Originally Posted By: Michael Petrov
My best guess until I get more or better information.

Griffin & Howe next assigned blocks of numbers to particular calibers starting sometime in late 1923.

Barrel Number Caliber Highest No. Recorded
101-150 .30-06 147
151-200 .35 Whelen 166
201-250 .400 Whelen 228
251-300 7X57 300
301-350 .250-3000 314
351-400 25 Whelen* 351
401-500 .30-06 494

* The .25 Whelen was a version of the modern .25-06 or .25 Niedner.


No. 500 was a .300 Savage originally....or there are more than one....