The A&K, CYMA, and Classic Army SR25/M110’s come with a full cylinder if the replica is equipped with a 20” outer barrel and ~500mm inner barrel.
The A&K is lower priced model but it doesn’t have a QuickChange Spring Guide system in it, and the internals aren't all that hot. The CYMA’s mosfets seem to have a problem with 11.1v’s and can go bad, seems people are using PerunHybrids if they fry, but the rest of the internals are pretty good. The Classic Army SASS has, hands down, the best mosfet/trigger unit, it has a bore up setup (in addition to being a V2.5), the motor is a bit weak, and a 24mm nozzle is needed to replace the 23mm if using any other hopup bucking than the factory one (ask me how I know).
I usually recommend the CYMA because its more available than the Classic Army (pretty sure the SASS models are unicorns these days). If CYMA would up the game on the mosfet and microswitch, it would be a total knockout.