I have bought some of his designs. They are configured to use the airsoft mechanism and no barrel recoil as the barrels are fixed in place to mate up to the airsoft gun. I will be printing some of them, but modding them to have barrel recoil and no airsoft. The I was going to start with the Oplot, but I may print the E100 first. The designs aren't totally accurate which is why the E100 is a great choice. You can use some creative license with it since it was never produced.