Antler (and bone) have a lot more in them than just Calcium, but it's a major component. Vinegar (acetic acid) would react with the calcium in the bone to form Calcium Acetate and it would give off bubbles of Hydrogen as a byproduct. In as much as commercial vinegar is only about 5%-7% acetic acid to begin with (the rest is water) I doubt that a few tablespoons in the pot will do much. A cup or two might. If you don't see bubbles, there's nothing going on. And, don't use an aluminum pot. You WON'T like what that much vinegar will do to the surface of unprotected aluminum.
You might even try soking the antler for an extended period in a vinegar solution. I remember trying that with a chicken bone with I was in school. After a few days, the appearance of the bone was unaffected, but it was as flexible as rubber. Antler treated that way might turn easier, but it might not finish as well.
Experiment and let me know what happens.
