S&W 1012 autoloader

[M&P40]

A friend of mine recently purchased two brand new smith and wesson 1000 series shotguns in both 12 and 20 gauges. The 20 gauges has worked flawlessly every time no matter what load he runs through it. The 12 on the other hand not the case. At first when using target loads the guns would fire and the shell would want to eject but get stuck on the extractor while the next shell is trying to load. He then tried hunting loads which worked fine. He disassembled both guns cleaned, oiled and stored until this past Saturday when we went trap shooting. Now on the 12 gauge he had to cycle the bolt manually every time. This was happening with both target and game loads. We disassembled and looked everything over and it appeared to be assembled correctly. These shotguns have an internal drum one is marked target loads and marked field loads. The drum marked field is what was in the gun to start both times. He hasn't used the field on yet. Any ideas would be appreciated.
Thanks in advance

 

[LanceOregon]

The drum marked field is what was in the gun to start both times. He hasn't used the field on yet.

This situation is not at all clear. In the first sentence, you say that he only used the Field piston. In the second sentence, you say just the opposite: that he has not used the Field piston.

????
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[M&P40]

I'm very sorry for the confusion. My bad. The target drum is what was in the gun both times. The field drum has not been used.