you will know it is coming if you bullet impact starts to shift to the left. you will make a site adjustment (thinking it is you that is causing it) and the bullet impact will be right on. a few shots later, you will be hitting to the left again. this will continue until you are either out of site adjustment, or looking for the pieces of the ejector rod housing.
so if you gun starts hitting to the left, beware. if i were you, i would look for an old model blackhawk. the difference in quality is startling.