I'm fairly certain the M18 & the Sauer are exactly the same rifle other than branding. We never found out if the Barrel is threaded or a pressed on affair.
Yes they are identical actions and barrels, the only differential is the stock composition. Barrel/action interface is threaded.
I believe the mauser had different style tenon, like a press friction fit. Whereas the sauer is actually threaded.
That would be incorrect.