Well, it's all a matter of personal preference but a singleshot with 22" barrel is already shorter than a bolt gun with 18" barrel and that is short enough for me. For a "stalking rifle" I like light weight but find that a longer barrel greatly improves the balance for off hand shots which are often encountered in that use. I'd second the vote for a .223, either standard or super lite. My personal rifle for such use is an old Savage M-219 in 30/30 and I've never found the 26" barrel to be a problem.
CoyoteJoe makes some good points!
I don't understand what to me seems "fad-dish" when it comes to shortening barrels.
As already stated, some cartridges work well on various length barrels, but others absolutely must have enough inches to bring them into their real or FULL potential,
IOW - to function the way they were originally designed to!I think the .204 Ruger is one of those! And other rounds might include the .264 Win Mag, 7mm Rem Mag, .300 Winchester and the .25/06.
Besides the .204R I'd also never shorten a .22-250 or .220 Swift!
However, a smaller capacity case like the .221 Fireball necked to .204 or .192 calibers in a 18 to 20in barrel would probably work much better.
There's a thing called "expansion ratio" when looking at how well and
efficient a cartridge shoots.
It should be fairly easy to see that compared to the .204 caliber and the large case capacity for that size of bore, a .204 Ruger burns a lot of powder, and needs a long barrel to burn it all.
If one looks at the Bullberry website (for custom Contender and Encore barrels), Fred there conducted some tests to calculate the optimum necessary barrel lengths to maximize the ability of the .204 Ruger (and also the .17 HMR).
Take a look at that site and it will probably include what a .204R will do with a 18in tube. Twas me, i wouldn't do it.
If I needed a really short walking or "packing" Handi-Rifle, I'd stick with a .223 on a barrel no shorter than 20inches (in a Handi-Rifle). Overall length of such a rifle would be less than 36inches! Just how "short" is needed?
Heck the NEF "Survivor" with a 22inch .223 or .308 heavy-barrel is 35 1/2 inches out of the box. With a standard L-O-P stock, that rifle would still be shorter than 37in before the barrel was cut.