I have an early Kimber 1911, pre firing pin safety, bought it in 2000. It has always had around a 4.5# trigger pull, all of a sudden it is around 3#. I have changed nothing and recently did my first detail strip of the gun and every thing looks good. It has had thousands of rounds through it over the years, maybe around 15,000. It still shoots great and is reliable, what has caused the change in trigger pull?