One of the more interesting experiments I've made is comparing the same 9.3x62 ammo in a 21"-inch barreled CZ 550 Stutzen (which most Americans would call a "Mannlicher" model) with the 23.6" barreled CZ 550 sporter I've been using for 20 years now.
The biggest lost in muzzle velocity was around 75 fps, if I recall correctly, but one factory load actually got slightly more velocity from the 21" barrel. This was all done on the same day, with the same chronograph.
From this I deduced that the barrel length wouldn't make any difference in "killing power," but would with rifle handling in thick cover....
