What does the caliber designation, "30-30" mean?

What does the caliber designation, "30-30" mean?


The 30-30, or 30 WCF was the first American small-bore, smokeless powder sporting cartridge. It was designed by Winchester and first marketed in early 1895 as one of the calibers available for the Model 1894. The original loading used a 160-grain softpoint bullet and 30 grains of smokeless powder. Thus the name 30-30 for 30-caliber bullet and 30 grains of powder.