Originally Posted by Donn
In addition to what C3 said, I understand the other difference is in the barrel. 223 is a 1/7 twist, 5.56 NATO needs 1/9.
Sir, this is not correct.
it depnds on the weight of bullet and we've gone over this.
1/7 is the milspec because they wanted to keep the option of shooting very heavy bullets like 75gr and higher .
But cptrary to internet rumor 1/7 it is not even neccessary for the standard 62 gr military round which is equally accurate in a 1/9 barrell.
Personally I feel that 1/9 is perfect for our civilian purposes since it shoots 55gr and 62 gr equally well and can handle up to 69 gr someitmes more just fine.
And in any event 55gr is the most common civlian bullet.
1/7 is considered more prestigous by many since its the milspec..
And of course some folks DO shoot the heavier bullets like 75 gr, 77gr etc those folks should go w/ 1/7.
My AR's are amix of 1/7 and 1/9 BTW but since i limit myself ( for now) to 62gr and 55 gr bullets they are functionally identical to me ( 55gr also works fine in 1/7 barrells even tho theoretically it should lose some accuracy being "over stabilized")
but all this has nothing to do with .223 vs 5.56 and c3 shooter explained that properly IMO.