Well believe it or not neither, back when Brno ZKK's were made, Brno used to mfgr. the 3 lenght of actions.
The shortess action permited a shorther stroke when having to cycle the bolt to get a fresh round, this allowed a lighter stock thus a very light package. They used to be made for .308 Win. lenght cartridges(.243 Win.,etc.). CZ has dropped out this lenght of action entirely but rumours are they might reintroduced these in the future.
The medium lenght action allowed .30-06 Springfield lenght cartridges(.270 Win.,etc.). This package gives a bit more performance(cartridge-wise, with a beefier action to boot & bigger stock) but at a ditrimental cost of higher weight & longer bolt stroke. Saddly CZ has taken this action to work with the CZ-550 series, this allowes CZ to lower parts inventory cost.
The longest lenght action are for magnum cartridges: 7 mm Rem. Mag., .300 Win Mag., .458 Win. Mag., etc.( the .416 Rigby action which is even longer). These action are made for high performance cartridges by beefying up the action, stock(which has to be reinforced) these rifle end up pretty heavy for somebody who has to carry one days on end. These go by the CZ-550 Magnum.
Now on the good side: if you have a small car & have to hitch it up with a 27 foot trailer/full load & drive 100 m.p.h. something will slowly let go. On the opposit scale the same is true with actions: an action made for a .30-06 Springfield which has to digest a steady load of .308 Win. is like feeding it baby food.
Hope I answered part of your question,
-Fred-
