Yep, got to be careful with vintage (or even sometimes newer) double rifles. There are any number of problems which may exist and which will often be difficult for the uninitiated to diagnose. And, when encountered, sorting the matter will become costly. After all, it isn't a Remington 700 for which you can simply order a part from Brownells.Been there - done that.
An equally perverse obsession is the gun or rifle that is a bargain and just needs a little work .......
Initial investment, at the neighborhood gun show, in a Birmingham SxS whatever rifle in 450 something or another - $3200 - absolute steal!
Take it to the range with Hornady DGX's in hand (because they are the only quick commercial option available) - right barrel fires - left not so much. Doesn't really matter because the bloody thing won't open after firing.
Call the local gunsmith and he won't touch it (smart guy). Suggests I send it to some character half way across the country whose name I can't pronounce.
Ship it and three months later get a call - sounds like Colonel Klink. Rifle was off face which was the issue with opening the action - can be fixed for only $300. Left barrel not firing properly was due to a broken spring - that too can be fixed for $500. Had I noticed that the rib was no longer properly attached to the barrels? Fortunately, that too can be fixed for $1100.
Six months later, rifle returns home - now a $5100 investment. Back to the range with Mr. Hornady and we fire a L/R x L/R at 50 yards. I have seen smaller improved cylinder patterns of number six shot. Also, after round number 4 their is just a hint of wiggle where the pistol grip meets the frame.
Fortunately, I don't reload - see Rvoni above - so I call the guy with the funny name again. Rifle is mailed the next day. Some weeks later I receive a phone call. The wiggle is due to the head of the stock being saturated with several generations of oil. Really not salvageable. The Nazi gunsmith can build me a new stock and supply a serviceable blank for only $2500. HOWEVER, the barrels have clearly been re-soldered at some point. Yes, he had suspected that when the rib problem was identified, but one never knows until rounds go down range. He is happy to try to work up a load that might by some miracle regulate (for a nearly unimaginable sum of money), or he can re-regulate the barrels (and, of course, re-do the rib) for Mr. Hornady's ammunition for $1400 - 1600 depending upon how much range time is required. At this point I can either use the bloody thing as a tomato plant pole or drop another 4 large.
Eight months later the prodigal gun returns home. It shoots! The stock is lovely and fits perfectly. Regrettably, the barrels and action now look like faded, worn sheet metal in comparison. And then there are those buggered screws (pins as the Brits say) holding everything together. I call some guy in the rust belt who specializes in case coloring and we discuss re-coloring the action and rust bluing the barrels - he tosses out a number that sounds a lot like $1200. Several weeks later, I receive a call. Cleaning and prep will be a $350 add - and wouldn't it be a shame to do that wonderful case color work on worn engraving. That can be "picked up" for only another $650. Nine months later the rifle comes home and it now represents an investment of something over 12 THOUSAND dollars........
On a really good day, at a really good auction, I bet it will fetch $8500 before a seller's premium. It's a fine madness.