I bought a Sears Model 66 12 gauge autoloader from a guy for $75. Cleaned it up real good and it only holds 4 shells, but at least once out of the 4 shells it jams. Looks like when the the shell should be "popped" up into the chamber and its released from the magazine it's not pointed upwards towards the barrel at the end and gets stuck. Sometimes it when it does go in it doesn't get kicked out and the next shell gets jammed while trying to go into the chamber and its a mess. What should I start looking for first?