Recently I had cause to breakdown a large amount of ammo collected in our 'duds box' at my club.
I took the opportunity to segregate the .22RF bullets and melt them down to measure the hardness. Reading on the Lee tester came back at 8.2BHN, a shade harder than I was expecting and close to 40/1 alloy.
Ammo was a wide variety of brands, subsonic, standard velocity and HVHP.
Cheers from New Zealand