And pellets are like clothes. In Marks and Spencer a 36” waist is different to a Matalan 36” waist.
My German guns all like AA Diablo Field 4.52. They fit nicely. So since people here rave about H&N FTT, I bought some of them in 4.52. Same head size, practically had to force them into the breech, and grouped like a shotgun. I suppose AA 4.52 is H&N 4.51 or 4.50, but I didn’t try any further experimentation.