I bought some S&B 7.62x54R ammo 10 years ago because it was Boxer primed, and then had a terrible time seating primers in the brass.
I think that the primer pockets meet the SAAMI drawing for diameter and depth. The problem is the radius in the bottom corner is too large.
I got a Lyman pocket uniformer tool, and that can cut out the corners and make primers fit.
And it is good for cleaning primer pockets too.