I am fairly new to shotguns and i decided to get an 18 in barrel for my remington 870 supermagnum. I bought an 18 inch barrel with a fixed choke that will handle 2.75 and 3inch shells with the supermagnum receiver but my receiver is chambered for 3 1/2 inch shells. Will my gun be safe to shoot as long as I dont use 3/12 inch shells through the barrel i just got?