The whole barrel length thing is a bit of a myth as far as i am concerned. A friend of mine has a remmy 26" barrel and i own two, a 20" and a 24" and i can state quite catagorically the difference between the long and short version is 150fps.
How do i know? well i made the effort on three seperate occasions to go and test them with a chrono. The 26" and 24" barreled versions returned speeds of 4,250 using a 32grn home load, actually the 24" was marginally faster which isn't that surprising as 23" is the optimum length. The 20" version managed a pitifull 4,100 fps . The 150fps makes no odds at all in the real world. I have shot fox out to 350yds with the "short" one and they just drop on the spot.
My current set up is a n750 on the 20" supervarmint purely for night work and a minox on my 24" supervarmint for day shooting. I have developed another load using 26grn barnes varmint grenades mainly for long range crows etc, these are doing circa 4,400fps. I gave my mate some of these last winter to try and he shot over 40 foxes with them at ranges up to 320yds .
Why do i like the .204 over the .223 etc?. Well for me it's such a sweet shooting calibre. It's very flat, with a 1" high zero at 100yds i can still just put the scopes dot on a rabbit at 300yds and make a good kill. There is virtually no recoil at all so you never lose the sight picture. Contrary to what you may have read it isn't ammo fussy using the powder i do it makes no difference whether you load at the top or bottom.of the parameters they still virtually one hole group.Some rifles may not group with 40 grn ammo as the twist rate in the rifling is marginal for that weight of bullet hence why sierra do a 39grn blitzking. But for me 32grn tramping on at a sedate 4,000 fps+ is where it's at. Both my rifles group nicely with 40 grn but i never use them (no need). If i felt the need for a heavier bullet i would simply use my .243 with my 55grn homeloads which has a similar trajectory to the .204 but obviously carries more energy and isn't half as sweet to shoot.