I just purchased a Western Field model 550AE, essentially a Mossberg 500. I have disassembled and reassembled the action twice. The problem I have is that the slide assembly will not come out. Something is blocking the slide action arms. They will not come straight forward out of the frame as the 500 does. I want them out because the slide action is stiff and the arms must need a little judicious honing. Can anyone help? I have sent a request to Mossberg service but no response.