You a very punny guyyyyyy
I don't have either of those bullets in my drawers (he-he), but you might try measuring the bearing surface. I'll bet the 39 grain Blitzking has a longer bearing surface and hence, more drag going down the barrel.
Could also have to do with jacket composition too, as you mentioned, or both. That's why the recommendation to back down on your charge when switching bullet mfgs. and work back up checking for pressure.
Are both bullets seated to the same depth into the case and have the same neck tension? That could also be a factor.
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