J,
this is a fairly frequently asked question re the WSSMs, so if you do a search on wssm you'll find several threads.
My sole experience with the design was the .243WSSM in a Winchester 70 Stealth and was not a happy one. I reckon the .243WSSM is a solution to a non-existing problem. It only gives improved performance over the common or garden .243WCF is loaded up to the gills at which point you get
very hard bolt opening. (This applies to Winchester's factory loads.)
Brass is Winchester only, not well made compared to a lot of .243 Win stuff. It is massively thick and so needs very high pressures to obturate in the chamber fully - and I for one hate sooted up cases and a fouled chamber, bolt and action. Barrel life is short. Accuracy is so-so. Factory ammo is expensive.
So far as the .223WSSM is concerned, do a search on .220 Swift. There are a number of guys raving about out of the box accuracy from .220 Swift in Remington VSSFs in other threads at the moment. The WSSM does very little that the Swift doesn't and the same downsides re brass quality and hard bolt lift apply.
The only WSSM I can see that fills a real gap is the .25 cal version as there is no short-action equivalent cartridge except for .250 Savage and that is hardly a commonly found number in modern rifles. .257 Roberts or .257 Roberts AI seems to be making a minor comeback if you must have a rifle in this calibre. If I wanted a .25 rifle (which I never will) I'd get myself a .25-06 - it works very well, and what's an extra half-inch of bolt throw at the end of the day? Over here in the UK, secondhand .25-06s are cheap as they're a minority taste, but most owners love them!
If (rather, when) you burn the WSSM's barrel out, the factory super-short action can only be easily rebarrelled to another WSSM thanks to the combination of a bolt length / throw designed around a 2.3" COAL cartridge and a 0.550" dia magnum cartridge bolt-face that is over-large for the 6BR or similar.
The WSMs are a completely different kettle of fish and make very effective magnum hunting rifles and long-range target jobs. 7mmWSM is the cartridge to beat in long-range F-Class. The shortish fat case seems to work very well and brass quality is much better than the WSSM's as well as having Norma brass available. In some calibres, the WSMs don't do anything that older belted magnums don't - eg 7mmWSM is equivalent to the old 7mm Rem Magnum and .300WSM is a little down on the half-century old .300 Winchester Magnum performance-wise, but not enough so you'd really notice. However, the rimless case is a much better proposition than the older designs' belted forms, fits chambers better, and lasts for more firings.
An easy way of judging these things is to look at the marketplace. Lots of firms including European ones have adopted the WSMs, both factory rifles and ammo, while only Browning makes WSSM rifles now and only Winchester the ammo. These cartridges have not been a success with a few exceptions such as long-barrel hunting handguns in .358/25WSSM or similar wildcats where the ultra-short inch and a half case offers some advantage for one reason or another.
(See:
http://bulletin.accurateshooter.com/2010/03/redding-adds-35825-wssm-dies-for-indiana-hunters/)
Laurie,
York, England