They look really bad on a traditional muzzleloader!
I have several rifles that were purchased used with aftermarket detachable swivel studs already installed. I've got a box full of slings, mostly military, but I've never had occasion to use any of them.
While detachable sling studs are fairly innocuous, for reasons that escape me at the moment I found them an unsightly nuisance on the buttstocks of two of my Ruger single shots. Once installed, removing the stud leaves an unsightly hole in the stock, so I had the idea to make a filler screw. I cut down a spare stud almost flush, contoured the remaining surface to a shallow dome (chucked into a drill and spun, using files and abrasives) and then cut a slot for a screwdriver and finished with cold blue. If someday I actually need to use a sling, I can unscrew the plug and swap back to a regular stud.
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