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.
Bring them in on a string. I love this term, if you want to be successful on calling in Elk, try not to just sound like the other caller. We all laugh at each other when we are practicing Elk calling at home or while camping. When I first started calling in Elk, I had no idea what i was doing and it's funny how many I could call in. The biggest Bull that I have called in to date was actually my first. I was making cow calls and screwing it up big time. But it's obvious I didn't screw up...