Max velocity is whatever your rifle and your nerves can stand and is NOT a good criteria to go by.

I've been working on loads for my 375H&H and 9.3x62 the past week and here are my data.

9.3x62 rifle is a converted military 9mm VZ-24 Mauser with 23.7" Lothar Walther prefit barrel and a 0.190" longer throat at 3.26" COAL. COAL is limited to the mag length but I use 3.26" - 3.28" mostly.

286 gr Horn...RL-15 and Varget...top or slightly over top loads 2530fs plus/minus...Varget is ~100fs faster with same powdere amount...R-P brass Fed215 primers...Beta Chrony. Accuracy is the same for both powders...3/4" or slightly less for 3 rounds at 100 yds.

270 Speer...RL-15 and Varget...mostly over top loads...~2640fs +/-...same as above for the rest of the data.

This is fairly close the the 375 data(21" bbl) so I think the Beta is not reading fast...and I doubt any animal could tell the difference in the -.009" bullet diameter, 15 gr difference in bullet weight or the 150fs in velocity...but my pocket book can tell the difference in the 25% more powder in the 375!!!!

This rifle showed a marked preference for the top loads...a difference in 2 gr less powder for BOTH the powders would open the group to a vertical 2 - 2.5" string and didn't go into a nice triangle until above the listed maxinums. My long throated 338-06 showed the same inclination. THIS IS NOT A RECOMMENDATION TO GO OVER SAAMI SPECS...you have to work the loads up starting midrange...SLOWLY...

None of these loads showed any pressure signs other than slightly flattened primers...bolt opening was the same as on an unfired case, extraction was without ANY hitches and cases could be reloaded a minimum of 10 times without showing ANY signs of impending head separation.

I think the Beta Chrony is fairly close as the data for this rifle AND my 375H&H is very close to what the several manuals and magazine articles list.

I ordered a muzzle break to install not for the recoil reduction but to keep the muzzle down...this particular rifle likes to jump around...1.5 to 2 ft of muzzle rise on the bench and a good foot offhand. I have MB's on my other big boomers for the same reason. The 375 hardly moves any direction except backwards off the bench with 300 gr bullets and is much more pleasant to shoot than the 9.3. Go figure.

Luck