I haven't had any experience with black powder doubles, but I have shat a .54 caliber hawken and a .58 caliber Zouave a great deal. I think you will find black powder rifles to be quite accurate and forgiving. What kind of ignition does it have? I assume it may be a #11 cap or a musket cap. I think you will have no problem getting reasonable accuracy. I have shot some black powder rifles with horrid bores and they shot just fine. I would imagine fairly close shots are what it was designed for. Post a pic if you can.