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Q. Which should I be looking for in an AR15, a 5.56 NATO or .223 Remington chamber? This is really a matter of the role for which you plan to use your AR.  .223 Remington chambers will give you slightly better accuracy, which is important for a match or varmint rifle.  Any loss of feeding and cycling reliability and the restriction against shooting military ammo isn't as important as the accuracy gains for a rifle used in these roles, because for these rifles, accuracy is everything.  People who just want to plink or who plan to shoot military ammo (such as most of the cheap surplus ammo available), and especially those who may use their AR as a weapon, should choose 5.56 chambers.

Ok, that's good and everything, however...

The big reason .223 is more accurate is due to the tighter chamber and limited leade. This statement would apply essentially only to commercial/military loaded ammunition.

However, I plan to primarily shoot reloads. What this would allow me to do is reload the shells so they fit tight into the chamber. Basically, fire the shell once, and neck-only resize from that point on. Case capacity should increase because the shell should fire-form to the 5.56 chamber.

So, given this, wouldn't that make 5.56 indistinguishable in accuracy vs .223?
Also, wouldn't the higher case capacity and higher pressure tolerances give me the capability to load higher velocities, in order to achieve longer distances?

And, if wanted, I could still shoot mil-spec ammo just fine.

I plan to get an E.R. Shaw 24" SS Varmint barrel in either .223 or 5.56mm and I would appreciate feedback on my 'theories'.

Thank You.

edit// If this is in the wrong section please feel free to move it.
Also, it occured to me that only neck sizing semi-automatic brass isn't going to be good, I guess I'd have to have special dies to reload specifically for the 5.56mm chamber.

Do some googling on the "WYLDE" chamber as well.

I am aware of the Wylde chamber, however I am limited to choose between 5.56 and .223 Rem.

Thank you for your response.

My Bolt action 222rem has been More Accurate than my 223rem bolt actions or AR15`s


Still both 5.56 and 223rem are Very Accurate

i have a question. does anyone feel it wasteful to use match ammo on a critter? but you almost have to right? other less consistent stuff can't hit the little things at range.

I wouldn't say that using match ammo is "wastefull" for hunting coyotes/predators because you need ammo that is going to go where you want it to go on such a small target.  I would use a hunting bullet that is made to expand though.

As the OP put in his post, he couldn't just neck size for a semi auto, without asking for problems with function.  There are no such thing as 5.56 dies either.  You will be stuck with some form of full length dies for reloading.  This is not a problem and you will be able to produce very accurate ammo, as good or better then anything factory.

How accurate are you looking for?  With a 223 or wilde chambering,you should be doing .75 to .50 groups at 100 yards with handloads, if you do your part.  MOA should be fine to take a coyote out to 600 yards or so, which is streching it a bit IMHO for taking a shot at such a small animal.

Quoted: The big reason .223 is more accurate is due to the tighter chamber and limited leade. This statement would apply essentially only to commercial/military loaded ammunition.   Not the only reason comm is better than mil- IMO its because of tighter QC and more uniform processing not the "tighter chamber" The tighter chamber will only lead to higher pressures and kabooms, constant neck pressure/ bullet setback form the lands is way more important However, I plan to primarily shoot reloads. What this would allow me to do is reload the shells so they fit tight into the chamber. Basically, fire the shell once, and neck-only resize from that point on. Case capacity should increase because the shell should fire-form to the 5.56 chamber. You generally can't just neck size SA rounds because the pressure in the round it during initial extraction, vs in a bolt gun all the pressure is gone and extraction is much easier. You at least need to FL size for S/A round or you will get stuck cases. realize you get the 556 pressures by having thicker brass. If you try to "stretch a 223 to fit a 556 chamber and get higher pressures then you will kaboom something So, given this, wouldn't that make 5.56 indistinguishable in accuracy vs .223? Also, wouldn't the higher case capacity and higher pressure tolerances give me the capability to load higher velocities, in order to achieve longer distances?   You do not need to be concerned with the velocities if you're varminting- bullet construction/accuracy would be a better area to concentrate on vs velocity alone, Velocity in and of itself doesn't control accuracy- you usually get the best accuracy before you get the fastest velocities. Velocity in the discussion of the 5.56 is paramount when dealing with the FMJ bullets/fragmentation, change the bullets and this "crutch" can be eliminated. And, if wanted, I could still shoot mil-spec ammo just fine. I plan to get an E.R. Shaw 24" SS Varmint barrel in either .223 or 5.56mm and I would appreciate feedback on my 'theories'. Thank You. edit// If this is in the wrong section please feel free to move it. Also, it occured to me that only neck sizing semi-automatic brass isn't going to be good, I guess I'd have to have special dies to reload specifically for the 5.56mm chamber.

I think you are a little misguided in your theroies, It looks like your confusing commercial ammo/223 chambers with reloads. Realize you reload to fit whatever chamber you have, 223 is probably easier with more die selection available.


if you want the best accuracy with comm ammo, get a 223 chamber, if you want to shoot both with great accuracy get a wylde chamber. Realize that nearly all decent 223/556 wylde guns will easily shoot sub moa. If you plan to reload, get the wylde chamber, some LC mill brass and use good reloading procedures and you will get match results- many have been doing this for years

It's all theory on paper until you pull the trigger.  

I had a .308 Remington 700VS that would literally shoot groups...get this in the .200-.225" range.  That's with a .308 caliber bullet, essentially one (barely) ragged hole.  The bullet it did this with?  110 grain Speer...a little dinky short bullet that had one hell of a jump before it engaged the leades.  According to calculations and internal ballistic theory, that should have been damned near impossible.  They even outshot 168 OTMs.  

The lesson I took away from it is that all the book leaning in the world don't mean shit until you burn some powder and boot leather.  YMMV.  

i guess i'm talking about the non reloader, especially for varmints. it'd be almost ridiculous to try to hit a ground squirel with federal american eagle or any other "mid grade" 5.56/223 round.

but reloading, yeah that definitely makes good sense.