I inherited an unused 870 Express. On the gun, it simply says "Remington 870 Express" and on the box it says it's the Remington 870 Express Combo. It came with 2 barrels and both says something to the effect of "Can use 3" and 2 3/4" loads in magnum models. All other models use 2 3/4"". I'm guessing it's not a magnum since it doesn't say magnum anywhere. Is the gun actually chambered at 2 3/4 or is it just the barrels? The new 870 Express looks to be chambered at 3" according to Remington's website. I just want to know if this gun can handle 3" loads if I get different barrels for it or if the gun itself is actually chambered at 2 3/4. Is there anything on the web I can use to look up serial numbers that will identify the gun? Any help appreciated.