I hope this isn't a repeat or duplicate! If it is then just ignore this post.
I found it while doing a web search and thought some here might enjoy it as well.
www.answers.com/topic/list-of-firearms#wp-MList of firearms
This is a long flat list, mainly of firearms, including the usual machine guns, rifles and shotguns, but also some other man-firable weapons such as grenade launchers. These range from pocket pistols to anti-tank rifles, including the weapons of soldiers, police, and civilians. The list is not complete. Many models are listed multiple times, and there are numerous misnamed variants. Major variants are listed for many but not at all for others. Many variants link to a single page. Multiple names are okay to leave, so that redirects can be made for them.Here's the link for the M-16 (lots of interesting information):
www.answers.com/main/ntquery?method=4&dsid=2222&dekey=M16+%28rifle%29&gwp=8&curtab=2222_1