I have had good luck with the old 405 Grain Remington Coreloks in my Ruger #1. As for loads a good charge of IMR 3031 and a 350 grain Speer or Hornady is an old standby. My own load uses 58 grains of Vihta Vuori N-133 with a 350 grain Speer or Hornady. I use a Lee factory crimp die to put a good crimp on it.

I cradle the forend of the Number 1 when I shoot it off the bench. The old Remington load may be old fashioned, but a friend of mine hit a mature bull bison in the forehead with one and found that it had finished up in the third vertebra. He was impressed.