There are no TIGHT TC barrels that I am aware of. They are .500" or larger. Both Taylor's and Tom's rifles, my hunting companions - in the 70's - had .502" and .503" bores in their TC's. Mine was .500"- I was lucky - I had a tight one and the most accurate of the 3. Of course, TC back then used the same button for all barrels (I expect that hasn't changed, but their QC on barrels might have,) so the 'boys' rifling was even shallower than .004"- what looked like mere scratches in Tom's rifle - go figure. He shot maxi's and had to wrap them in a cigarette paper to get them to stay inside his barrel for the first shot.
The point is, your bore is not too tight for a .490" ball and .015" patch. It will be too tight for that combination to fall to the breech by the weight of the rod - yes - or be lowered without you actually using any force, but if you want accuracy from those 'cheap' button rifled barrels, you need to make it tight. The .015" and a .490" ball will require a short starter as well, but not a lot of force to seat it - it is not a really TIGHT combination. It will not thumb start- however, it should deliver fairly good accuracy with a light charge, up to about 80gr. 2F max -- for a guess. Our TC's ALL shot best with 2F powder and it produced LESS fouling than 3F.
In my own TC barrel, the tight one, with the 'tight' .500" bore and .004" rifling I tested .490" balls and patches from .015" to .025" using 3F and 2F from 70gr. to 110gr. by TC's manual back then. I also tested as the .495" ball with patches to .022" heavy 'brushed' denim I found in a yard goods store in Smithers, BC. I used the same powder charges for testing and found 2F was best, with around 80 to a maximum of 90gr. of it.
By then, I'd been shooting my TC "Hawken" for about 6 to 8 months and had learned about crowning and how the factory crown would not allow a tight enough combination to produce accuracy. An old machinist fellow from Kalispel, Lester H. Hawkes originally from Montana was MY mentor in this. He told me in order to shoot, that I had to use a VERY tight ball and patch combination in that button rifled barrel. He showed me some Bauska Barrels he had, with cut rifling and explained the differences to me. It all made sense and worked. He showed me how to re-crown the muzzle so the patches wouldn't cut and would form with the ball into the bore, fitting tightly and loading without problems. From then on, loading and shooting all day without wiping was my routine. You might actually have to flex a muscle or two to get the ball and patch into the bore - that's the nature of the beast and this sport. If you don't care much about accuracy or having to wipe between shots, then by all means, use a .010" patch. About 10 months after I bought that TC, I put a real round ball barrel on it, a Bauska .50 cal with cut rifling. That barrel was incredibly accurate and I found the .495" ball and .022" brushed denim patch shot incredibly well in it too. That basic combination of ball .005" UNDER and a 10 ounce denim patch has proven itself in every barrel I've used since.
"Here is a piece of .50 cal. TC barrel with the button rifled .004" rifling. It easily loads .019" to .020"denim (8 ounce) and a .495" PURE lead ball using a starter and the palm of my hand as the smacker to punch it into the muzzle. The gentle radius of the crown draws (swages) the patched ball into the grooves, elongating the ball slightly, giving a very tight fit that wipes the bore clean from the last shot as you load it. Thus, fouling does not accumulate, shot to shot, thus loading never gets difficult."
If there is something there you don't understand, I would be most happy to explain it to you.
