So I've been doing a lot of research on this lately and thought it might be relevant here for the folks that want to polish stuff.  Since most of the polishing I do is on small parts that need to be treated lightly, I don't do anything aggressive.  Changing sear geometry or contact is bad, m'kay.  So I start with Simichrome, move up to Mother's Mag Polish, and finish with Flitz.  

Anyhow, knowing what grits you are working with is pretty important with polish, yet I couldn't find anything that actually said what grits where in these.  MSDS doesn't say contents, so I did more googling.  First off, I didn't know this one, but wear gloves when using all three of these.  Seriously.  Pretty decent solvent content of kerosene, alkaloids, ammonia, naphtha, etc. 

All three have friable aluminum oxide in different amounts and size, so they break down and get finer and finer as you polish.  Sizes are based off googling btw, from other discussions where people called the manufacturers, etc.  Micron to grit is ballparked off the Gesswein Canada conversion chart.  Mind you, take this post with a grain of salt, as I am not a materials engineer.  Also make sure your compounds work with what you are polishing.

Simichrome is around 10 micron, so ~1800-2000 grit
Mag Polish is around 4 micron, so ~5000 grit
Flitz is 3-3.5 micron, around 7-8000 grit

I'll tell you what though, going through those three in that order with a light touch will turn parts into mirrors.  If there are surface marks, you'll still have them showing even if the surface is smooth, as you have to start with the scratch/mark's grit and work up.

But if you just want a smooth surface for something, they work great.  So long as you don't go nuts with it, they won't change dimensions on parts with a light hand behind it.  Smooth the surface, not cutting it is the whole point.  I recently cleaned up a RIA 1911 for my dad this way.  Functions 100% BUT I also understand what I'm doing.  Dicking around with polish compounds without understanding what/why/how to use them will end up with screwed up parts.  

While I can smooth out the odd part here and there, I don't consider myself qualified enough to even consider doing a whole gun.  So grain of salt on all this. 

Thanks!  Wish this was pinned somewhere.

Yup.  But at least getting the info out there is still useful.  Kinda was a pain in the ass to look up. 

You can also purchase .25 micron diamond concentrate spray for only $19 .25 micron diamond spray That may seem expensive but a little goes a long way. Also it isn't that much more expensive than Flitz.

Huh, I didn't know that. While I personally wouldn't use it on gun stuff, could be nice on knives. 

I just realized that was 120,000 grit.  Holy hell. 

Also, it's discontinued.  Will see if I can find it elsewhere.

I spray it onto a piece of watercolor paper or balsa wood to polish and hone straight razors.

http://www.handamerican.com, the supplier is moving at the present and is closed. You can get this diamond lapping kit for $12.13 +s&h.

Try cerium oxide or tin oxide sometime.  Use a flat leather lap with a cushioned back and mix the powders into a slurry.  Run it wet and start at low RPM.  Metals are soft and polish FAST.