I just spoke to "Ed" at Marlin, who says that, contrary to rumour, Marlin makes Marlin's barrels, not Green Mountain or other aftermarket maker.
In answer to some of my further questions, he said they're:
- button-rifled, but
- not lapped or honed,
- not heat stress relieved,
- not straightened.
These facts imply certain behavior characteristics, but as this is a thread for the source of Marlin's barrels and not Jaywalker's conclusions, I'll stop here.