Seems as if I've rain into my first "real" problem. After drilling all of my holes for the receiver, I temporarily dry fitted the rails by sliding the center support bushing and rivet through. I intend on screwing the rails in since I don't have a welder. After dry fitting, I noticed a very small but obvious gap in the heigth of the lower rail in relationship to the plane of the notch in the front trunnion. I would estimate the drop in the lower rail to be about .05'' below the trunnion notch. Unfortunately, the rails I got from TAPCO have predrilled holes for the center support and hammer axis pin. Since I drilled both of these holes before I fit the rails, this means that my holes line up fine, but my rails sit about .05'' below what they need to. What kind of tolerances am I dealing with here? What would be the best approach to resolving this problem? Buying a different set of rails that didn't have predrilled holes? If this were the case, I could just move the rails to the correct position and use the existing holes in the receiver as a guide.