Is reloading data the same for the standard powder and the "SC" powder? Specifically, H4831SC in .257 Roberts...

Yes

PEDESTAL,
Since Hodgdon started having their extruded powders made Downunder, the size of the individual grains of powder have been reduced in size. The only exception to this is H-4831. As I understand it due to such a strong following of the old style powder it was decided to offer H-4831 in two sizes of grains. The old style large grain and in the new smaller grains. As a means of identification the labeled the new sized powder as H-4831SC, and the old sized powder simply as H-4831. Other than the grain size the two powders are identical. The new sized powder takes up much less space in the case than the old sized powder. The large grains helps keep the load density in the older H&H cases. The new sized grains allows more powder to be used in some of the smaller cases in which the 4831 burnrate is wanted but not enough of the oldsized powder would fit in the case. I got my information in an article so I may well be wrong and load density is the real reason for the two different sizes of powder grains. Have fun all.

The powder you use called H4831 maybe a grain or faster than H4831SC, but I am guessinga bit.

In Australia it is called 2213SC. Before that we had 2213, which was supposed to duplicate the "old" 4831 and it do that. Both qare the same grain size. As far as I am aware, America never got the older 2213. The older 2213 has been discontinued down here so that there is only the one powder for both America and Australia.

The 2213SC is supposed to be about a grain or so slower than the older 2213 and since 2213 duplicated the old 4831 then SC should be slightly slower.

The powder you call H4350, if that is the short grainpowder then that is 2209 down here and is around IMR 4831 burn rate.

Mike

this is an edited extract from the ADI handloaders guide, hope it helps you.
"ADI produces AR2213SC for the North American market. AR2213SCis repackaged and distributed by Hodgdon Powder Co.in the US under the brand name of "Hodgdon H4831SC".ADI also produce AR2213H for Hodgdon, being "HodgdonH4831" in North America and Europe. AR2213SC and AR2213H have the same burning rate and bulk density (charge weights), but AR2213SC has improved metering characteristics through a shorter cut length of grain".