I recently learned how to create my own stats for a weapon, but I’m not sure how to change the way it looks. I wanted to add more weapons to the game to add more variety, and I decided to work on an FN SCAR first. I managed to get the gun’s stats to work the way I want them too (using the Xuanlong Assault Rifle’s model), but now I’m unsure how to change the model. I downloaded a SCAR mod from the Nexus site (I don’t plan on releasing the weapons I create to the public for download, and the guy who uploaded the mod hasn’t logged into the Nexus site in ten years) so I could use its model, but when I try to change the model in the “Art and Sound” tab of the G.E.C.K, the SCAR model appears in the preview but it’s completely red. In-game, it’s still using the Xuanlong rifle’s model. Any ideas what I’m doing wrong here? Also, I've posted this question to relevant subreddits, but I got tired of waiting for responses there that will probably never come.
Photo for reference: https://imgur.com/Jk0qnvB