Major component replacement (by anyone) is viewed as high probablity the gun has had a lot of shooting, poor maintenance, and/or a major accident. Any of these cast doubt on the condition of the rest of the gun. High quality repair is expensive. So, the market is going to discount any gun with questions about it. Even if you have the gun carefully inspected and it gets a clean bill of health, you will have to discount your purchese price in anticipation of having to discount your selling price of it some day. This market position moves a lot of guns from collector pricing to shooter pricing.
