6It may or may not be a drop-in, There was a bit oif fitting on mine between the cylinder arbor and the barrel's arbor hole size. Also suggest buying wedges and screws for each barrel, fit the wedge and keep it with the barrel. I tested for fit between the frames and barrels, and started with the best fits each. now I have two frames that can mount 38, 44 and 45 barrel and cylinders.
The most important fit is headspace. Start with the height of the rachet FIRST. fit for about max. .006 over the case head to breech, and check with a few different brands of cartridge cases. (Overall, unloaded, .062-.067 for 44 and 45,, .060-.066 for 38.) The rachet teeth need to be stoned a bit, keeping the six faces flat and even if the headspace is exsessive. Then, only after the headspace is correct, fit the length of the gas ring until there is .001-.002 endshake with the wedge set correctly. The wedge should be set so the face of the clearance cut is against the retaining screw'sa inner face. Set the wedge in until the screw will turn into the cut, then drift the wedge back against the screw. This is the proper position. If you don't think you can do it, or don't have the tools, let a gunsmith do it.
With the endshake set so the cylinder is not pinched, the cylinder gap will be nominally correct.