.223 vs 5.56

[The Annoyed Man]

I know that, even though .308 Winchester and 7.62 NATO are very similar rounds, they are not exactly the same; the differences having to do with case capacity and head spacing; and although some rifles can chamber both, some rifles shouldn't.

My question is, are there similar distinctions between .223 Remington and 5.56 NATO, and if so, should this distinction be a safety/function issue in a Bushmaster Varminter rifle?

I've recently purchased one of these rifles, and it is my first foray into the .223 caliber. So far, I've only fired various commercial .223 loads through it, from cheap UMC ($99.95/box of 200), to expensive Federal Gold Match 69 gr SMK, and 2 or 3 offerings in between. If it is safe to do so, and if it won't excessively beat up my rifle (like being bad for the bore or something), I would probably buy mil-surp ammo just for plinking with. I just don't want to do it if it isn't good for the gun.

Any input would be appreciated.

Pic of the rifle attached:

 

[skinewmexico]

http://www.thegunzone.com/556v223.html

 

[George757]

Your Varminter has a 5.56 chamber, and can utilize .223 or 5.56. A gun that is chambered in .223 should not use 5.56 ammo, but that's not your case, so you're good-to-go with either ammunition.

 

[K3]

I would probably buy mil-surp ammo just for plinking with. I just don't want to do it if it isn't good for the gun.

I don't know if you roll your own, but if you want cheap AND very accurate plinking ammo for an AR, you ought to handload. 55gr FMJs or 62gr depending upon the twist rate.

 

[The Annoyed Man]

Thanks for the input everybody.

K3, I intend to start loading my own. I own enough firearms now that ammunition is becoming a burden. A friend of mine is going to bring his setup over to my house as he doesn't have room for it right now in his apartment. We're going to do up a bunch of .223 together.

 

[KBintheSLC]

A gun that is chambered in .223 should not use 5.56 ammo

+1

If it says 5.56, you can use either. If it says .223, you can only use .223

 

[Silvanus]

Interesting thread, I've wondered about this myself.

Is it the same for 7.62 NATO and .308?

7.62 for both, but in .308 only .308?

 

[Markbo]

What twist rate did you get your varminter in?

 

[TexasRifleman]

Is it the same for 7.62 NATO and .308?

Yes and no As usual huh?

7.62 and .308 are different according to the drawings, and the chambers themselves. But, no one is actually making brass that is to the 7.62 design, it's all .308 headspace spec. even the milsurp stuff that's out there. The brass is thicker with 7.62 usually, but not always. If you have NATO stamped brass then it's thicker for sure.

What this means is that headspace is very important. If you have a rifle that has a headspace out on the ragged edge of the 7.62 spec you might have a danger area firing .308 ammo since you are going to have thinner brass. You usually see this in machineguns like M60s, and Navy Garands for example, more exotic stuff for the most part.

If your headspace is in excess of 1.636 then you should only use 7.62 NATO spec type ammo.

Headspace in the range 1.631-1.632 is about right for both. If you keep your rifles headspace in the SAAMI ranges; 1.630 GO, 1.634 NO GO, 1.638 FIELD REJECT then you can shoot pretty much whatever you want though you will see most people recommending 1.636 as the max instead of 1.638, Kuhnhausen among them.

 

[rino451]

Quote:
Is it the same for 7.62 NATO and .308?
Yes and no As usual huh?

7.62 and .308 are different according to the drawings, and the chambers themselves. But, no one is actually making brass that is to the 7.62 design, it's all .308 headspace spec. even the milsurp stuff that's out there. The brass is thicker with 7.62 usually, but not always. If you have NATO stamped brass then it's thicker for sure.

What this means is that headspace is very important. If you have a rifle that has a headspace out on the ragged edge of the 7.62 spec you might have a danger area firing .308 ammo since you are going to have thinner brass. You usually see this in machineguns like M60s, and Navy Garands for example, more exotic stuff for the most part.

If your headspace is in excess of 1.636 then you should only use 7.62 NATO spec type ammo.

Headspace in the range 1.631-1.632 is about right for both. If you keep your rifles headspace in the SAAMI ranges; 1.630 GO, 1.634 NO GO, 1.638 FIELD REJECT then you can shoot pretty much whatever you want though you will see most people recommending 1.636 as the max instead of 1.638, Kuhnhausen among them.

Be careful, because .308 is a higher pressure round than 7.64 so while some might feel confortable shooting commercial .308 in modern NATO 7.62 chambered rifles (I'm sure that even this is ok), older guns and milsurps might not fare so well.

 

[manicmarauder]

for the 7.62x51 NATO vs. .308 Win.

