Hey guys, I have a Gen 3 21SF that I have set up with an ISMI 22lb. recoil spring and ss non-captured guide rod, and LW 6" non-ported barrel to be able to shoot .45 Super rounds. I just got a new Gen 4 20. I really like everything about the gun and was wanting to get a Gen 4 21 and set it up like my Gen 3 21SF to be able to handle .45 Super ammo. I know I would have to get a Gen 4 adapter to fit into the front of the slide to be able to put Gen 3 type guide rods and recoil springs in the Gen 4 slide. Has anyone tried the Gen 3 type guide rod and recoil springs in their Gen 21 yet and how does it work for you? Thanks! Wanna kill these ads? We can help!