Regardless, the original barrel should screw in, and when aligned with the front sight vertical, the cylinder gap should be whatever it was before. Use anti-sieze compound on the threads, it helps. Hold the barrel in a strong vise with wood blocks grooved to capture the barrel. Resin helps hold from rotating, which could scratch the barrel. Use a length of hardwood 1x2 or so to turn the frame inserted diagonally through the frame's cylinder window, you might adjust the angle of one face of the wood to make flush contact with the frame top and bottom so as not to put a twisting force on the topstrap, since the lower frame is tapered toward the front.