This site explains it well, in the section entitled: ".308 Win vs. 7.62x51--The Straight Scoop"
http://www.6mmbr.com/308Win.html

Small excerpt follows:

Before we go much further, we want to address the oft-posed question "Are the .308 Winchester and 7.62x51 NATO one and the same?" The simple answer is no. There are differences in chamber specs and maximum pressures. The SAMMI/CIP maximum pressure for the .308 Win cartridge is 62,000 psi, while the 7.62x51 max is 50,000 psi. Also, the headspace is slightly different. The .308 Win "Go Gauge" is 1.630" vs. 1.635" for the 7.62x51. The .308's "No-Go" dimension is 1.634" vs. 1.6405" for a 7.62x51 "No Go" gauge. That said, it is normally fine to shoot quality 7.62x51 NATO ammo in a gun chambered for the .308 Winchester (though not all NATO ammo is identical). Clint McKee of Fulton Armory notes: "[N]obody makes 7.62mm (NATO) ammo that isn't to the .308 'headspace' dimension spec. So 7.62mm ammo fits nicely into .308 chambers, as a rule." You CAN encounter problems going the other way, however. A commercial .308 Win round can exceed the max rated pressure for the 7.62x51. So, you should avoid putting full-power .308 Win rounds into military surplus rifles that have been designed for 50,000 psi max.

Bold added by me

From Skinewmexico's link above:

The .223 Remington is rated for a maximum of 50,000 CUP while the 5.56mm is rated for 60,000 CUP. That extra 10,000 CUP is likely sufficient to cause a failure in a chamber that's only rated for the "sporting" .223 Remington.

So the .308/7.62 is the exact opposite of the .223/5.56

 

[TexasRifleman]

Be careful, because .308 is a higher pressure round than 7.64

Good point but remember it's not "is", it's "can be". Most .308 on the market falls right in the 762 pressure ranges according to lots of tests out there.

manicmarauder is more correct than both of us really, in his last sentence.

"You should avoid putting FULL POWER .308 into milsurp rifles" especially those that might be on the weaker side of things.

Seems like I remember the Ishapore riles being one where everyone cautions against using .308. I'm sure there are others.

Glad you guys brought that up.

 

[mpmarty]

Unfortunately the internet is a wealth of information. Most of it based on a total lack of knowledge and the rest on urban legend. Like the difference in chamber pressure for 308/7.62x51 or 223/5.56x45 the simple fact is there is little or no difference between the civilian and military rounds. You folks are comparing chamber dimensions with go no go gauges, again apples to oranges. As to chamber pressure it happens that 50,000 cup and 60,000 psi are the same pressures, just measured differently as in 6.5 and .264. Do you really believe that the reloading manuals which list SAAMI spec pressures for all cartridges make no distinction between the civilian and military cartridges due to ignorance of the "HUGE" differences between them?

 

[RockyMtnTactical]

http://ammo.ar15.com/

You should read this

 

[TexasRifleman]

As to chamber pressure it happens that 50,000 cup and 60,000 psi are the same pressures

Which has nothing to do with anything since the SAAMI standard pressure is 50,000 on the (CUP) scale or approx 62,000 psi, measured with a piezoelectric gauge, for the civilian .308 round. The NATO specification for 7.62x51mm is 50,000 psi so there is in fact a 12,000 psi difference between commercial .308's max pressure and NATO 7.62x51's max pressure.

308/7.62x51 or 223/5.56x45 the simple fact is there is little or no difference between the civilian and military rounds.

How in the world can you come to the conclusion that those are the same thing? At least as far as the 7.62 vs .308 comparison there is a HUGE difference.

You folks are comparing chamber dimensions with go no go gauges, again apples to oranges.

No we are not. There are 2 things to watch for in the .308/7.62x51 interchange.

1) Pressure. Commercial .308 has the potential to be loaded to a higher max pressure than 7.62x51, a 12,000 psi difference.

2) Headspace. Commercial .308 can have case rupture issues in 7.62x51 chambers with headspace dimensions exceeding the .308 spec while still remaining inside the 7.62x51 spec.

If you want to argue about it take it up with Jerry Kuhnhausen, that's all quoted directly from the guy that "wrote the book".

Do you really believe that the reloading manuals which list SAAMI spec pressures for all cartridges make no distinction between the civilian and military cartridges due to ignorance of the "HUGE" differences between them?

SAAMI does not publish or control the specs for NATO 7.62x51. What SAAMI does though is ignore half of the problem, since they only control half. On SAAMIs webpage they show unsafe combinations:

http://www.saami.org/Unsafe_Combinations.cfm

What you will see is that they only show combinations where the chamber is a SAAMI spec. So, they don't say that using 7.62x51 in a .308 chamber is unsafe since it's not, 7.62x51 has a lower pressure. Since 7.62x51 is not a SAMMI spec they don't mention the reverse, although we know that it is potentially a problem.

You will also note on this SAAMI webpage that they do not recommend using 5.56 in a chamber with a .223 spec, since it is potentially an unsafe combination.

Just because SAAMI doesn't mention it doesn't mean that it doesn't exist. Their only concern is with rounds that they publish specs for but they most certainly DO say not to use 5.56 in a .223 chamber.

 

[The Annoyed Man]

"What twist rate did you get your varminter in?" Markbo, it's 1:9.

