Always wondered how the large ammo manufacturers verify the velocity of their loadings considering that they do not use commercially mixed powders. Do they measure velocity for each powder lot mixed for the given round or do they have some other ways of measuring it?

Ammunition makers do not blend lots, they accept a lot of powder from the manufacturer and load it as-is.

There are two considerations, can target velocity range be reached with that lot of powder at acceptable pressure limits for the cartridge. If performance within desired parameters can be obtained they load that lot of powder with the calculated powder charge until it is gone. Several cartridge types may be loaded from a single lot of powder.

__________________
Gunsmithing since 1961

When Speer first started, they built their own testing tunnel.

No equipment?
Send it out to a lab.............. no big thing.

I would love to spend a day at an ammo plant speaking with their personnel. Would be great to see if they kept records of their specs and tests from yesteryear - guess what I would inquire about? Yes, you guessed it, 38 Special loads!