Ditto on what Kevin stated. DO NOT shoot a fire arm through the mesh. A fire could ensue.

As for worrying about the muzzle sticking out of the blind....I would not worry. Last fall a buddy of mine was hunting out of the blind with me. He had his flintlock and I was using my bow. A doe walked out into the field about 90 yards away and he proceeded to take 3 shots (and 3 misses) at the deer with that flintlock before it decided to high-tail it out of the field.

You should not have a problem using the muzzleloader in the blind...