How much accuracy is lost in using 223 Remington cartridges in a  5.56 chamber versus using the 223 remington in a 223 remington chamber?? Building a varmint gun and still undecided....
Been to the oracle but surely someone can give me firsthand answers.

Doubt you shoot well enough to determine the difference, no offense intended, it's just that only someone with a High Master card would be qualified enough to actually tell, (and even they might have trouble).

A custom reloaded round for YOUR rifle will probably shoot well no matter what chamber is in it, as long as your shooting Sierra bullets. Might make some difference (probably marginal) shooting Hornady bullets which unlike the Sierras, don't like to jump, but prefer to be close to the lands.

FWIW, as most varmint hunters roll their own rounds, most myself included, have SAAMI spec 223 chambers in their long range AR15s. (this fits the SAAMI spec 223 dies, which are used in reloading)

Mike

While we are on the topic, whats the story with 80 and 90 grain .223. Can I take a 90 grain round, hand load it into my 5.56mm chamber, lock the bolt into battery and shoot it safely? or will this need a special throat/chamber?

There are plenty HP shooters shooting the 90s, (most probably have Wylde or long throated chambers) I personally have only tested the 80s in my rifle and while "long-loaded" (for single fire) they shoot very well, I disliked the single loading aspect and prefer mag length 77 SMKs, which in my rifle don't give up too much, YMMV w/ your rifle.

Sorry, btt for 90grn. shooters, (perhaps the Competition forum would be a better spot for this second question as they have mucho mas experience more than I with them)

Mike

80 or 90 grainers huh?  That question cannot be adequately answered with the information provided...

Safety will be determined by a couple of issues. There are two that readily come to mind:  powder charge and cartridge length.

If your magical mystical super duper 90 grain load has an appropriate powder charge AND if the bullet is seated properly you will be good to go.  However, if you are trying to get 3200 FPS out of a 16" AR with 90 grain bullets in little itty bitty 5.56 cases, your powder charge is NOT SAFE.  And if your bullet is seated waaayyyyy out there and in tight up against the throat in the chamber, all bets are off...

A lot of shooters cut away the front of a magazine to gain some additional overal cartridge length and to place the bullet a bit closer to the lands.  Or they single load for the 600 yard line.  Better be careful in both cases.

Can you load up some 80 or 90 grainers and be good to go?  No damn way.  You gotta do your homework, just like your should be doing with ANY homerolled ammo........  Even if it is safe, it doesn't mean your 1/12" or 1/9" barrel will shoot em worht a damn,

Frozenny

I'm pretty sure you need FASTER THAN 1:7 to shoot 90's... something like 1:6.5

I played around with using 80 gr SMK's in my M4 (5.56 chamber, 1 in 7 twist barrel)
They shot well, but I had to single load them.  I switched back to the 77 gr SMKs and haven't looked back.  They shoot as well as the 80's for the distances I plan on using my M4 at, plus they are easier to reload. . .

(I was using the 80's in LC 00 brass, on top of Winchester primers and 25.4 gr of Varget, set 0.0002 inches off the rifling, and the 77's are loaded the same way, but they are mag length)

Quoted: 80 or 90 grainers huh?  That question cannot be adequately answered with the information provided... Safety will be determined by a couple of issues. There are two that readily come to mind:  powder charge and cartridge length. If your magical mystical super duper 90 grain load has an appropriate powder charge AND if the bullet is seated properly you will be good to go.  However, if you are trying to get 3200 FPS out of a 16" AR with 90 grain bullets in little itty bitty 5.56 cases, your powder charge is NOT SAFE.  And if your bullet is seated waaayyyyy out there and in tight up against the throat in the chamber, all bets are off... A lot of shooters cut away the front of a magazine to gain some additional overal cartridge length and to place the bullet a bit closer to the lands.  Or they single load for the 600 yard line.  Better be careful in both cases. Can you load up some 80 or 90 grainers and be good to go?  No damn way.  You gotta do your homework, just like your should be doing with ANY homerolled ammo........  Even if it is safe, it doesn't mean your 1/12" or 1/9" barrel will shoot em worht a damn, Frozenny

By hand load I meant manually loading the cartridge into the chamber, not reloading the bullet and powder and bullet into the cartridge case. I don't reload any more, I just don't have the time.

Maybe I'll just stick with 77 grain in my 5.56 1/7 and see how it works. I haven't shot anything heavier than 62gr yet, just looking for a little more range.

