Uploaded yesterday on YouTube by Hephaestus is an actual field test of the GHK Airsoft M4 Gas Blowback Prototype Rifle. This is an anticipated rifle given the expectations of getting a heavier kick in recoil which GHK are known to be with their products. Test shooting and using it in actual skirmish is shown in the video which you can evaluate if it gives a more realistic M4 recoil

More photos of prototype at the Hephaestus Facebook Page.