Welcome to the Bersa Pistol Forum from The Lone Star State.
On your problem, does it happen when you fire the BT380 SA or DA or does it make a difference??? Is it a new gun or is well used. When do you let the hammer down with the De-cocker?? What I mean is do you insert a full mag in the BT380 with the safety off, then rack the slide to chamber a round which will leave the hammer in the ready or full back position...??
My Bersa 380 will double-click if I fire it or if I dry-fire it. I bought the gun used, he said he had fired 4 or 5 boxes in it.I insert a full mag in,rack it to chamber a round then hit the de-cocker to let hammer down. I have never had it jam, but it will do this double-click sometime. Thanks.
If the person you purchased your BT380 from only fired 4 or 5 boxs thru it, it is barely broke in yet so it may not be a major problem. I have never heard the double clicking sound however I would recommend that you take you BT380 apart, remove the grips and do a very good cleaning and lube job on it. After cleaning and lubrication, with the grip removed dry fire it and check the operation of the Hammer, Hammer spring and Hammer spring guide. That may be where your problem is. I hope so.
I tend to agree with Tony. Disassembly so that you can look at the gun may prove very helpful. Who knows, you may even see something that is hitting, rubbing or whatever before you do anything else. Just look at everything carefully and clean and lube. Seems the grips on Bersa 380's give some problems moreso than a lot of other pistols. If they're too tight, they rub and cause problems. Might cause clicking, I don't know. Dry fire without the grips on may also give you some answers.
So do a careful inspection and cleaning. Lube it and make sure everything is free. Grips not too tight and go shoot that baby! One question: why drop the hammer after initial loading? Don't want the first shot to be SA for some reason? Don't know that that has anything to do with it, more curious is all. Good luck with your project!