Brass,
46.5-47.0 grains of 4895 under a 168 used to be "the" standard load for 30-06 Match ammo when th M1 was still seen in the HighPower competition circles. Standard powder for military ammo for many, many years, and won't be a problem for the op rod. Burn rate, not pressure, is the real problem here. You can use relatively mild loads of slower burning powder (say, 4350) and it WILL damage the op rod, due to excessive port pressures, Stick to 4895, 4064 or others in that same burning range or faster, and you'll be good to go. I'd also suggest avoiding bullets over 175 grains for the same reasons. Great rifles with a fine history, but they do have some very specific feeding requirements that need to be followed to keep them happy.