The link you posted was for a 12 gauge Model 1100 Magnum with a plain barrel. Please don't get offended, but I think you need to do some reading and undestanding before you jump the shark over a gun.
A 3" Magnum 1100 will work with with 2-3/4" Magnum shells also, in either gauge, but how well it works with other lighter 2-3/4" ammo is going to be an unknown until you try the particular gun. Also, many 1100s have been "Bubbaed" by previous owners. I have seen a cracked receiver on more than one. I am an 1100 lover. When one guy cried to me about his cracked receiver I looked at it and the gas ports had been drilled out to 1/8". I asked him and he assured me he had checked another one and it had 1/8" ports. The one he checked was an 11-87. Totally different, and I was not surprised at the results. He is now convinced 1100s are junk. He is a computer whiz, but he couldn't understand gas dynamics in forever.