Something to consider..

[EC121]

Just got this one. Sold as a .62cal. rifle. Davis lock. The lock is signed R. E. Davis. It is an early one before they went to the circled D trademark. Unknown barrel with a clean bore. It is 38" supposedly straight, but I measured it tapered 1" to 7/8". Signed DAHoffman 1981.
Well, I went to shoot it today. Upon loading a .60 ball and patch into the muzzle, I had to pound the ball in and just about climb the steel ramrod to get it down. After the shot I went to a .590 ball and .018 patch that loaded fine. I proceeded with the test firing using the .590s.. For a big old jaeger lock it is fast. Off hand I was hitting my 8" steel plate at 50yds. regularly.
While cleaning it, I carefully(that old wood can be brittle) removed the barrel to check the caliber. The barrel is a Getz .60cal. Not a .62. Also the gun was sold as a straight barrel, but the muzzle picture didn't look right on the website. So when I unpacked, it I measured it. 1" tapered to 7/8". Even better!!
You have to watch those auction places. With muzzleloaders half the people in the place don't know what they are looking at. I asked about the barrel and was told it was straight.
It will thump a deer or hog, and a scratch or two won't hurt a thing. It is already naturally aged.

 

[Grenadier1758]

We've probably all been misled by what we believe to be the bore size of a particular barrel. That's why I recommend measuring the bore before getting the ammunition to shoot it. The 36 caliber barrel I carried around for about 39 years turned out to be a 40 caliber. I discovered this when I loaded my first 36 caliber ball.

@EC121, you seem to have one very fine rifle. I would have bought it without much concern for the caliber.

 

[Spikebuck]

That's a beauty!

 

[Jaeger]

I recently acquired a Jaeger rifle and it also had a .60 caliber bore. The guy I got it from was using .590 rbs and I shot it a couple of times with those, but I had to use a relatively thin patch and it was tearing them up. So.....I decided to try loading it with a pretty thick patch and .575 (ie .58 caliber) balls, and it loads and shoots well with that combo.