As you likely know Marlin didn't classify barrels with a number for the contour. Most fall close to what Winchester numbers are, but not exact. 
Often barrel contours depended on the cartridge designation, and the larger the bore the bigger the outside diameter. But then I've owned some early JM Marlin Ballards in small bores with very heavy barrels too. Seems more likely to see heavy barrels in the JM Marlin marked Ballards than on the Marlin Firearms Co. marked Ballards. The largest Ballard barrels I've seen were mostly on the Montana model and are about what I'd call a #5 Winchester barrel. A few Pacific models also got ordered with a similar heavy barrel.

marlinguy wrote on Nov 6^th, 2025 at 4:26pm:

I bought a Pacific at the Tulsa show today. Full octagon barrel profile with no tulip at the breech end, 32” long. The receiver isn’t rebated, serial # is 33xxx. From what I found in a quick search, that # makes for later production. Any other gems of knowledge you can conjure up regarding this fine piece of history?

cellargun wrote on Nov 8^th, 2025 at 10:14pm:


The highest serial numbers I've personally owned or seen were still under 37,000 so I'd say yours is a very late maybe 1888-1889 vintage. 
Since Marlin considered the 30" barrel as standard a 32" would be I think a dollar more if I recall correctly. Standard on a Pacific was pretty plain wood, crescent buttplate, and straight grip, so anything else is special order. Rare these days to see a Pacific that still has the original wiping rod, and impossible to find one that still has the wiping rod extension that always got lost or misplaced.

The extensions are just like the wiping rods, except only about 4"-5" long. I've never seen an actual extension, but I have an original advertisement for the Ballard Pacific showing the short extension sitting below the barrel. I also own a very nice Pacific with the original wiping rod and was able to scale the extension off the advertisement image. Like the wiping rods, the extension was threaded on one end to screw into the female threads on the original wiping  rod. It was also wood just like the wiping rod, most likely hickory.
This is mine with the extension I made screwed an the wiping rod.
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Notice also that the original thimbles were color casehardened like the receivers were. Something almost every restorer misses when doing a Pacific restoration.