Have a situation, 375 Flanged NE 2 1/2 and 405 Win barrels for the same action, a Charles Lancaster falling block.

Back story: Charles Lancaster falling block was rebarreled (supposedly) by Holland & Holand to 375 FLNE 2 1/2 in 1923 and barrel is marked Cordite 40 - 300 MAX, then rebarreled again in 1960s to 405 Winchester with the firing pin bushed. I have both barrels, both have solid uninterupted thread. Gun has been fired with 405 WIN factory ammo (SAAMI) and 375 FLNE 2 1/2 published handloads.

CIP pressure for 375 FLNE 2 1/2 is listed as 2,200 BAR, 31.9K PSI and CIP pressure for the 405 Win is listed as 2,500 BAR, 35.5K PSI. 405 Win factory loads and the 375 FLNE 2 1/2 hand loads are higher than the CIP 375 FL NE 2 1/2 per CIP specs and my friends Qload data.

Action has been disassembled and inspected for damage and non was found. Locks up tighter than a fault.

My question is should I load the 405 Win to the 375 FLNE 2 1/2 CIP pressure or continue to use 405 factory loads ??? I think the 405 Win shoulkd be loaded to 375 FLNE 2 1/2 CIP pressures.