weapon_arms (from your config) dont exits, you need a arms plugin like this
https://forums.alliedmods.net/showthread.php?t=290276
About m4a1 check that its downladed from server correctly (you have the files on your local csgo directory), check that the route is allowed on the pure server settings if you have it enabled, and see if another models works well and if that is the case then maybe the problem is the model itself.