It was in the first Batman movie, the Joker used it to shoot down the Batwing.

Batman - imfdb :. guns in movies :. movie guns :. the internet movie firearms database
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Amazing pictures and a phenomenal website!

I can't imagine the looks I would get, or the accuracy I have have. Although.. maybe such a long barrel would actually slow down the bullet and decrease accuracy?

Either way it would be awesome to have. I haven't found anything like it yet and have been told by several barrel manufacturers that they can't do it, with no explanation of why.

Whether it's possible, or it was just a movie prop is yet to be determined but I am hoping.