Python barrel on Smith & Wesson

= a Smolt:
https://www.handgunsandammunition.com/revolvers/11070-meet-smolt.html

One source for barrels (also check eBay):

https://www.gunpartscorp.com/search#query=Colt%20Python%20barrel

This is a blued 8" barrel - needs a sight blade also:
https://www.gunpartscorp.com/products/589000