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.
I had the idea of calling antelope, never had heard one before and this was my first antelope hunt and archery one to boot. I know it sounds crazy to most hunters calling a antelope but I just had it in my head that I was going in the middle of the rut and they have to have some kind of vocalization at this time of year. Mention antelope hunting and calling in the same breath, well the old timers thought I fell off the rocker and the bets were on!The knowledge about antelope hunting and...