With the 5.56 chamber it's safer to fire .223 but not vice-versa IIRC?
I do love the Wylde ("wild" or "wild-E" or "will-DEE"?) option and Ruger should have used it but expect it's not "common" enough for the average consumer...
I've always pronounced Wylde, "wild". I haven't heard anyone else pronounce it differently, but like everything else, opinions are sure to vary.
The leade is shorter in a 223 Rem chamber than a 5.56 chamber, so that it will normally be OK to fire 223 rounds in a 5.56 but not the other way around, like you said.
The Wylde chamber is basically a compromise, to the extent that supposedly, it's safe to fire 5.56 NATO or 223 Rem ammo in a Wylde chamber interchangeably. NATO spec drawings sometimes show the case neck diameter as being .oo2" bigger in diameter than with the 223 Rem, and supposedly, it's because NATO specs call for a thicker-walled case. But I've measured almost that much variation between sized necks from different dies.
Other than that, the two cases are almost always shown to have identical outside dimensions. The difference is in the leade of the chamber. The problem (reportedly) is that the bullet in some NATO rounds jam into the lands of the 223 Rem chambered rifling due to its shorter leade, causing excessive pressure.
I don't quite understand this, and I'd like to read a technical article on it. The bullet gets jammed into the rifling every time the gun is fired, and usually before the bullet has completely left the case neck, so I'm not sure what the big deal is. For best accuracy, reloaders often end up seating the bullet to touch the lands. So if a bullet is seated out, say .020" further, it can blow up because the bullet has already started down through the rifling? The "GO"/"NO GO" headspace range is rarely more than .010", so how would the gun go into battery if the bullet held it back .020", and if the bullet is starting its usual path into the rifling instead, isn't that what it always does? So if a bullet is freebore for any distance at all, say .005", the pressure will be substantially less?
Anyway. With the proper gauges, such as Hornady makes, determining maximum cartridge overall length for any specific bullet and leade is possible, easy, and almost fun. Or for peace of mind and simplicity, either go with the ammunition designation as marked on the gun or get a 5.56 NATO chamber and forget the whole issue.
Here's an article on the topic:
http://bearingarms.com/223-remington-vs-556-nato-what-you-dont-know-could-hurt-you/
