The mossberg 500 series with the extended magazine (8 shot versus 6 shot) will not take the standard Mossberg barrels, with a changeble choke, or a fixed chokes mod. or full, which negates your ability to easily change barrels for hunting and self deffense.
You can shoot skeet with a 20in. barrel but it will not be easy. If I were you I would look at the mossberg combo gun it comes with a standard 500 with 6 shot magazine, and either a 26" or 28" barrel for hunting, and a 18" barrel and pistol grip for deffense. I own one pf these kits and it worked out great but I don't use the pistol grip. To change from hunter to deffender take off long barrel turn gun upside down shake out the plug and install short barrel.
