Today I was shooting my 457 and after 4 mags it just went click when I pulled the trigger. I ejected the live round 3 times and there was no firing pin strike on the primer. Here is what its doing, engaging the decocker will not drop the hammer, I can pull the trigger with mag removed, I can pull trigger with decocker on safe. I was shooting Federal FMJ ammo at the time, did not notice anything strange after the last time it did fire.

any help please