223 vs 5.56 military

[mikedb]

I am a bit confused.  I thought 223 Rem could be fired in a rifle chambered for the 5.56 military round (AR15 for instance). But not the other way around.  I have been seeing ammo listed as 223 or 5.56.  So I assume this is just 223? Bottom line is I should not fire 5.56 NATO or other 5.56 ammo in my Savage 223Rem correct?

[beemanbeme]

No, that is not correct.  There has been tons of milsup 5.56 ammo shot thru every sort of .223 rifle. 
When they realized that the 5.56 was a pretty cheezy round to be sending troops into combat with, they tried to juice it up with a heavier bullet.  And ran into a stability problem.  So they changed the twist rate so it would stabilize the heavier bullet.  If you have a standard twist in your Savage --12 or 14-- you can shoot the milsup with 55gr bullets.  If your Savage has a twist of 7 or 9, you will need the heavier bullets and you will gain better long range performance. 
I don't know what sort of accuracy you would get from a fast twist rifle and say a 50 or 55gr bullet.

[Blackhawk44]

Other than the twist rate, the difference was in the chamber throating specs.  The original .223 chamber had a very short throat (almost none) and the mil spec chamber had a longer tapered lead.  Mil spec loads in the .223 chamber throat would jam into the rifling and raise pressures.  A good many manufacturers have gone to the military spec chamber due to the proliferation of surplus ammo and to save confusion.  Many guns that have done so are marked .223/5.56mm.  I do no know about Savage. 

[mikedb]

Other than the twist rate, the difference was in the chamber throating specs.  The original .223 chamber had a very short throat (almost none) and the mil spec chamber had a longer tapered lead.  Mil spec loads in the .223 chamber throat would jam into the rifling and raise pressures.  A good many manufacturers have gone to the military spec chamber due to the proliferation of surplus ammo and to save confusion.  Many guns that have done so are marked .223/5.56mm.  I do no know about Savage. 

Yes, that is what I remember.  The Savage is not marked that way so I will only use 223 unless I have the chamber checked.

[Gregory]

http://www.winchester.com/lawenforcement/news/newsview.aspx?storyid=11

News and Press Releases
.223 Rem VS 5.56mm
 
Paul Nowak
5/4/2001
.223 Rem VS 5.56mm

There are a lot of questions about these two cartridges. Many people think they are identical - merely different designations for commercial and military. The truth is that, although somewhat similar, they are not the same and you should know the differences before buying either cartridge.

    * The cartridge casings for both calibers have basically the same length and exterior dimensions.
    * The 5.56 round, loaded to Military Specification, typically has higher velocity and chamber pressure than the .223 Rem.
    * The 5.56 cartridge case may have thicker walls, and a thicker head, for extra strength. This better contains the higher chamber pressure. However, a thicker case reduces powder capacity, which is of concern to the reloader.
    * The 5.56mm and .223 Rem chambers are nearly identical. The difference is in the "Leade". Leade is defined as the portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. It is also more commonly known as the throat. Leade in a .223 Rem chamber is usually .085". In a 5.56mm chamber the leade is typically .162", or almost twice as much as in the 223 Rem chamber.
    * You can fire .223 Rem cartridges in 5.56mm chambers with this longer leade, but you will generally have a slight loss in accuracy and velocity over firing the .223 round in the chamber with the shorter leade it was designed for.
    * Problems may occur when firing the higher-pressure 5.56mm cartridge in a .223 chamber with its much shorter leade. It is generally known that shortening the leade can dramatically increase chamber pressure. In some cases, this higher pressure could result in primer pocket gas leaks, blown cartridge case heads and gun functioning issues.
    * The 5.56mm military cartridge fired in a .223 Rem chamber is considered by SAAMI (Small Arm and Ammunition Manufacturers Institute) to be an unsafe ammunition combination.

[mikedb]

I will take this to the local Gander Mt.  They are the ones that got me rethinking what I knew was right.  They had 5.56 ammo on a shelf and under it was marked by them as 223.  At least they have deep pockets if a gun goes.  Thanks I needed something like the linked article to make them realize I was correct.

[beemanbeme]

I wisht someone would authenticate a rifle blowing up from the use of milsup ammo in a .223.  Maybe even post some pictures.   

[The Sodbuster]

Gregory posted the following news from Winchester:

The 5.56 cartridge case may have thicker walls, and a thicker head, for extra strength. This better contains the higher chamber pressure. However, a thicker case reduces powder capacity, which is of concern to the reloader.

I have .223 Rem military brass and civilian brass.  I've weighed different brands of .223 brass and found Remington brass to be the heaviest, and to have the smallest case capacity.  All brass was sized, cleaned, and trimmed to same length.  Given identical outside dimensions, the only explanation for R-P brass to be heavier is it has to be thicker somewhere.  This surprised me as I had always heard military brass was thicker.  I haven't found this to be the case (pun intended).

[beemanbeme]

GI brass of the '06 and .308 era is thicker.  While I haven't done any extensive weighing, I understand that 5.56 brass is the same as the house brand .223 brass.

[Gregory]

Gregory posted the following news from Winchester:

The 5.56 cartridge case may have thicker walls, and a thicker head, for extra strength. This better contains the higher chamber pressure. However, a thicker case reduces powder capacity, which is of concern to the reloader.

I have .223 Rem military brass and civilian brass.  I've weighed different brands of .223 brass and found Remington brass to be the heaviest, and to have the smallest case capacity.  All brass was sized, cleaned, and trimmed to same length.  Given identical outside dimensions, the only explanation for R-P brass to be heavier is it has to be thicker somewhere.  This surprised me as I had always heard military brass was thicker.  I haven't found this to be the case (pun intended).

