223 Wylde is a chambering that is supposed to be somewhat "tighter" than 5.56 allowing the safe use of 5.56 and possibly some more accuracy out of 223. I think it may be a little shorter throated than 5.56, but I am not sure of that. you can shoot either 5.56 or .223 in it. http://www.ammo-oracle.com/#diff
thanks Aimless that helps alot I was wondering way I maker would only offer a size that was never heard of but if it shoots 223 standard and 5.56 better than that's good enough for me.Looks like my next upper will be RRA.
The Wylde reamer is designed to give .010-.020" jump to rifling with 69/77gr bullets seated to fit in the magazine(2.250OAL). It's actually a little shorter in the throat than 223 Match. Either one will give excellent results.