I have a custom heavy barrel (Bartlien) that has been sitting for years. I do not know what type of action in came off other that it was a custom benchrest action. The barrel is a tight neck. I want to sell it to someone that can use it. How would I know what type of action this barrel will fit?

Measure the thread pitch and diameter. A picture of the chamber end would also show if it was cut for an extractor. The barrel extension length may also help.

Begs the question: why is it off its original action? Lost its gilt-edge accuracy? Round count putting it close to worn out? Never shot quite right from new? Very few good reasons why guys yank barrels off of rifles that perform.

Chamber info, twist and round count are questions that are coming.

And some guys get bored. Might be a bad barrel, or a barrel that wasn’t up to high standards of the owner, or a caliber that wasn’t the latest whiz bang thing going, etc. Hard to tell. There does seem to be a market for barrels, as long as price is reasonable, and you can provide specs.