That is a patched round ball twist. "The experts say" it is not enough twist to stabilize a conical bullet. Thus the bullet will start to tumble and accuracy will be lost.
A 1 in 10 twist is recomended for bullets. Some mfgs were making Hawken style guns with a 1 in 24 twist that were supposedly combos that shot both well. I have a TC Hawken I built from a kit that has the 1 in 24 and I shoot both round balls and conicals out of it. Workes just fine.
Best thing to do is get the gun and try it. Different powder measurments and ranges. Could be it will work just fine and the "exberts" be darned.
One of the things I struggle with when afield is keeping my rifle clean and in good working order. Small amounts of dust and dirt collect moisture; moisture can freeze rendering your action immovable when you need it most. I have seen this happen on multiple occasions, and over time, I’ve learned the cause and how to prevent this from happening.
The first thing that you need to avoid before going afield is leaving excess oil on the gun. Oil will trap dirt and sand in all the wrong places....