I reached out to Patrick Hornberger and he provided the following:
"Apparently, at the height of the barrel business, barrel makers on the Wyomissing Creek brought their barrels into the (Mohn's) store for pick up by wagons, who then took the load into Reading to be shipped by train to Pittsburgh and Philadelphia. I found records which confirmed that process. What we don't know is why some barrels were marked by the barrel factory and sometimes the maker and occasionally "Mohns Store". The vast majority found do not have the store stamped on them. It could be that those stamped with the store may have been bought by the store from the individual makers and then stamped the stores name on them. It was not unusual for hardware/general stores to follow this procedure-think of the early Sear & Roebuck and its sale of guns it never made."
My research adds the following:
Mohn’s Store was opened 1846 by Benjamin and Samuel K Mohn. Mohnton was known as Mohn’s Store initially and was the designation for the post office until the name Mohnton was adopted in 1906. Any gun barrel with this designation would be after 1846. Benjamin Mohn,
Samuel K Mohn, and WD Mohn are part of my grandfather family tree and are tied to Mohn's Store and the community post office. I have nothing on where they participated in barrel making or gun smithing. I have found a long rifle sold in 2009 that was engraved with B Mohn on the barrel.
My family did not discuss history very much so I am trying to follow a weak trail.