Model 12 winchester assembly??

[.300 Weatherby Mag]

So what's the trick to reassembling the winchester model 12 shotgun... When I pull out the trigger group for cleaning, I cannot get the gun to function once I reassemble it... Specifically the slide jams.... I've taken it to smiths who walk out a couples minutes later with the gun fully functional and wont tell me what I did wrong or what I need to do different... What am I missing here???? Thanks for the help...

[Hammack]

Pull the trigger assembly out with the hammer still in the cocked position. Also the bolt needs to be fully closed when put back together or else it can cause problems like you describe.

[omeas]

Could use some help along these lines. Took my 12 apart to install a new beavertail forend. Put it back together, I thought, but it wouldn' function at all. Took to local gunsmith who put back together, but now it jams when I slide it back and it is difficult to rack forward. He says to keep shooting it and it will improve. Not sure I want to do that, but I am stymied-anyone have any suggestions or should I find another 'gunsmith'?