5whiskey, how did you determine that most factory ammo is NOT loaded too far under max? Chronograph it?
If you did and your test barrel was not identical in all bore and chamber dimensions, mounted the same way, used the same lot of primers and powder, cases had the same neck tension and the firing pin had the same impact parameters, then your data will be different than the factory data.
I ask 'cause chronographing ammo's how most folks make comparisons.
What ammo makers use 26" test barrels?
US Navy Distinguished Marksman Badge 153
Former USA Palma Team Member
NRA High Power Long Range High Master
NRA Smallbore Prone Master