Ok, back to discussion at hand please!! I will never shoot anything over 77-80 grain and never single loaded in the rifle I am building!! I guess , to be more specific, what is the difference in Millitary 55 grain stuf and 223 Remington stuff. I know the 5.56 chamber is deeper "throated" so to speak to make use of longer heavier loads. But is there any physical difference in the 2 brands of 55 grain stuff other than maybe powder charge?? The oracle goes over the chamber diff but not much is said about cartridge diffs and why?

Toxic,

I don't know how the conversation turned to heavy bullets but (as I'm sure you know) for varmint hunting you want to go with fast, light, and "explosive" bullets such as V-max.

It seems most ARs are pretty accurate... my 20" with a run of the mill Shaw barrel shoots sub MOA groups (just slightly under an inch at 100 yds) and that has a 5.56 chamber.... and I bet alot of people can make the same claim.

Yes, as a rule of thumb you want to reduce the amount of freebore and keep the bullet close to the rifling... but some pretty accurate guns (such as Weatherby) use very LONG throats and still print good groups.

Scot

Quoted: I'm pretty sure you need FASTER THAN 1:7 to shoot 90's... something like 1:6.5

The only time I ever heard of a twist faster than 1/7 was when Glen Zedicker pushed a 90 past 3000 fps from a .30 Remington based wildcat.

Combat jack.  Twists faster than 1.7 are pretty common in LARGE caliber factory rifles. Marlin makes a guide gun in 1.2 . Think 408 ruger, 38/55, Large caliber bullets that need to be spun up fast!

What is the largest SAAMI 223 load available?? Is the Hornady 77 grain match bullets  SAAMI or 5.56?

Back on topic huh?  Okay...

There are differences between the .223 and 5.56 chambers.  These have been discussed at length elsewhere.  You wish to build a varmit rifle, so it is logical to assume you are likley going to be using some variation of .223 load (instead of 5.56).  In addition, I also assume you want to wring the most accuracy possible out of a varmint rifle.  The .223 chamber is the only way to go...

Accuracy differences between a 5.56 and .223 chamber are insignificant in  many situations( ie your M4 carbine plinker/defensive gun).  However, in a varminter application, these marginal differences are important.  I personally find that a 1/2 moa rifle is a far more viable varminter than say a 1 moa gun.  The .223 chamber will permit maximum accuracy.

I have seen all kinds of loading practices intended to help overcome the accuracy shortcomings of the 5.56 chamber.  The 5.56 is designed for safety, for generous tolerances on military ammunition, and for reliability under difficult conditions.   Most of these guns can shoot 1.5 to 1 moa.  This is good, but it it not varminter accuracy in my book.  

The .223 chamber is similar but intended primarily for increased accuracy.  It is designed for tighter tolerance commercial ammo, and places an emphasis on accuracy over utter reliability.  A good varminter 223 barrel with appropriate ammo should group 1/2 moa or damned close to it.

If you want a defensive rifle consider a 5.56 with a chromed bore.  If you want a varminter consider a .223 chamber in a stainless barrel or a non-chromed chrome-moly barrel.   This is even more important if you are not going to handload, as you will have less flexibility with regard to setting bullet seating depth.  If this is to be a true varminter, I'd suggest you consider a 1/12" twist...  The better varmint bullets for the .223 are in the 50-55 grain range, and 1/7" serve no purpose in this case.

There will of course be the odd exception to the rule.  However, as good as the 5.56 chamber is, it will not be as consistently accurate as the typical .223 chamber.  The 5.56 design criteria values safety and reliability under all conditions over sterling accuracy.  Truly successful varmint rifles value accuracy.  A consistent 1/2 moa rifle may not be an appropriate defensive rifle but it sure is a whole lotta fun ....  When your rifle is dialed in and you KNOW it is minute of eyeball out to 200 yards and still a viable crow rifle from 200-300 you are going to have a considerable amount of fun...

Frozenny

Can I stick my toe back in the pond TWEEK?? What did not come through was my edit to the statement I made to combat Jack.  My server at work started blocking AR15.com heck

Since I am new to AR's I have been reading as much info and trying to cipher the bull$hit in between.  From what I can find their are 4 different barrell chamberings for the AR.

5.56  nato spec  Shoots darn near everything

223 Remington SAAMI spec, tighter tolerance in chamber , shorter throat.

Wylde   an RRA offering.... Made by ?? Wilson?? A "halfway" between 223 Sami and 5.56

5.56 National Match....  Krieger I know makes these, tighter chamber than Nato but has deeper throat for the longer loaded match bullets. For match ammo only.


Are they more????
Anyway this gun is for varmint so I had Krieger chamber one in 223 Remington, Can't wait till it gets here. Although this means I will have to build another AR in 5.56 for "other" uses.