Many people have noticed me included something bug with this mod and maybe other weapon mods idk. Basically you launch the mod on Zombies and it works well as can be. You go into multiplayer and it crashes.
Just to inform people, this is not the developer of this mod's fault. It is treyarch.
Quoted below is the problem
JerriGaming. [author] 5 hours ago
In the latest update treyarch added something what looks like a weaponlimit. I found out that it only works when i add only 3 guns. I cant fix this issue so its all up to treyarch. Im pretty sure all MP gun mods are broken atm.

Also thanks Jerri for letting us know. Let's hope treyarch fixes this crap because mods are awesome and so are you Jerri for making a good mod before treyarch mucked it up.