I recently acquired a Winchester model 100 in 243 Win. What powders would give the proper burn rate to cycle the action. I would be loading 100 gr. Sierra Pro Hunters.

I've three .243's over the years and and had very good luck/results using IMR 4895. It's one of the powders that they recomend for the M1 Garand and M14/M1A1 so as to not damage the gas system in these rifles. IMR 4064 is amother good choice as is IMR 3031, these also are recomended for this type gas system plus you can use standard primers if you wish also.