Use of long barrel on 930 SPX
I ordered a long barrel (28"?) from Mossberg so that I can use my tactical 930 SPX for sporting clays. The Mossberg rep that took my order didn't recommend any additional parts, other than the barrel and a choke, so I want to make sure that I am not missing anything, i.e. the new barrel will be a direct replacement of the existing short barrel? The manual takedown instructions, which were not specific to the SPX model, refers to a seal ring adjacent to the gas mechanism, which is stated as "may have". My SPX didn't have this ring, but I am wondering if I need one with the long barrel? Any help or insight is greatlly appreciated!