Goldenlakepete,the OP is asking specifically about Sellier & Bellot made 5.6x52R ammo
Real 22HP is .228
Some folks get by with .227
Some folks claim that .224 are accurate
I have a box of S&B here someplace 88...if you still need an answer let me know,but I'd guess they are .228 as it's primarily a Schutzen round over there and I think accuracy counts![]()