Unfortunately we can’t really help with this issue since FE gun kit uses its own code, module, API, etc meaning the only way someone would be able to help you would be if they understood the code and knew how to do as such. The only way you can fix your problem is by either doing the latter or making your own gun kit.
It’s going to be difficult to help due to the fact that since the FE Gun Kit by thienbao2109 uses it’s own API, code, modules, etc. I would highly recommend to just learn how to make your own guns as it will help you familiarize with using raycasts, maybe fastcasts if you want to use that instead, etc. as it will help you improve at programming. I personally just don’t even know FE gun kit that well, and the most I know is the original one by SuperEvilAzmil, which is the version that was first made in 2016 that used original raycasts.