...... the 600 yard range in long shot competitions.  This bullet as well as anything over 63 gr will require a 1 in 7" or 1 in 8" twist.

The many different brands and types of ammunition for the 223 make it impossible to discuss all of them.  A good rule of thumb is you won't get quality if you don't pay for it. However, some manufacturers will charge you for quality and still not deliver.  Loading your own ammunition is the best way to assure quality and consistent accuracy.  Talking to others is a good source for information, but remember, Just about everybody shoots .25" groups at 300 yrds with any rifle they own.

 All the rumors and reports about ammo are based on facts but most don't get it right.  Yes, steel cases will wear your chamber and other parts.  If you are not in Full rock and roll and don't plan on firing a couple of hundred rounds every week, this may not be an issue for you.  I shoot a lot and don't use steel cases.  They are death to reloading dies anyway.  

Accuracy can be very good in certain rifles with the worst rated ammunition.  55 gr bullets fired in a  rifle with a 1 in 7" twist will never have groups as tight as a 69 gr bullet in the same rifle.  And, a 69 gr bullet fired in a rifle with a 1 in 12" or a in 14" twist will never group as tight as a decent 55 gr round fired in the same rifle. 

Once you have done your research and found the over all length (start at about .025 from the lands then work out to .005"), the bullet weight that fits the resonance of your barrel the best, and the velocity that your rifle "likes" the most, you will be impressed with the accuracy you can obtain.  Remember that consistently made ammunition fired in the same rifle will deliver consistent results.  Remember the grouping is all that is important when testing loads.  Make sure you are firing at the same target point and evaluate the groups.   Constantly adjusting for a bulls-eye makes it impossible to evaluate the accuracy of your rounds.  You can always dial your sights into "0" and apply the ballistic characteristics for calculating the "Dope" for each shot.