Perhaps someone ordered a 30-03 from the custom shop.
Why would they do this?
Originally, the 30-03 was designed to shoot a 220 grain bullet. When they switched to a 150 grain bullet, they shortened the neck a bit and we call that the 30-06. (All the Springfield '03 rifles were recalled and the barrels were shortened from 24 inches to 23.790 inches.)
Perhaps someone in the 1940s wanted to hunt stuff with 220 grain bullets and specified the 30-03 for that reason, though 220 grain bullets work fine in the 30-06.
