Those 75 hornady shoot very very well out my 224 Valkyrie. I never shot any 10 shot groups but I shot a bunch of 5 shot groups and I use them instead of the 80 ELD-M that my daughter uses.
So do you guys dont shoot 10 or 20 shot groups in comp. I bought 1000 75gr hornadies last year when they were dirt cheap. I thought you had a load for them in your 223.