The .25 cal has a 1/2’’ barrel o.d. and the .177 and .22 cal. have a 7/16’’ o.d. The baffles and shroud are the same but the air stripper and shroud spacer are .25 or .177,.22 cal. specific (1/2’’ vs 7/16’’) You could buy a .22 breech, barrel, air stripper and spacer and use your shroud ,baffles and end cap or you could assemble a complete top end in .22 and just the removal of the four breech screws would facilitate the swap. You might need a scope sited for each breech as POI would be different.
Just bought a new shroud for my .25 for around $23.00. Breeches are around $40.00. Air stripper, shroud spacer, end cap and o-rings for both, screws to secure said parts, 7 baffles, one spring, a .22 cal barrel. The breech is bare so set screws, bolt probe, plunger, stop plate and screw. I would also buy a .187 i.d.poly transfer port from Hill or JSairrifles. Probably looking at under $150.00 for complete .22 top end. 4 breech screws to swap in less than 5 minutes. All parts, parts diagrams and.part numbers are on the Crosman.com website. Have all your part numbers on hand and direct phone order. It’s very easy and the lady that helped me was terrific. Parts come in about a week from NY.
Dennis