Our club has the open class (20 fpe,) international class (12 fpe,) and hunter class.
Hunter class: shooter can use spring or pcp. 12 fpe. Bipod. Prone. Short stool. No greater than 12x scope and no clicking. Non adjustable stock. No match trigger.
This is a general and rough representationof HFT as there’s only a couple of guys in my club shooting this class. The majority of us are open class pcp.
Just about everyone shoots .177 because the smaller the projectile, the more space there is to knock downa target.
That means your margin of error is a few thousands larger. A smaller pellet fits thru the target hole easier, theoretically.