I answered you personally by email, but this answer is good information for all casters so I'll answer again here for the public.
You are talking about only .002 clearance, and rifling depth averages about .008, so the checks will lock on firmly and do their job if you shoot these bullets. However, handling during sizing and loading is a hassle you don't need to live with when LBT is stamped on the mold, so if you return it I'll fix it N/C. - With the oversize bullet we are working close to max diameter for these checks, so after I increase the shank diameter, you may have to press the checks on, and positively will have to if the mold isn't held firmly closed with every cast. An easy fix for checks which almost hang on like this, and if the bullets perform properly, is to put a tiny smear of bullet lube on the base of the bullet before seating the check, to hold them in place while handling.
Don't do this with bullets for bottleneck cartridges if the check is seated below the case neck, as they will fall off into the powder and cause leading and inaccuracy with the bullets which lose their checks. - The check will exit the bore without harm but may fly wildly sideways in flight, and could be dangerous under some condtions.
