The liner in my Maverick was labeled, so when i took it out the first time, putting it back it just would not do that, turned out it was the label that had come off, and i had to poke it out of the barrel pipe.
IMO they should have been laser engraved from day #1 not least as i think FX have a machine like that / such a machine not costing a fortune i assume.
Newer do seem to be laser engraved as i noticed that in the video about the new H&N .177 slugs.
As explained with these barrels it dont take a degree in rocket science to figure out the pitch of the rifling, pretty much just take a measuring tape.