You want to be careful with that Keith Data. Old Elmer knew that of which he spoke but times change. I had a friend, gunsmith, give me some old .44 Special cases he said he bought to load for his .44 Blackhawk, yes, one of the first before the Super Blackhawk came out, bought in the 1950s or early 1960s... POINT: The cases, .44 Special, from the 1950s were balloon head.
Mr. Harvey listed loads for his .44 Special loads [he developed the zinc ring base bullets] from that era specifying that if the case were balloon head it needed 2 more grains of powder. That was over a 10% increase.
From there, you are on the road to learning. Each case, primer, etc. will show slightly different results. And commercial powder is held to a fairly close burn rate to avoid unexpected results. I had Bruce Hodgdon tell me that he stopped selling the powders that were "close" because of the liability... I had some slow H335 that said "use 3031 data." Luck.