You bought "wooden blanks". They were blanks loaded with wooden bullets. The threaded muzzle commonly seen on the Swedish Mausers was to allow the attachment of a "blank shredder" which basically turned the wooden bullets into tiny splinters. The idea was that soldiers could practice the basic motions of loading and firing without needing a dirt backstop.
Just a warning, they MAY have corrosive priming--it's been awhile since I've read anything about them. Also, without the blank shredder, the wooden bullets will exit the muzzle at significant velocity, so treat them with respect even though they're called "blanks".
What I was trying to buy was steel dummy rounds. Solid pieces of steel machined into the shape of a 6.5.x55mm round.
In addition to the steel dummies and the wooden blanks, at one time you could also purchase "gallery" ammo in 6.5x55mm from Samco. The rounds were loaded with very short bullets in front of a light powder charge. I'm quite certain that they were corrosively primed.