I would recommend going to the improved cylinder. The modified might do too much distortion of the slug. As long as he is shooting rifled slugs(Foster), it will be fine. People have been shooting these for years with great results. And tell him to let the barrel cool down a bit when shooting. It is just getting over heated. When I used to shoot trap leagues, by the end of the round, my gun was so hot you could only touch wood, and you could see the heat waves coming off of the gun. I shot 4 rounds of trap, three nights a week, with no adverse affects to my gun.