This is a question I found on huntingnet.com, and figured you guys could answer better.

"i have a .223 chamber for my ar-15. i have been told it would be a little risky to shoot 5.56 out of a .223 chamber due to the fact 5.56 is of a higher pressure load vs. the .223 load. that being said has anyone hunted with 5.56 and has anyone shot .223 out of a 5.56 chamber? if you have can you tell me if you noticed any accuracy differences say out to 200 m. i may buy a 5.56 upper but am not sure about it if it will throw my groups to hell at 200m. i currently shot blackhills 60 gr V-MAX blue box and love them. hope someone here knows what i'm talking about"

Thanks

The 5.56 chamber has a longer lead and it's been beat to death around here.  Do a search and you''l find threads on the difference.

As far as accuracy goes, the 223 chamber will be more accurate then the 5.56.  The 5.56 will be more reliable if you are going to be firing many rounds of ammo.  I have a bushmaster 20 inch ar with the 5.56 chamber and I can get 1 in groups at 100 yards with the stock rifle, with a scope and handloads.  This is a chromed lined barrel also.

If you want the most accuarcy out of your rifle, I would go with a match barrel with a 223 chamber.  That's in an AR.  I reload all of my ammo so I could work the load up so it's safe in my rifle.  If you plan on shooting surplus 5.56 ammo, I wouldn't shoot it in the 223 barrel personally but that's your call.  Besides, the 5.56 ammo is probility going to be less accuarct then the 223 hunting/match ammo your going to be buying.

Why not let us know what kind of rifle your thinking of getting and what kind of accuracy you are looking for.

This is one of the most often beat to death issues in AR-15 land. I have fired XM193, 3131A, Hirt, SS109, GP90, and SA through a .223 Remington chambered target AR with a SS barrel. I have seen zero pressure signs from any of the surplus 5.56 ammo. If you're using iron sights you will likley see no difference between a .223 and a 5.56 chambered rifle. The only way I can squeeze the absolute last drop of accuracy out of my target rifle is with a scope.