Originally Posted by MSgt Dotson
With what bullet? Hodgdon's website shows 9.8 gr of 800x as max with 155 gr XTP, 8.7 gr with 180 gr, and 7.8 gr max with 200 gr FMJ....; other loading sources may give higher loading data with other bullets, but, depending on your chosen bullet, you certainly don't have unlimited headroom left...
The KKM is usually known as a quality bbl, but, I'd avoid trying to duplicate .41 mag ballistics in it, and would reserve your max loads/hunting loads to brass relegated to using only once or twice... (Case head seps are no fun at all....)
Brass will only expand to fill the chamber; attempting to gauge pressure solely by case expansion by compare DT loadings in one case with custom powder blendings with your loadings in another could quickly lead to a blowout/destroyed frame, lost fingers, etc....
The bullet used is a hornady 180gr FMJ, the load data was taken from Hornady's manual 7th edition. All loads were worked up from the starting load. There was no evidence of primer flatting. I just measure all the brass I've fired to get an idea. The brass used was also brand new brass from DT. I didnt just throw it together per say.