Was this a new Cooper? I would be a bit concerned about a Cooper that shot 1 1/4 inch groups. Everything tight? Bore good and clean? I shoot 36 grains of Varget and a 52 grain Berger in a Tikka and get real good results, you might try that. You might list what combo's of reloads you have tried, maybe a niche there.
Mankind is suffering from random stupidity.
An armed man is a citizen, an unarmed man is a victim.
Only those that understand what we can lose are willing to fight for it.