Mav 88 with 18" barrel runs without missfires. When I added a used 28" barrel with choke tubes I got misfires. The next weekend I reinstalled the long barrel and ran 25 rounds without a hitch. Today I reinstalled the long barrel to pattern it with full choke and 3" turkey loads. Click, no bang! Retried several times with nothing but light primer dents. It fired the same round with the short barrel, no problem. Both barrels lock up tight in the receiver. There is a gap no more than 1/32" between the barrel lug and mag tube with either barrel. Any ideas?