The Aqua Regia acid mix will work. It'll disolve platinum too,,maybe palladium.

I think it's a 3:1 ratio mix but I don't remember which is 3 and which is 1!
Doesn't matter, as garbler says,,it's nasty stuff and will pit the base metal if it's steel as in a gun part and very quickly.

Also, these days, it's expensive to buy (and usually hard to get) common acids in most any quantity and lab quality.

Then what do you do with the mix and the remaining unused stuff you bought after trying to strip the one part.
The A/Regia is very unstable. Mixing the two can be an adventure.

Best bet if you don't have or want to set up a de-plating outfit (I think you need sulfuric acid in that) is to send the small bits to a professional plating shop.
Let them deal with EPA side of the disposal of the chemicals from the processes.

Another good plating source that can handle de-plating as well is
Reliable ElectroPlating in Chartley, MA.

Been around about 90yrs. They have an FFL and do firearms for quite a few engravers and gunsmiths.
Lots of other specialized plating as well.
I've used them for the last 30yrs and have had zero complaints.
Custom Gold & Silver Plating, Antique Finishing: Reliable Electroplating: Chartley, MA