... I read once that spikes will go around 22", and average mature bulls go around 24", like Redfield used in their scopes for elk bracketing. Leupold also uses 24", or did a few years ago, for elk bracketing. So did Premier Reticles use 24".
A 28" bull would be a big one, as was stated.
I knew I'd forgotten someone: Shepherd Scopes also use 24" circles for their "elk" scopes.