Thanks, guys, for you compliments.
For more history on the closing of GRRW and the people that tried to resurrect and reincarnate the company go to my web page
GRRW Successors. If you don't bother to read the whole story, at least scroll down to the bottom and read the last paragraph. It shows how circular life can be.
I think
tenngun, Dutch, and
sawyer04 have addressed the OP's question for "back in the period".
In more recent times, I recall a lot of interest in .52 caliber ML barrels "back in the day" (1970s and 1980s). I know a couple of guys that had some custom barrels made in that caliber. I'm not sure what spurred this interest. If it had been one size up in .53 caliber, I would blame it on various gun writers, but most notably Charles E. Hanson, Jr. and John Baird.
These mid-20th century gun writers didn't like writing the term "balls to the pound" which was the standard way of expressing a gun's bore size prior to the development of cap and ball pistols and the Minie ball for the rifled musket. They confused themselves and the reading public by using modern terms such as "gauge" and "caliber" in place of "balls to the pound".
Charles E. Hanson, Jr. in
The Northwest Gun (1955) erroneously used this table for converting balls to the pound.
In the text introducing the table, he equates "gauges" to the number of round balls to the pound. This only makes sense if he is redefining "gauge" to mean something different than its modern definition. But he doesn't. The table above is correct only for the modern shotgun term for "gauge" and the modern rifle term for "caliber". It is not correct if one equates "gauge" to equal balls to the pound.
Hanson uses the same table in
The Plains Rifle (1960).
You might ask "why is Hanson's tables wrong, they look right to me?" As I said, Hanson's tables are correct if the headings of the columns are viewed as modern shotgun gauges and modern rifle calibers. They both represent the Inside Diameter (ID) of the bore of the gun.
The error is that the old term of "balls to the pound" represents the Outside Diameter (OD) of the round ball. Now any experience shooter knows that if you try to load a patched round ball that is the same OD as as the ID of the gun's bore, you likely will need a mallet to get the ball started (which some target shooters do, but not most casual shooters). We normally shoot a round ball whose OD is 0.005" to 0.010" smaller than the rifle's land-to-land ID or the smoothbore's ID. This difference in ball OD and bore ID was called "windage" in the day. It was space allowed between the ball and bore for patching material and the buildup of fouling. In military smoothbores, windage could be as much as 0.050 of an inch. Civilian rifles generally had much smaller amounts of windage--on the order of 0.015 of an inch.
Referring back to Hanson's tables, a rifle that carried 32 balls to the pound would be equivalent to a .54 caliber--not .53 caliber. How do I get this? You have to go through the math using the density of pure lead to calculate the OD of a ball, the size of such that 32 of them would weight a pound. The calculations show that the ball would have an OD of 0.526". Now add the windage of say 0.015", and you get the bore ID of 0.541" or a .54 caliber rifle.
Essentially, Hanson's table isn't taking into account the need for windage. If his "Gauge" represents "balls to the pound" as he says, then his "Caliber" is giving the OD of the round ball (rounded off to the nearest hundredth), not the ID of the bore.
Many other writers made this same mistake. Baird has many statements in his first book where he equates 32 balls to the pound to a .53 caliber rifle (
Hawken Rifles: The Mountian Man's Choice, pages
xi, 23, and 45).
This could also explain why Uberti made the bore of their Santa Fe Hawken undersized. They were either influenced by Hanson and/or Baird or they independently made the same mistake.
But this still doesn't explain why the interest in the .52 caliber back in the 70s and 80s.
Just one final comment. The surviving American Fur Company records show they often ordered trade rifles "32 to 40 to the pound". Assuming a windage of 0.015", that would mean their typical trade rifles were .54 caliber and .50 caliber--how convenient considering those are among the most popular ML calibers today.