Ron; Glad you found a long chamber in you 9.3x62. I am building one now using a VZ24 action, mag length 3.31 max COAL. Ater headspacing I found the COAL for a Speer 270 to be 3.48" touching the lands and COAL for a Hornady 286 to be 3.52" touching, definitely too long for the mag and well over the 3.28-3.29" standard seating OAL. The crimping groove on the Hornady 286 limits the COAL to 3.18" for an even worse jump if it is used.
I checked with the barrel maker to find out the story and they said their chambers were to CIP and SAMMI specs, and the jump doesn't seem to bother accuracy. Time will tell.
The large amount of jump...or "freebore", if you will, "might" necessitate a bit more powder to equal factory or published velocity specs, but you will need a chrono to check this out for sure in your rifle...if all chambers are cut with this amount of jump standard then published information should be taken as printed and no adjustment is needed.
Besides a 9.3x62 isn't considered a hi-velo rifle and a few feet per second isn't worth the extra pressure as over the normal shooting ranges even a 100 f/s doesn't do much for drop figures and adds only small amounts of energy, increases recoil and so on.
I would be interested in the amount of "freebore" you have with the Norma 232 gr and Barnes TSX bullets if you find time to publish the data.
'Njoy
