I have both 1-48 and 1-66 as a matter of fact I have a 1-38 too they all shoot 3 inch groups they do have to be clean as mentioned above and if you have any off center ramrod ware you have to cut a couple inchs off and rebutton the barrel.The big differance that twist causes is in the loads that they require to shoot good;each gun is an individualso their may be some exceptions but in mine the 1-38 takes 70 the 1-48 takes 110 and the 1-66 takes 120 of RS pryodex. Lee