Motokamishishii's guns are fully articulated replica's, from what I gather one of the best you can find for realism and detail for Poser, looks like mostly pistol replica's though.

http://www.renderosity.com/mod/bcs/index.php?vendor=342356

For larger caliber weaponry and auto rifles, FoRender is the bomb... The gun models are just magnificent ( I have one of FoRenders Ak-74's and for a gun it's a thing of beauty). Highly recommended. $7-12 for quality models is a bargain, How many different types of guns do you need?

http://forender.com/