Nope,... Erm, the muzzle_tag is a particular vertex, which is managed differently on every model editor, therefore you'll just import any AC weapon model 'into' your model file. Now you'll have your and the official model in one place. The original model has the muzzle tag! So you can use it for your model, but of course the 'rest' of the imported model isn't needed, so you can just remove it again and keep the one vertex which effectively is the tag you're asking for.
Got it? I can't explain it any better, sorry. :)
Got it? I can't explain it any better, sorry. :)