Yeah, there's clearly some shading and smoothing problems going on in your Poser renders, but not as bad as I would have guessed.  Frankly, there's a lot of marketplace objects out there that have worse surface shading.  Looks like most of the strange shading issues are coming in areas of the model where you don't have edges defined, and leaving the renderer to guess at how to divide the faces.  Do you have a shader applied to the model?  Are you rendering with AO?

Poser is one of those applications which prefers uniform quads, and it does strange things with tris and especially ngons, as you can see.  Glad to see you cleaned up the back face of the stock, because it's rendering much better than it would have if it were left as an ngon.  Good work there.

One of the biggest problems I see is in the clip and clip holder of the gun.  The shading there is very bad, and I can see why by the wireframe.  You have some awkward ngons in those areas, which are being divided by the render engine poorly.  I would say you might need to fix that area by getting rid of the ngons, because it's just not going to render well in Poser.

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Tools :  3dsmax 2015, Daz Studio 4.6, PoserPro 2012, Blender v2.74

System: Pentium QuadCore i7, under Win 8, GeForce GTX 780 / 2GB GPU.