Best chamber for handloading 223 or 556?

[tbrice23]

I've never owned a AR15 and have a couple of choices for barrels,
One is 1:9 twist 556,
The other is 1:8 twist 223.

I'm torn because the 556 is supposed to have longer throat but has a slower twist. The other consideration is mag length.
What to do??

 

[Darkker]

If you are handloading, the chamber, or more correctly the throat; really isn't important. The twist is what you need to think about.
What you want to do with it, will answer this. Light varmint bullets many times can't survive the 8-twist. Dogtown's won't survive the 9-twist at times. But the 9 likely won't stabilize the 75gr V-max.

 

[tbrice23]

I plan on anything from 69gr Matchkings to 75 gr VLD.

 

[MudRunner2005]

I plan on anything from 69gr Matchkings to 75 gr VLD.

5.56x45 NATO chamber, 1:7 twist. Make sure the barrel is stamped 5.56.

 

[venatic]

I would go with the 8 twist barrel myself and take the 223 chamber over the 5.56 all day long.

 

[Kansaswoodguy]

If you want to fling lead all over the place go with the NATO chamber if your more into precision shooting get the 223 Rem. The twist rates are 1-9 which may or may not stabilize the 75's most likely it will but there's a chance it won't. The 1-8 twist will stabilize the 75's no problem. There is also at least in the AR world what's called a 223 Wylde chamber it's basically a NATO chamber with a 223 Rem neck. The drawback to a 223 Rem is your not supposed to use NATO ammo do to the higher pressures. The 223 Wylde solves this. In order of accuracy from the best to worst in theory.

223 Rem
223 Wylde
5.56 NATO

I have 4 223 Rem chambered guns, 2 223 Wylde chambered guns and 2 5.56 NATO's for precision work you want nothing to do with a NATO chamber I'd take one of the others with no real preference there both good.

 

[Kansaswoodguy]

Brice

If this is going to be for an AR you won't be able to run the 75 VLD's mag length. I use the 75gr Hornady BTHP match bullets or the 77gr Sierra's they both can be loaded to mag length.

 

[MudRunner2005]

If you want to fling lead all over the place go with the NATO chamber if your more into precision shooting get the 223 Rem. The twist rates are 1-9 which may or may not stabilize the 75's most likely it will but there's a chance it won't. The 1-8 twist will stabilize the 75's no problem. There is also at least in the AR world what's called a 223 Wylde chamber it's basically a NATO chamber with a 223 Rem neck. The drawback to a 223 Rem is your not supposed to use NATO ammo do to the higher pressures. The 223 Wylde solves this. In order of accuracy from the best to worst in theory.

223 Rem
223 Wylde
5.56 NATO

I have 4 223 Rem chambered guns, 2 223 Wylde chambered guns and 2 5.56 NATO's for precision work you want nothing to do with a NATO chamber I'd take one of the others with no real preference there both good.

I have 5.56 NATO chamebered barrels that shoot consistently 1/2-1 MOA...And 1-1.5 MOA with cheap steel-cased east-block stuff. I would hardly call that "slinging lead all over the place"... Barrel quality, chamber quality, and rifle build quality has more to do with accuracy than what's stamped on it, or the throat length.

 

[bigedp51]

Both the .223 and 5.56 are loaded to the same chamber pressure of 55,000 psi, the problem is the 5.56 throat is twice as long as the .223. Meaning when you shoot M855 military ammo in a .223 with a shorter throat the chamber pressure will be approximately 60,000 psi.

I have two AR15 rifles a A2 HBAR with a 1 in 9 twist and a carbine with a 1 in 7 twist. And to add more confusion I have a Savage .223 that has a longer throat than either AR15 with a 1 in 9 twist. (.0566)

If you are buying a AR15 go with the longer throated 5.56 chamber and you will be able to shoot any .223/5.56 ammunition and any of the longer heavier bullets.

The main difference with a military 5.56 chamber is it is approximately .002 larger in diameter with slightly longer headspace settings. This hurts nothing because the resized case should be at least .003 to .005 smaller in diameter for reliable extraction.

NOTE, Lake City 5.56 cases and civilian contract 5.56 for the military has the hardest brass in the base of the case. And the flash hole web is thicker meaning the military cases primer pockets last longer and do not stretch out as fast as softer .223 cases. I buy once fired Lake City cases from Brass Bombers .223/5.56 Cleaned, Deprimed & Swaged Lake City Brass 200 Piece Sample $28.00
.223/5.56 Cleaned, Deprimed & Swaged Lake City Brass 500 Pieces $59.00

It is the .223 rifles with a 1 in 12 or 1 in 14 twist that cause the pressure problems. And my .223 throat is long enough to fit the cartridge and the company lawyer in.