Yes, I quoted a link that said mil bras MAY be thicker.  The link more importantly said:

http://www.winchester.com/lawenforcement/news/newsview.aspx?storyid=11

News and Press Releases
.223 Rem VS 5.56mm
 
Paul Nowak
5/4/2001
.223 Rem VS 5.56mm

    * The 5.56mm and .223 Rem chambers are nearly identical. The difference is in the "Leade". Leade is defined as the portion of the barrel directly in front of the chamber where the rifling has been conically removed to allow room for the seated bullet. It is also more commonly known as the throat. Leade in a .223 Rem chamber is usually .085". In a 5.56mm chamber the leade is typically .162", or almost twice as much as in the 223 Rem chamber.
    * You can fire .223 Rem cartridges in 5.56mm chambers with this longer leade, but you will generally have a slight loss in accuracy and velocity over firing the .223 round in the chamber with the shorter leade it was designed for.
    * Problems may occur when firing the higher-pressure 5.56mm cartridge in a .223 chamber with its much shorter leade. It is generally known that shortening the leade can dramatically increase chamber pressure. In some cases, this higher pressure could result in primer pocket gas leaks, blown cartridge case heads and gun functioning issues.
    * The 5.56mm military cartridge fired in a .223 Rem chamber is considered by SAAMI (Small Arm and Ammunition Manufacturers Institute) to be an unsafe ammunition combination.

[alsaqr]

This is something that i never worried about.  Fired tens of thousands of rounds of 5.56mm in my .223 rifles over the past 40 years.    The most accurate is some US Army headstamp TW 67 stuff.  This will easily shoot .75 inch 100 yard groups in my rifles.  The South African 5.56mm is also very accurate in my rifles.   The sorriest stuff i ever bought was some Sellier and Bellot.  It was not accurate by anyone's standards.   

[shotgun31]

I have a 1980's era R700 that started life as a 222.  I had it rechambered to .223 and I told the gunsmith that I wanted to shoot military rounds in it.  He created what he called "freebore" and I believe that's what Weatherby does with their .300 for performance while keeping pressure down.

The only problem with this rifle is the 14X1 twist.  In winter at 100 yds the bullets are full profile on the target and I can't hit a 10X10 foot target frame at 200.  Summertime the military rounds are deadly on PD's out to 150 or so--then they seem to just slip through the critter.

Best load includes a 50 Hornady spire, 4198 and a powder charge that I won't mention.  The freebore allows a bit more than the loading manual--no pressure signs.  It's a 1" plus at 100 yard rifle, but has killed a long, long way out.

Point is, I've fired thousands of rounds through a 223, but it's a gunsmiths chambering of a 223.  Maybe someone with more chambering experience could shed some light on this set-up.
 

[Larry Gibson]

I started rechambering .222s in 1970 with a .223 chambering reamer (still have it) and fired thousands of M193 through several of them and other commercial .223s. I've also fired thousands of M193 and M855 through a Savage Competition rifle with a 1-9" twist. The barrel was set back and it has a tight chamber and minimal leade. No problems there at all. Never had a hint of pressure sign or erratic results over the chronograph. Until I see actual test results I will continue to believe this to be a myth. Ranks right up there with the 7.62 vs .308 Winchester myth.

Larry Gibson

[alsaqr]

"I started rechambering .22s in 1970 with a .223 chambering reamer (still have it) and fired thousands of M193 through several of them and other commercial .223s. I've also fired thousands of M193 and M855 through a Savage Competition rifle with a 1-9" twist. The barrel was set back and it has a tight chamber and minimal leade. No problems there at all. Never had a hint of pressure sign or erratic results over the chronograph. Until I see actual test results I will continue to believe this to be a myth. Ranks right up there with the 7.62 vs .308 Winchester myth."

Never had any problem with my guns either.  First rifle i had re-chambered for .223 is a beautiful Sako in .222.   Greatly decreased the value but it sure shoots good.  Here is some info on the effectiveness M193 and other military rounds.  The M193 bullet zaps coyotes as if struck by lightning out to about 150-175 yards.  Does not matter much where you hit them.  After about 175 yards it is not nearly as effective. 





http://home.snafu.de/l.moeller/Zielwirkung/military_bullet_wound_patterns.html

[Larry Gibson]

 The M193 bullet zaps coyotes as if struck by lightning out to about 150-175 yards.  Does not matter much where you hit them.  After about 175 yards it is not nearly as effective. 

http://home.snafu.de/l.moeller/Zielwirkung/military_bullet_wound_patterns.html

I found out the same thing with M193 out of 1-14" twist barrels. The bullets tumble quickly in critters, even small 5-8 lb rockchucks. They weren't quite so effective on broadside jack rabbits though.  We noticed a difference between the impact effectiveness of the XM16 (the original green stocked ones) and the later blackstocked M16s we had in '65 in RVN. We didn't know about the change in twist between the two. In the past, as a demonstration to others, I've laid numerous 10-12 lb rockchucks (already dead bu not blown up) side by side and shot them with a M788 (rechambered from .222) with 1-14" twist and a M700V with 1-12" twist with M193 ammo at 50-100 yards. The M788 would flip them off the rock and they'd have a good size exit wound. The M700V's M193 bullet would zip on through them and the body would hardly move. Imust mention that accuracy of the M193 fell off dramatically wit the 1-14" twists when the temperature dropped below freezing. This was the reason the twist was changed to 1-12" when the Air Force found accuracy problems in Alaska during the winter.

Larry Gibson


Larry Gibson