I am fairly new to blender and 3D modeling in general, but would like it if anybody could give me some feedback on how to make these bullets look better. For reference they are supposed to be S&W .40 bullets.
A couple of things. Reflective objects look better when they have an environment to reflect. Right now your shells are just reflecting the default gray environment color.
http://www.swineworld.org/2012/12/how-to-set-up-simple-hdri-environment.html
Also, it looks like you have some artifacts from applying the Smooth shader to edges that are too sharp. You need to add some additional edge loops (Ctrl+R) to the model [one loop on either side of the edge should do it.]
Steve S
Bullet is the heavy part at the top and when it’s in its case, it’s a cartridge or a round. Not sure if the intention is to get critique on the bullets only.
Either way, the first step always is to get some references to see how they commonly look and how the material behaves. For just material, it doesn’t have to be the same exact caliber, so google image search “40|44|45 full metal jacket cartridge|round” gives nice results. Limiting results to big images, even nicer.
Those are metal which means reflections, so a good environment they can reflect is crucial. A good quality high dynamic range image should work nicely. The materials get different amounts of scratches, dents, color variation, depending on how new they should look.