I could be partly to blame for this. Because Mr Chip Shoulder thought you were a mod and he could not post anything else on the thread he sent me a PM.
This:-
I checked that just now, there was some play I could see and feel, but it wasn't exactly slopping about. Having just reread your comment, I only checked one cylinder !!! Bugger!
I did take a video of the one cylinder I checked. There were also marks on it that looked like cleaned up rust pitting and vice clamping marks! Also the metal was marked a bit around the nipples as if the cylinder had been catching as it rotates? This can also be seen in the video.
So not sure, I expect no, I see that HK also have one in stock at the same £400 price.
I sent this reply:-
Hi, You can sometimes expect a little bit of rust on an older gun, especially blackpowder, so long as it is not deep and appears to have been badly neglected. I would be wary of any gun with vice marks. Why has it been in a vice? Anyone who is competent would have used lead sheet or thick leather to clamp it up to avoid damage.
The nipples should not be binding anywhere. You do get a line on well used pistols where the locking pawl drags along the cylinder between the locking lugs while it is rotating, but that is normal.
I cannot decide this for you I'm afraid it is up to you. But from what you have told me I would look for something else.
I hope this helps.
It might have been better if he had started a new thread with the question about the condition of the gun and what to look for.