I recently purchased a S&W M&P Shield in 45 acp. When dry firing it is smooth, but when it breaks, you feel and hear a spring like sound. This did not occur on one at a store where I looked at them. But did occur on one at another store.
It did NOT occur on 9mm Shield. The guy at the store said it had to do with a heavier spring in the 45 than the 9mm.
I only own one other striker fired pistol ( Ruger LC9s ) which doesn't make that noise or feel. But then again it was a 9mm. if that means anything. I just am not that familiar with striker fired pistols. Any information would be helpful.