I'm not an expert, but own two, and have handled a bunch more. I've also spent a lot of time researching drillings and O/U guns.
One has to be bit careful with drillings. Price depends on condition, manufacturer, model, proofs and marks, calibers, etc. Like bolt rifles,drillings made by different makers vary in price. The type of action of the same manufacturer can change value.
A couple things you need to look at for a shooter: is it on face, that is, is the barrel tight to the action? What caliber and guage is it. You might need to do a chamber cast and slug the bore. For instance, there are two primary diameters for 8 mm, .318 and .323. There are variations in between. Numbers on the barrel may be diameter at lands, not bore diameter. What kind of shape is it really in. They are like girls with a lot of make up. You need to look at them in good light and you need to have your hormones under control, before you take them home. You can spend a lot of money on one that you won't like in the morning.
There are people on a couple other forums that are really experts on these guns and can provide much better information than I.
If you're thinking about buying a drilling, or if you just want to learn about them, The Drilling Gun by Klups is a great read.
Hope this helps
Bfly