 

[Markbo]

Everyone who shoots an AR or a .223/5.56 should read and save the Ammo Oracle that RockyMtnTactical posted. It is simply THE source for questions like this.

That being said AM, the 1:9 twist was tested to find it specifically beneficial for a 62gr round in the M16 platform. BUT I have had the greatest success in my 1:9 twist shooting 55gr bullets so just as K3 stated, I believe you should concentrate your reloading efforts in that range - 55 to 62gr.

Also of the manuals I have exactly ONE addresses the AR specifically. That is the Sierra book. By all means, get one. The best advice I ever got when I started handloading was to get 2 manuals. Read them cover to cover. Highlight areas you want to remember or you think are important. Then go back and read them again - do this before you ever TOUCH any reloading equipment.

I understand your buddy is going to be there, but you absolutely must have a good knowledge of what you are doing to understand why you must know this stuff, let alone learn it. A small mistake in the reloading room can lead to catastrophic results at the range. Other books I would recommend for the begginer is The ABC's of Reloading or the Lyman Reloading Manual. Both are very good books for the beginner.

 

[rc109a]

Rocky
Thanks for the link. That has answered just about any and all questions that I had about the 223/5.56 scenerio. A great read and should be made a sticky someplace. It should also be requried read BEFORE posting any more 223/5.56 questions.

 

[jkingrph]

I do not know how many rounds of 5.56 my 1971 vintage Rem 700 varmit special has consumed.

I bought it new when a young AF officer with the expressed intent of shooting a lot of military ammo.

Never a problem in 37 years!!!

 

[Rshooter]

Please do not recommend 5.56 and 308

Gentlemen please do not recommend 5.56 in a .233 or .308 in a 7.62 chamber to others. If you wish to do this that is fine. I have a low numbered Springfield that I shoot but I would never recommend this practice to another for safety reasons. My own indiscretions are mine.

 

[alsaqr]

Wake up and realize that SAAMI is run for ammunition manufacturers: Of course, they do not want you to use surplus military ammo. SAAMI is the same bunch who asked the BATFE to re-write regulations for ammo manufacture storage and distribution: Then the idiots whined when the ATF did exactly what they asked for.

Look at this Cheaper Than Dirt Ad:

http://www.cheaperthandirt.com/AMM223-46090-66.html

"We received a special lot of this military load ammunition in boxes that had a misprint, the box is marked M885 instead of M855, this simple box misprint is saving you a lot of money and making a very hard to get ammunition available in a very small quantity. Recommended for Law Enforcement or military use only.

Lake City .223 Ammo, is the best .223 Military ammo manufactured. This is the original US Military Lake City Arsenal M855 SS109 Penetrator ammo, 62 grain with steel tipped penatrating core for combat use, firing at 3,025 f.p.s., very scarce and limited supplies, 20 round boxes with US Markings. This is identical to the ammo being used right now in Iraq by U.S. Troops.

Probably the best .223 ammo for combat ever produced in the USA. So scarce in the commercial market we have not sold any in 15 years. Simply put, this is some of the best ammo on the surplus ammo market today at a great price."

 

[TexasRifleman]

Look at this Cheaper Than Dirt Ad:

What's your point? Cheaper than Dirt uses the terms 5.56 and .223 interchangeably? That's supposed to prove what?

There IS a difference between 5.56 and .223. For 99 percent of the shooters out there it doesn't, in reality, make a difference.

BUT if you own one of the rifles that fall into that 1 percent category you better know for a fact the differences between the 2 and what that might mean for you.

 

[alsaqr]

This gets hashed and re-hashed every couple of weeks on this forum. There are about one dozen different .223 and 5.56mm chambers.

This is the last iteration:

http://www.thehighroad.org/showthread.php?t=328489&highlight=.223/5.56mm

"What's your point? Cheaper than Dirt uses the terms 5.56 and .223 interchangeably? That's supposed to prove what?"

Do you think for even one minute that CTD would do this if it were dangerous to fire this ammo in a .223 chamber?

.223 rifles with tight chambers are out there, this is true. It is also true that most .223 OR 5.56mm ammo will not chamber in them without neck turning. Yes, Texas Rifleman, i also have one of them. They make up more like like .1 percent of the .223 rifles out there.


http://www.thehighroad.org/showthread.php?t=328489&highlight=.223/5.56mm

 

[TexasRifleman]

Do you think for even one minute that CTD would do this if it were dangerous to fire this ammo in a .223 chamber?

You mean outside of the fact that they put this on every order?

Come on, you think it's CTDs responsibility?

LIABILITY:
Not having control over the use of the
products in this catalog or on our website,
we assume no liability connected with
their use. Under no circumstances are
we or the manufacturer liable for any
losses, damage, or expenses of any kind
arising out of the use or inability to use
these products.

I guess I just don't understand the point in arguing it. There are differences between 5.56 and .223. They are not big and they don't impact most people. Why argue that? Is there some problem with just saying that and moving on?

 

[alsaqr]

"Why argue that? Is there some problem with just saying that and moving on?"

Sounds good to me.