make sure you clean out the cylinder throats and barrel with a choir boy wrapped around your brass brush chucked in an electric drill to remove all the leading that may be present. or, use a Lewis lead remover.
I'm guessing you have a leading issue. or, the other problems already stated.
I had a model 14-2 that had similar issues. turned out the barrel/cylinder gap was .006 on one side, and .020 on the other. shot monumental groups until I had the barrel forcing cone recut and the barrel turned back a turn to give me a constant .003 gap.