[Wild Skies]

Maybe the barrels don't fit as well on the other gun as you think they do. A thousandths or two of an inch off sounds like an itty bitty, but could make a big big difference in the fit of that beavertail on a precision instrument, such as your Parker Repro. A judicious amount of filing by someone with experienced hands should be able to take care of the issue -- if you're looking to have it fit.