I recently acquired one of the original 1989 Smith & Wesson Mountain Revolvers. It was as issued, with Pachmayer Grippers on it. Those don’t work at all for me, so I removed them and noticed that, after having been left on the gun for probably a few decades, there were some black stains or residue of some kind under them. I tried my usual recipe of soaking them in Ballestol, CLP, even WD-40 to remove them.
No dice.
Tried gently polishing with Mother’s, and Flitz, but can’t go too aggressive since this is one of those frosted finishes that would not do well with aggressive polishing.
Anyone dealt with Pachmayer bleed-off or whatever you want to call it? Is there some way to get rid of it?

Just guessing, but acetone is a pretty aggressive solvent and it won't hurt steel. You don't want nail polish remover, but actual acetone, without scents added.

Wear gloves and have sensible ventilation and it's pretty safe to handle.

Just throwing out an idea and someone please correct me if I am wrong. But you could try rubbing alcohol or denatured alcohol before the acetone.

I do not believe either of those will hurt steel.

Seems to me that the rubber turned into a kind of adhesive or tar over the years. You need something that will remove an adhesive.

Another option to consider is to heat it with a hair dryer and see if you can scrape it off with a piece of plastic.

I have an 89 Mountain Revolver. It was a mess when I got it. All I ever use on it is Birchwood Casey lead remover cloths. A little rubbing and I was good to go. My revolver looks brand new again, to include under the grips. I have black Hogue grips on mine. The polished stainless still looks factory. Email if you want. I can send you a pic or two.

I'd be trying rubbing alcohol first, then mineral spirits before going to acetone.

I would go right to the “ Goo Gone - Grafitti Remover”. It comtains toluene , acetone , & xylene.
It is known to attack plastics in paint. So it will not attack stainless steel. Other than that ,polishing with abrasives using judgement to stay within the lines. The discoloration will be covered with other grips anyway.

I had an old container of GooGone and rubbed on the “spots” for a bit and they dimmed somewhat. I discovered they were actually pitting, very, very shallow, but in there was the black residue. And it’s not going anywhere quickly.
Not a big deal, but I don’t have larger grips on the revolver anymore, just some Altamont walnut Magnas, which exposes most of the side plates.
Anyway, win some loose some.

Spray oven cleaner may work too. It works on car stuff.

Would Magic Eraser help? This is a semi-solid fine abrasive, and might be more effective as mechanical removal.

i’ve been successful using a “magic cloth” on just this issue. it’s a coconut oil polishing rag. i was skeptical but damn if they don’t work great. i burn them off amazon and one rag works for years if you keep it in a plastic bag or ziplock.

If your wife or girlfriend is the jealous type, fair warning your hands are gonna smell like you’ve been rubbing hawaiian tropic on a hottie.