http://screencrush.com/seinfeld-the-bet/

The 9th episode of the series would’ve tackled the controversial subject of guns.
Read more at http://www.hitfix.com/tv-tattle#TD6uRsWG6QCgB62v.99

never knew about this...

So in a way this would have been Seinfeld's first and only take on the "special episode".