Nice scene. Some details could be improved though, imho : The primer's edge is too sharp, and the material of the primer should be slightly different (different brass, stainless or red copper). The embossed caliber and logo on the shells, around the primers of the cartridges looks like printed instead of embossed. It is due to the fact that you didn't blurred the texture. Increase the size of the font and blur it a bit, and you will get a better effect. The material of the shells (brass) is poor. Always think that metallic materials like chrome or brass require something to reflect. You seem to have used an HDR or LDR environment, but often it is not enough to get good reflections, and a plane with a texture with some emissive value could be used to lit the scene over the shells, or simply dicreasing the roughness could be sufficient.
I made the scene below with Blender internal render engine 3 years ago, so I am sure that better effects could be achieved with Octane.
http://3d-synthesis.com/33-Colt1911A1.html
Anyway , nice composition, and funny joke on the bank notes !

French Blender user - CPU : intel Quad QX9650 at 3GHz - 8GB of RAM - Windows 7 Pro 64 bits. Display GPU : GeForce GTX 480 (2 Samsung 2443BW-1920x1600 monitors). External GPUs : two EVGA GTX 580 3GB in a Cubix GPU-Xpander Pro 2. NVidia Driver : 368.22.