Only prevalent in the PRC cartridges .Something about the original Saami drawings.
I rented the reamers and did all my guns in about 1 hour with the tool provided by the renter.
I did my 6.5 ,7 and 300 prc rifles.End of problem go enjoy life.
Really fellas it is the easy button.
For more info look up Alex Wheeler gunsmith.He came up with fix and gave it to the shooting community.
Just a finish reamer and extension with some cutting oil,,all provided by renter.
Before this my 7 Prc was the most frustrating dam gun.I tried all the different brass and a couple of those stupid expensive sizers,,,Fail
Ream it once and never even think about it now