No problems yet
I also do duracoat, Gunkote,Gearkot and ceracoat and a little over spray in the receiver will not cause any operating issue. I've gone as far as using KG gear coat on some bolt carriers to see what would happen. Yes it will ware and show some marks, even chrome or nickle will show some marks. Zero Fail has reports of it flaking off. But I've never had an AR fail or have issues from the gearkote. Now if you do something wild and give it a five mil coating in certain areas it may cause a problem. Now the gearkote is designed for piston skirts, which is similar to the BCG moving rapidly in the receiver of an AR 15. But remember that KG is made for tight tolerances, high pressure and high heat. I like KG because it does dissipate heat very well and is, or, was used on water pumps, radiators and oil cooler for high performance cars some time ago. For a poor mans coating it worked well. It's what we got until they come out with a home kit for Tenifer and NP3. FYI KG has a ceramic coat for piston domes for continuous 1200 degree use. Remember there is now Duracoat SL and quicken to add and KG has a good pre phospate before spraying. The impact area on hammers is a waste of time but areas the move close or rub a little will be fine. My mag wells are slick as snail snot with Gunkote. It's trial and error on some but you'll figure it out like the rest of us rocket scientist. Good luck and have fun doing it.