Attached Link: panko' store

two things to bear in mind. One is if you are planning to make commerical renders a  lot of vendors have a 'not for commercial render" rider in their EULA, or sometimes they merely say you can use it for commercial if you credit them, so if it is a commercial project then free stuff is not your best option. Secondly I once spent literally a couple of weeks (admittedly I was pretty new to poser) trying to make the girl hold the gun in both hands and still look good.

My favourite stuff is by panko here in the MP who has many guns and poses to match.  The guns shoot bullets and discharge the empty shells, you can cock them and put up the sights etc, and one of his machineguns even has a bullet chain as well.  For what you get it is well worth it, and there is even his vietnam set that has some gear/clothing as well.
His stuff is also available at vanishing point and I know they were having a sale recently.

His stuff works like this usually.  you zero the poser person and load the gun and zero it too.  then apply a setup pose to the gun and to the person (all provided with the gun), then you parent the gun to the hand via parent figure menu item, then apply the shooting pose or standing holding the gun pose etc to the poser person, and one perfectly positioned poser person holding the weapon.  Once the gun is parented to the hand, other people's poses applied to the poser person also work quite nicely with it too on the whole. 
Love esther

MY ONLINE COMIC IS NOW LIVE

I aim to update it about once a month.  Oh, and it's free!