As far as I know, the only difference is the gas ports. Two 0.060" ports on a 2-3/4", and one 0.067" port on the 3". MAYBE the action sleeve is different. I know positively those are the only differences on the 12 and 20 gauges between 2-3/4" and 3" guns, but I cannot find my old parts list to confirm if there were two different action sleeves on the 410s. They quit making the Magnum action sleeves for 12s and 20s when the 11-87 came out. Current parts list shows only one sleeve for 28 and 410, and no mention of "Magnum". All parts, including the receivers, are identical on the Model 1100 12 and 20 gauge 2-3/4" and 3" guns except the barrel ports and the action sleeve, and I would think the 410s were the same, but it has been a long time since I have fooled with one. Never was much into 410s. I have measured and weighed a bunch of 12s and 20s over the years to be positive.