gun problems

Question
I put the slide rail back on my sigma series 9mm after I oiled it but didn't put the spring or barrel in it now i can't get the slide back off. I have tried the rack it back half way and squeeze the trigger standard breakdown but no luck. PLEASE HELP ME. I'm totally kicking myself for this one.

Answer
It would be easier to show you how to do this than trying to explain it with words.

The sear is in all likelihood catching the firing pin protrusion. After drying firing the gun pulling the slide back slightly, HOLD THE TRIGGER DOWN as you try to push the fp protrusion over the sear. The take down tabs on the side are irrelevant, since they catch on the barrel.