Replacement base pins are generally used for removing slop, if any, and providing an additional stop to keep the pin from coming out of the cylinder frame under recoil.
I've had over 20 centerfire Ruger single action revolvers, over the years, and never found the need for one.
On a few, however, I have D/T'd the head of the issue pin for a long setscrew, which I adjusted to bear in a dimple put in the barrel underside, to keep an insecure pin solidly in place.
Ruger has added some very nice custom grips to their online store/website - one of which I just mounted on my .45 New Vaquero:
My 4 5/8" NV shoots 200gr Cowboy loads to POA @ 25yds - but I doubt the same would hold true for a longer barrel and/or somebody else's sight picture.
Vaquero .45's had cylinder throat diameter issues, not being agreeable with the barrel bore diameters - but AFAIK the issues were resolved with the NV, as I bought mine new, and have done no accurizing work, yet get excellent 25yd groups with it.
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