Get repo file here:
http://www.roblox.com/games/239581804/BUG-Testing
Having a weapon with welded attachments creates this bug. When you set the CFrame of the handle it will not change the handle cframe correctly. Instead your handle cframe will be rotated completely out of bounds. Just because some attachments have welded parts to themselves. Welding parts to other parts should not be an issue.
Please take the file and see for yourself. If you remove the Part in Holo model, then the cframe is set correctly.