As I understand it, like many other manufacturers, Ruger has gone to a business strategy of keeping low to zero spare parts or finished products on hand in inventory. Only parts going into current production on order are made and shipped out. If you buy a model that is not going to be made in large runs or remade later and something serious goes wrong with a part that defies simple fixes and it is still under warranty , Ruger may just offer you another caliber or another gun of equal original value. They might bend over backward in making you a good deal regarding a part that is safety critical.
If that piece has gained valuebeyond MSRP due to its after market rarity that enhanced market value is not likely not be seen as part of a warranty. And if you have modified the gun and voided the warranty Ruger might just deny warranty responsibility.
wunbe