I purchased a used henry mini-bolt a while ago and really didn't do much with it till recently. When I went to sight it in and see what it could do...well the best it could do was 6" at 25yrds. Some groups were as big as 16". What would cause this problem...all screws (including sights) are tight. Could the barrel be "bent" or somehow damaged to cause this? There is no visible damage, btw. And short of replacing the barrel, is there any way to remedy this problem?