If you order a 434 bullet from LBT it will size to that diameter, as I guarantee at least a few tenthousandths over what you ask for and not more than .0015 (1 1/2 thousandths of an inch) over what you order.
A 300 or 320 gr LFN will outshoot accuracy wise, any bullet you can put into a revolver. But S&W's aren't tough enough to run those weights full throttle on a stead basis.
Get the 300 gr and load light, to about 1200 fps, for long gun life. It won't hurt the gun to load them to max for hunting if you don't shoot them by the thousands. The problem with S&W's is not strength but that they shake apart quicker than single action revolvers when recoil is severe.
