I'd say either a G18C or a M93R if you want a GBB pistol. In terms of G18C's TM > KSC for design of fire select. Both fairly easy to source holsters for, then it comes down to more of a preference as to which you prefer to handle. M93R is available as a KSC System 7, which helps with the cool down. Wingun revolvers shoot about 400ish FPS, which is usually over CQB field limits for MED. In terms of silent guns, can't go much more silent than a TM MK23, but the hard trigger pull due to it being a NBB can be a tradeoff.
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