Attached Link: http://home.pressroom.com/philips/pulser/grenades.htm

In the movie the shotgun was said to be the gernade launcher. the gernades were shotgun shell size but only silver with red caps. they were on the table when Ripley is being shown how to operate the weapon. they discharge out the 'gernade' side just like a shotgun shell would be spit out after firing. this is shown in the ripley blows up the queen eggs section, there is actually a scene if you slow-mo it where you see the shotgun shell fly out. Sorry, I'm a huge Aliens fan, and farscape too.