HOLLIGER ON .223/5.56 CHAMBERS
NJ HiPower - Cartridge Tech Specs

 

[FEENIX]

If you want to fling lead all over the place go with the NATO chamber if your more into precision shooting get the 223 Rem. The twist rates are 1-9 which may or may not stabilize the 75's most likely it will but there's a chance it won't. The 1-8 twist will stabilize the 75's no problem. There is also at least in the AR world what's called a 223 Wylde chamber it's basically a NATO chamber with a 223 Rem neck. The drawback to a 223 Rem is your not supposed to use NATO ammo do to the higher pressures. The 223 Wylde solves this. In order of accuracy from the best to worst in theory.

223 Rem
223 Wylde
5.56 NATO

I have 4 223 Rem chambered guns, 2 223 Wylde chambered guns and 2 5.56 NATO's for precision work you want nothing to do with a NATO chamber I'd take one of the others with no real preference there both good.

Another vote for the .223 Wylde and in 1:7".

 

[243winxb]

Factory ammo 5.56 vs 223

SAAMI - Not to shoot Factory 5.56 Military/Nato ammo in a 223 chamber. High pressure may result.

TECHNICAL DATA SHEET
UNSAFE FIREARM-AMMUNITION COMBINATIONS http://www.saami.org/specifications_and_information/publications/download/SAAMI_ITEM_211-Unsafe_Arms_and_Ammunition_Combinations.pdf

 

[tbrice23]

If you want to fling lead all over the place go with the NATO chamber

for precision work you want nothing to do with a NATO chamber I'd take one of the others with no real preference there both good.

This 556 NATO looks good to me, virgin brass and 16 power scope at 200 yards.

 

[bigedp51]

I've never owned a AR15 and have a couple of choices for barrels,
One is 1:9 twist 556,
The other is 1:8 twist 223.

I'm torn because the 556 is supposed to have longer throat but has a slower twist. The other consideration is mag length.
What to do??

Your dealing with a AR15 semi-auto rifle with a "longer" throat that will fire any .223/5.56 ammunition because of its longer throat. The throat was lengthened after M855 ammunition was adopted and before this the M-16 rifle had a shorter throat.

"BUT" as I stated before my Savage .223 bolt action with a 26 inch heavy barrel has a "LONGER" throat than either of my AR15 rifles. And many of the newer .223 rifles have room in the chamber for any type cartridge and also fit the company lawyer in. (they have longer throats)

My target AR15 A2 HBAR has a 1 in 9 twist, my AR15 carbine has a 1 in 7 twist and my Savage .223 bolt action has a 1 in 9 twist. (AR15 throat .0500 Savage .223 throat .0566)

AR15 rifles are over gassed and depending on the type gas system can chew up your case rims. So when I built my carbine I bought a mid-length gas system and not pound the rifle and brass to death.

The longer throat and AR15 twist rates will allow you to use longer heavier bullets. The shorter throated .223 rifles with 1 in 12 and 1 in 14 rifles were designed for lighter bullets.

If you want to shoot bug hole groups get a bolt action with a tighter chamber. The AR15 chamber is .002 larger in diameter and your resized cases should be .003 to .005 smaller in diameter than the fired case for reliable functioning in a semi-auto.

You need to decide on a rifle length or carbine length barrel. You need to decide on what bullet weights you want to shoot.

I'm a cheap bastard and I buy once fired Lake City brass for my AR15 rifles and my .223 bolt action.

Bottom line, get the standard longer AR15 chamber and just wait for the zombies to get closer and shoot them in the head. If you want to shoot the zombies in the head at longer ranges then get a bolt action with a tighter chamber. BUT you may have to run after firing 5 rounds and loose all your fired Lapua brass.

 

[tbrice23]

Bigedp51,
I bought the 556 NOTO 9 twist pictured in the post above, that 10 shot group I shot today in a 12 mph full value wind at 200 yards.
This bbl only has 30 rounds shot and is barely broken in but I believe I would have drilled a few zombie heads out to 450 or so with the load pictured.
This thing is so easy to handload for, even though I am jumping these 69gr SMK over a tenth of an inch to the rifling to fit as mag length. I might just re-shoot this load for validation and call it good.