Multi-stage tumbling, with progressively finer grit, will get you to an arbitrarily fine finish (it's just a matter of time and number of grits used).

A caveat: it might not be possible to eliminate the coarse surface texture of the forging, but the surface of the bumps can be made very smooth. Think of the surface of the handle of a (new, clean) crescent wrench.

see also

http://www.practicalmachinist.com/vb/cnc-machining... - especially the last post

We do a number of such forgings, and we're getting very good finishes right off the dies, but nowhere near reflective. Talk to a mass finishing vendor about possibly doing a steel media burnish or even perhaps electropolishing. It's worth an inquiry.

It is better to have enough ideas for some of them to be wrong, than to be always right by having no ideas at all.

I recently had some 1" diameter aluminum (I think 6061-T6) machined balls tumbled to something approximating a nominally mirror finish - sorry I don't know details of what media etc. they used.

So ditto what btrue says, depending just how rough the forging is initially.

Search around at PFonline.com, I know I just saw something about different media types and how they affect optical characteristics. Here is one link about getting mirror finish on SS sheet, not what I'm looking for but interesting none the less.

http://www.pfonline.com/articles/in-mechanical-fin...

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The Help for this program was created in Windows Help format, which depends on a feature that isn't included in this version of Windows.

One type of media finishing that can produce high reflectivity is Isotropic Surface Finishing (ISF).