Don't use certain ammo - International Firearm Corporation Ifc Upper Receiver .410 2.5" 18.5" 9rd Flip-up Sights/rail

so the chamber length is 3 inches, but you have to single load them in as the magazine can only hold 2.5 inch rounds. the thing is not all 410 2.5 inch rounds are perfect. word of the wise, don't put in Winchester super x ammo into the magazine they're too long by only about .200 of an inch. Remington game loads should fit just fine as they are a little shorter than 2.5 by about .240 of an inch so unless you're getting failure to extracts or failure to fires. it isn't the upper.its the magazine. simply make sure you've got the right ammo before slapping a 1 star on something that does deserve more. so if you just pull some 410 shells out of your judge make sure they're not 3 inch shells or longer than 2.5 inches. cuz that extra .200 of an inch makes a difference in feeding from the mag.
good product. never fails as long as you feed it the right food.