I have 2 reloading benches. On the heavy one I glued and nailed 2x4's together on edge for a solid top then used an industrial sander to smooth the top.
The other I use for shotgun reloading. The top is simply a 4' counter top putchased at a Lowes or home depot. The top has a backsplash that keeps stuff from falling off the back, kind of nice. The counter tops are reasonably priced as well. Not as heavy as the 2x4's but plenty good for shotshell reloading and I would not hesitate to use it for metalic reloading either