short actions are for 51mm length cases (308, 7-08, ..260 Rem, and 243 Win)
The 7X57 case is 57mm long (same as 6mm Rem, .257 Roberts)
The long action is designed for 30-06 length cases (.270 Win, .280 Rem, .300 Win Mag, 7mm Rem Mag, and others. Even though the 7X57 is shorter than the 30-06 and others listed, it still needs a long action. But we aren't talking more than 3/4 inch difference between "short" and "long", here. I think too much is made about the differences in length of throw, and 3 or 4 ounces difference in weight, and how much stiffer the short action is (supposedly making a "shortie" more accurate). Much ado about nothing, IMHO.
Other characteristics of 7X57 include : Long throat, and fast twist rate rifling. Both features were incorporated in the original (1892/93) military design rifle to facilitate the use of the long, for caliber, 173 grain round nose bullets.
The length of the bullet protruding from the case mouth required the throat to be longer than other calibers. The fast rifling twist rate was needed to stabilize the long 173 grain projectile in flight, as it would tumble if fired through slow twist barrels.
With the current trend in 7X57 using mostly 139/140 grain bullets, neither of these "long bullet" features are needed, yet most 7X57 rifles still have them. And, of course, factory loads are still available for 175 grain round nose bullets. To shoot them, you still need the long throat and fast twist rifling.
As a result, my 7X57 rifle has a full 1/4 inch (0.25 inch) throat length, which my 140 grain bullets must jump to come in contact with the rifling leade. Because of this, I pay particular attention to concentricity of my hand loads. I won't hunt with reloads that exceed .003 inch runout. My end result is 1.25 MOA accuracy. Not a benchrest competition rifle, at all, but good enough for "minute of deer".
All in all, the 7X57 is an interesting project. I did have a copy of the book written by "Karamojo" W.M.D Bell, the elephant hunter, but I recently donated it to the local library, so others could enjoy it.
I went to a hunting camp several years ago, and the topic of "What are you shooting?" came up. As many answered "30-30", "30-06", etc, then it came around to me and I said, "Elephant gun - 7X57" They all got a laugh out of that.
But I had the last laugh!
You will too. Find your elephant gun and ENJOY.