Generally:
Revolvers pre 1890's or so are black powder.
Note the Generally bit there.
There's a pile of one-offs during the period...if you mean collecting old Colts or old Remingtons and such...well, be prepared for sticker shock. They've climbed in value. 20-25 years ago things you couldn't GIVE away are now worth a large downpayment on a park-front condo in NYC. No shit. I remember looking at a REAL Colt 3rd model Dragoon and seeing a $1500 price tag when I was 12 and thinking 'shit, that's a lotta allowance...I dunno...'
Now, I kick myself for not begging dad to give me a 2 year advance on my allowance
And this was in like 1988!
I wouldn't even really consider shooting one, and this is a guy who takes out a bring-back Luger whenever, and is looking for 8mm Nambu for a Jap WWII pistol for plinking. I like using firarms for their designed purpose, but those things (19th century revolvers, especially from pre-civil war to around the Spanish war) I'd clean and preserve.
Just me, though...