Got a buddy that has a Ruger Mark I, likely from the very early 1980s. It's got a ringed barrel. You can't "see" it when looking at the pistol, but you can easily feel it when you have a patch in the bore to swab it.
Doesn't affect accuracy whatsoever. Certainly doesn't affect safety. We know it's there, but that's the sum total of it.
Attention Brass rats and other reloaders: I really need .327 Federal Magnum brass, no lot size too small. Tell me what caliber you need and I'll see what I have to swap. PM me and we'll discuss.