a closer date. It has diamond stocks which number to it and a flat cylinder release latch, together which could put it before 1966 and no later than 1968.

Thanks for your help. Bill