This is not about exactly what you are thinking of doing, but you can use it as a data point.
I originally tried CAS with 44-40's using a Marlin 94, Rossi, and a couple of Ruger Vaqueros. All were new production in the early 1990's. Because of problems with the Rugers, I abandoned the 44-40's. I gave my son the Rossi and one of the Vaqueros and put the Marlin and the other Vaquero into the safe for many years.
The Marlin 94 had microgroove rifling and measured 0.430" to 0.431". Fortunately, the chamber was also big enough to take 0.431" lead bullets. I never did find a load that would shoot well in both the Marlin and the Ruger. About 6 - 8 years ago, I was thinking about a house defense rifle. AR-15's were higher than heck back then and besides, they are ugly. So I started thinking about the Marlin 44-40. I also ran across a bunch of jacketed Remington 44-40 bullets. I worked up to 18.0gr of 2400. The recoil was reasonable and it was accurate. I tried them in the Ruger and found that it was reasonably accurate in it, probably because the bullet is 0.426" - 0.427" in diameter. Of course, the bullet would not be allowed in the competition you have in mind.
I have fired between 300 and 500 of these rounds through the guns (mostly the rifle) since then without problems. That is not a lot, but if the pressure is kept less than a .44 Magnum, the new rifles should take it. Keep in mind that both of these guns are also available in .44 Magnum.