I have a Model 52 SxS that has a problem with its Greener cross bolt. The bolt is supposed to retract all the way when you close the gun, but the "thingy" (that's a technical term, incidentally) on the barrel hits the bolt on the way down and I have to manually push thumb lever to close gun. Seems that about 1/8" of crossbolt stays out. How do I fix this?