WW vs Norma vs Hornady cases for 220S

Been reloading the 220S and I notice when I was using WW or Norma brass with 35gr 3031 I was getting right around 3550fps which is what the Hornady factory 55gr V-Max does. I put the same load in some once fired Hornady brass and came out with 3623 average and one of them at 3732fps. Weighed the cases with spent primers and the Norma is right at 166±1.5gr, WW is 171±1gr and the Hornady is 178.5±.5gr. So it looks like the Hornady brass must have a fair amount less volume or more brass in it. Would this make for the nearly 100fps difference, just the cases? Didn't change anything else.

I'm still trying to develop a good load for the 220S but don't seem to be able to get something with a good ES and SD. Factory Hornady ammo is not bad at all. Getting a few split necks even at this lower velocity with reloads but they don't feel hot or show any other problems. Tried 4064, 3031 4895 and AA2520 so far. I've dropped the 2520 and 4064 for erratic ES and SD so far. May need to try some H380? Using 55gr SpirePoint BT Sierra. I've read good stuff about 4064 in the 220S but it's not working for me. Savage 112J.