Lol, CCI makes the Phantom, A Nelson based pump. CCI has been around for like 20 years, and they make a quality product. Nelson or Sheridan based means which internals are used.
Nelson based means it uses Nelson style internals originally designed by the Nelson paint company for the Nelspot and the Nelspot 007. Many guns like Razorbacks, Tigersharks, and lots of other guns use Nelson internals. All Phantoms use them except maybe the revolution.
Sheridans on the other hands use Sheridan style internals originally from the Benjamin Sheridan company. Guns like PGP's, PMI-1's and KP2 and KP3's use them, along with all autocockers and Snipers. Snipers are pump Autococker.
Phantoms are usually set up as a stock class gun, because they are light and 12gram efficiency.
Sheridans are usually set up as open class, Just look at any CCM gun or almost any Autococker.
Personally I don't really like Nelsons, they are very light. I like a little weight in my hands so I prefer sheridans which are usually a noticeable bit heavier. I also prefer Open class, While stock class is fun if everyone is doing it - I can't do it with a bunch of semi's, I like having some extra paint and air.