I have not tried a Winchester breech block but from experience of shooting .32 rimfires reloaded with .22 blanks in Remington and Hopkins & Allen single shots the firing pins are big enough they will hit a .22 good enough to set them off. ( I am making my rimfire cases with the .22 case centered, not offset). Put some marking compound like Prussian blue on your firing pin, put an empty .32 Long or short Colt case in your chamber and mark the case with the firing pin. Then center a .22 case on the .32, rim to rim. See if the .22 case overlaps the firing pin mark.