OK, so the guy used McIntosh as an Ithaca reference. Snipe Hunter, around these parts using any Ithaca reference not quoting Walt Snyder is akin to defiling virgins, raping dogs and shooting over and unders. In this case you're safe since McIntosh's data is quoted from Snyder. Your information is correct- before August, 1924, 2 5/8". After August, 1924, 2 3/4". Enjoy a fine field gun and remember what GrandPa used to say, "Son, quit worrying about the mule going blind and just keep loading the wagon."