We have a local shop that sells aircraft-grade stainless rods. I have no idea what the #'s are for this material, but I bought a 48" 5/16" rod of it, drilled and tapped one
end for jags and brushes, and epoxied a wooden handle, a piece of birch branch on the other end. This is useful for cleaning my 44" .50 bl., however, until I started using
'range' rods, I simply used the rifle's rod - for a couple decades, actually. they always worked just fine.
In Jim's video - WOW - that skinny long fit!!!!! shocked I am, but shouldn't have been. I believe even I could build that kit.
Now I just have to save up some sheckles.