I recently loaded both some 44 Specials and 357s with some 2400 that was marked 1978. Worked great (as it always did) in both loads.

My 357s were a bit warmer than yours and I DID shoot some in a 19-3, too. I always use mag primers (or WW primers that don't distinguish mag from regular) with 2400 -- just cuz they say to do so.