Check out these awesome GUn cut aways from Ukrainian artist Abiator. Below he has cut aways of the Colt .45 the AK47 and even a MGL m32 Grenade Launcher. Also, Abiator has some pretty cool renderings of conceptual weapons from Sci-fi and a pretty realistic Delorean rendering.
AK-47, The model has 60k triangles Whoa! Thats a Hell of alot of Triangles! But totally worth it because the rendering is spot on and looks totally realistic.
The MGL m32 Grenade Launcher Is more than just a cut away its a dissection of the weapon and a part by part description.
This Delorean is a Low-Poly render but the advanced texturing and lighting gives it a Fantastic Real look.