We are sorry that your GK1 requires service. In the US, warranty service is handled by Huben's authorized service centers. We have arranged for that work to be handled through our distributor.
Please send your GK1 in it's original packaging to:
Huben Warr.
11976 Judas Ear Ct
Att Phil S.
Please make sure to include your full name, shipping address, phone number and email so the tech can contact you with any questions and, most importantly, return your airgun to you after the service is complete. Warranty service usually takes about a week after it's received.
Include a copy of your order documentation as proof of purchase to avoid any delays in the verification process of your warranty. Make sure your airgun is well packed so that it is not damaged in transit. Pressurized air cylinders cannot be shipped by air.