Which would your pick in this comparison of SIG MCX Rattler Gas Blowbacks by Yi Workshop. The versions are from APFG and Falcon Toys, with the former already a familiar GBB to airsoft players. They check for the external features, internals, as well as a shooting test. Watch the video to find which did better.

Task Force 18 show how to assemble the 3D-printed MCX Rattler Upper Receiver Build designed to use on the Tokyo Marui NGRS AEG... "Assembly video of the MCX Rattler upper receiver for Tokyo Marui NGRS Next Gen Recoil Shock system. All parts were 3D printed on a Creality Ender 3 in PLA plus."