I've seen the guns. Who makes 3-inch 28-gauge shells?

In the U.S. we had 2 1/2 inch --



and 2 7/8 inch 28-gauge shells --



up to WW-II --





The progressive burning powder, high velocity, 28-gauge load with 3/4 ounce of shot was introduced circa 1931-2 --



then just before the War skeet loads began being offered in 2 3/4 inch shells and quickly after the War the 28-gauge was standardized at 2 3/4 inch.