A buddy has a Pedersoli sharps long range target. This is one of the older guns made right. He wants to make it a 45/100. I said shoot the thing as is but he wants a big boomer. What say you boys is it doable problems comments?

It would have to be a reamer that would clean that Pedersoli chamber up, so the demensions of the existing chamber would need to be carefully measured and the 100 reamer be spec'd for that existing chamber.
Best bet all the way around would be a rebarrel and chamber.

I used a throating reamer to lengthen a Pedersoli 45-70 to a .45-90 by hand with a T handle and it cleaned it out fine and shoots well.
If you go this way make sure the pilot is a proper diameter and make a bushing that supports the shank in the rim recess to hold it centered.
.45 throating re. by Kurt, on Flickr

That is very interesting by hand never gave that a thought. I have read of folks doing 22 hornet to k hornet by hand. The throating reamer can it be used to go to 45/100 by setting the bushing to the proper length?

PAshooter, This reamer I designed and had ground to my specs. I only shoot a PP bullet mostly but I also use the GG. This reamer has a 5 degree/2.5 degree compound transition to take out the .now standard 45 degree chamber end to make a gentle transition into the throat like the rifles had in the 18 hundreds. In my opinion the 45 degree wall at the chamber end does nothing but shave lead and paper.
To this point this reamer has been used 23 times as far as I know for sure and I have not heard of one rifle that has been changed shooting lead bullets that it had negative improvement.
To answer your question on how deep one could go, you can make a 2.1 into a 3.25 or deeper if you want.

Thank you for that info makes perfect sense about the chamber transition. We have a few BPC shooters in my area who are into PP, custom molds, and so on. I believe I will see if they will share their knowledge. As I said this is a friends rifle if he decides to do the rechamber i want to give him the best input i can. I shoot a 45/70 and am just getting the bug to look at PP I will remember your advice on that reamer thank you again.

I've had 45's from the 2.1 to the 3.25 case and my experience has been that once a fella goes longer than the 45-2.4, (45-90 case) fouling control becomes more difficult and important. It is certain the fouling can be controlled but maybe I'm lazy and didn't like doing it. My thought is try the 45-2.4 case. I can get 80-85 grs. of 2F in it and under a 480 gr. bullet is plenty for any game on the NA continent. I have no doubt an accurate target load could also be worked up but for that work I use my 40-2.5 rifle. Even in a 10 1/2 lb. rifle sitting behind a long string from my 45-90 would almost cease to be fun.