There are basically 3 levels of chambering in 22 rimfires. A standard chamber is large enough to contiain any cartridge, 'bentz' chamber and a full match chamber. A 'Bentz' reamer is tighter than the standard chamber but has enough taper to it that although it is tight it will allow the recoil spring of a 22 auto rifle to chamber most ammo. The match chamber is usually too tight to chamber most 22 ammo ecpecially the cheaper stuff. Also match chambers and some Bentz chambers will have trouble with heacily waxed ammo. Match stuff is usually made to tighter dimensional standards and only lightly waxed or even dry film lubricated. The Bentz chamber is larger than a match chamber at the rear but tighter than a standard at the mouth. Both will engrave the bullet to some degree when a round is chambered. The Bentz to a lesser extent(some of these reamers cut a throat but it is such that some ammo may still show rifling engraving. A Bentx chamber may work, depending on the ammo you are using. The match chamber will not allow some HV ammo to chamber. Both will raise pressures somewhat but the 580 series Remington action should have not problem containing them. The Bentz is a compromise chamber and is what I'd reccomend..
