I think the Quemado Gathering had a rule that the one shot shootoff rifles had to be normal big game or varmint rifles.
Of course "normal" is subject to bribery, and the whims of judges
Could make it any rifle 10 lbs or under, including scope, to keep it objective.
There was also a "Safari Rifle Shoot" 3 fastest shots to a 6" circle at 50 yards, offhand, iron sights only. Must be a African caliber, I think .375 H&H was considered the minimum.
