For those of you who want a .223, including you anti-gunners who secretly now really want one, remember...
A .223 can NOT fire/cycle a NATO 5.56. However, a 5.56 can chamber a .223. The anti-personnel type ammo is most available in the greatest variety in 5.56 as that is the "military" round.
It's like a 38sp and 357magnum. A 357 CAN use 38 shells and most shooting 357 will use 38sp reloads at the gun range because they are cheap. But you can NOT use a .357 magnum in a 38 special (some model revolvers technically will allow it to fit.) The .357 is longer than the 38sp - allowing more powder in the cartridge and therefore a faster bullet (depending on the barrel length anyway).
I bought a used MSAR STG Bullpup - and candidately I am very impressed with design. Taking with a gun dealer, he commeted that was the only firearm of the last batch I bought that wasn't significantly worth more than I paid, maybe a $2-300 more. Then he took that back when he saw it was NOT a .223, but a 5.56 - and included 5 extra 42 round magazines plus strap, and orginal papers and box.
A .223 certainly is deadly - as all firearms are. BUT most consider a .223 a "coyote killer" and it is the 5.56 that is the mankiller. This also is why I found the raging on this forum and the media against the .223 just a showing of ignorance. It would be like raging against 22 shorts, while ignoring 22 long rifle ammo.
Just food for thought if you are in a rush to get your "AR" or other form of .223. It's worth the extra dollars in my opinion to instead get a 5.56. This allows you to shoot cheap (until recently anyway) .223s and even buy reloaded .223 for fun shooting, but have your special magazine loaded with your choice of Nato 5.56s - although I do NOT think the .223 or 5.56 is suited for home defense.,
The Bullpup design is awesome and I'd like one in a .308 - though I think control then would be a real issue in follow up shots and the longer the overall rifle is, the easier it is to quickly sight or impulse fire. Bullpups are for close quarters and tight fitting spaces - but still as accurate and as much barrel for velocity as any other carbine.
If you have the choice and can afford the modest price difference, pass on the .223 for instead a 5.56 - then you can use both cartridges.
Finally, people are so WACKED OUT TO HAVE AN AR15 - even just a bare receive so then it would be "pre-ban" if one comes, and since most don't know much about fireearms to that degree and just keep hearing how bad-ass and likely to be banned the .223 is, there is very little price spread as most don't even know the difference. They are in for an unhappy surprise when they try to run some military 5.56 thru their .223. It won't go.