Took my Sigma shooting last Saturday, and I'm having an issue with it. As I was firing it, the steps kinda went like this. 1. Insert magazine 2. Release slide 3. Fire round 4. Round ejects 5. Round feeds 6. Pull trigger, no tension on it...as if the slide was never racked. I can re-rack it by hand, and it will fire again...but then the same thing happens. Ideas?