A chronograph is your friend.

FWIW:
I have a couple of different molds that cast the 240gr/245gr keith swc's for the 44cal's.
A early ideal mold with square lube groove casts bullet that measures from the base of the bullet to the top of the crimp groove .450"
A 2nd newer mold casts a bullet from the base of the bullet top the top of the crimp groove .475".

The lyman 49th addition lists:
429421 1.710" oal use of a mag primer 4" bbl
h-110 24.0gr 1218fps to 25.0gr 1301fps

With all the different designs/styles of the "keith" swc for the 44cals. The oal really means nothing, it's the amount of case capacity that the bullet takes up/uses that's important.






The pictures posted above are of cases with a lot less case capacity then the 44mag. I simply posted them to show how the amount of the bullet in the case/case capacity can affect the pressure of the load.

I swage a lot of my own bullet or cast bullets from obscure molds that their is no data for. I always measure the amount of the bullet that is going to be seated in the case and compare that to known bullets/data.

I have a 29-3 that has .4330 cylinders and a .4297 bore. I use a .432 bullet. I've never had the best luck/accuracy when I have either sized bullets down more than 3/1000th's or shot them and the bbl sized them down 3 or more thousands.


Let us know how your test loads work out.