My dad had a bunch of old muzzleloaders when I was growing up. He taught me how to take them apart and reassemble them. I remember him telling me pins go “in from the right, out from the left.” That was his habit, although now I don’t think it was a universal practice. We know that original Hawken rifles had the barrel wedges inserted from left to right, for example.
I don’t remember peened pins on any of those old originals. Not on the barrel pins, anyway. I don’t think I ever tried to remove ramrod pipes, but as far as I know, those were permanently installed, and the pins were meant to be unobtrusive. Peening the ends would make them larger and more visible.
I can’t think of a historical precedent for peening the ends of pins for barrels or ramrod pipes or triggerguards. I think the “return” on the buttplate of some old smoothbores was also pinned, but I don’t recall seeing one peened.
I can think of reasons not to peen the pins for barrel lugs and mountings, but, respectfully, I don’t know of a practical reason or any historical precedent for peening them.
I’ll admit, I learn something new every day, but I don’t think I’ve ever heard of this before.
Best regards,
Notchy Bob