I recently picked up a Sigma .40 and I'm having problems with a pin on the trigger assembly which causes the weapon to not cock when the slide is pulled back.

your best bet is to send it back to s&w. are you sure it is the trigger pin cause something doesnt sound right with your explanation

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sd40 new APEX kit & mag ext.

I figured out what happened. Apparently, the prior owner took out the pig tail spring and the outer spring in the trigger assembly and re-installed it wrong.