I have never heard of a T/C Renegade barrel that had a bore diameter of less than caliber size. if the land to land diameter is .525, as you indicate, I would be contacting T/C to ask about it. The .545 Groove diameter is much less than most T/C .54 barrels will mike out to. Perhaps you need to take it to a gunsmith, or local machine shop, and ask someone there to take those measurements. You have indicated that you are not that confident in your own abilities at using calipers.
Another member of this forum also was not sure of his ability to accurately measure the bore of his gun, so he stopped by my home one Sunday, and we measured it together. I also gave him some instruction on how to use that caliper to get precise readings. He had not been holding the caliper right, and it was tipping in the barrel, giving him false, and " short " readings.
The others are correct in advising about those T/C maxiballs and the Great plains hunter bullets. Thye are stepped, so that the last band, closest to the nose of the bullet, is about Groove diameter. It takes a good whack on your short starter to seat those bullets in the muzzle, because the lands have to score the driving band on the bullet, to let the bullet go down the barrel.
I am much more concerned about your comments about how difficult it is to push a PRB down the barrel. If your bore diameter is only .525, then a .530 ball and patch will BE Difficult to seat, even in a clean barrel.
Don't run balls and bullets down the barrel with a mighty heave on the end of the ramrod( That is how beginner shooter break wooden rods, often injuring themselve in the process).
Use a hand-over-hand method, with your hands never being more than about 8 inches apart, and the heel of your bottom hand right at the muzzle, guiding the rod straight into the barrel, so the rod does not scrape the crown or the lands as it goes down the barrel. Using this method will let you feel the condition of the bore as you run the bullet, or PRB, down the barrel.
The only time you use a rod to take full strokes, is when REMOVING the rod after seating the barrel, or when cleaning the barrel, preferrably using an Range rod, with a muzzle protector.) Even with this limitation, use your other hand to put your index finger and thumb around the rod at the muzzle, to center the rod, and keep the ramrod from touching and rubbing against the barrel as you pull it out of the bore.
Yes, the hand-over-hand method can get your hands, and everything else dirty, if you don't take soap and water, and some towels with you to the loading bench. But you want to clean that rod, and muzzle protector after each use, anyway( to remove grit and powder residue that carries it), and the towels can help keep your hands clean for the next shot. In the field, you just aren't going to get lots of shots, so you aren't going to get very dirty, there, anyway you go. ( I still take an old terrycloth towel in my daypack when hunting big game. It stays in the car with water, and soap, in my range box, when I am bird hunting, or hunting small game.)
