I have an antique double barrel shotgun with the measurements of... The right one sizes at 0.76.10" or 49/64" or 19.34 mm Left one is 0.75.10" or 3/4" or 19 mm Both will take a 12 gauge or a .69 cal rb with plenty of room to spare. Being that the barrel is ancient and probably made larger, is the additional room/circumference made for ticking patch balls. I tried a patch and they do snug it up a bit. What are your thoughts. Thanks.