I thought I would post an interesting finding that I discovered when installing NDS-38 peeps on our .44 Mag barrels (forgive me if I am being redundant here). In measuring the barrel diameter at the breach end, between the two rear scope holes... I found it measured 1.111" so the surface to bore center is 0.5555"... out of curiosity, I pulled out a few different Handi caliber barrels and measured them in the same location... all were 1.111" in diameter. I measured .22 Hornet, .223, .243, 7mm-08, .30/30, 7.62X39, and .44 Mag barrels... all were the same 1.111" diameter (someone might want to check .45/70, but I would expect it to be the same as the .44 Mag)... So someone would be pretty safe in using 0.5555" as the measurement (plus actual peep height) to determine front blade/bead height.
Inceidentally, with the NDS-38 peeps (which are 0.530" high to peep center + 0.5555" = 1.0855" total height), the barrel diameter at the front blade location is 0.846" requiring a front blade height of 0.6625".... I used the Williams Firesight bladed ramp which is 0.634" high, but sits higher due to the base curvature being for a .650" barrel... it worked out to 0.655" height... close enough.