Is your chamber .223 or 5.56 and are you so sure?

[barnbwt]

So if the free bore of 223 is so short, how can it safely handle 77gr loads without engaging the lands, while a much shorter 5.56 will somehow cram against the rifling? Am I missing something?

Also, gun chambers and bolts have extremely high safety factors for good reason--blown/loose primers would be the only real effect of an extra 10ksi

I wonder how many of these incidents are caused by bullet setback or miscut chambers? 223 and 5.56 are just names attributes to the reamers sold by manufacturers. That they have different names and slightly different dimensions does not necessarily make them incompatible (case in point Blackout v Whisper, Tokarev v Mauser)

I have heard that NATO calibers have thick cases, for added safety in blowback guns, but that is only an issue for hand loaders who have to account for the reduced case volume. The case still doesn't carry a significant amount of pressure.

TCB

[Art Eatman]

barnbwt, re the 77-grain, doesn't it depend on the overall length of the cartridge? Touching the lands is okay, if the powder charge is appropriate for the condition.

Chambers and reamers have tolerances, measured in plus-or-minus thousandths of an inch. That's why many handloaders measure the dimensions on their fired brass, to determine if they have a minimum or maximum chambering.

Seems to me that regardless of what most folks have "gotten away with", if a person has a .223 rifle and wants lesser-cost 5.56 as the primary usage, reaming the leade to 5.56 spec would be a preferred action.

[reynolds357]

I interchanged the two for so long (before I knew that they are technically not the same thing) that by the time I figured out what I had been doing, I figured if I were going to mess anything up I would have done it a long time ago. Now? I pay no attention whatsoever to 5.56 or .223.

[thallub]

Show me the kabooms, please!!!

Been firing 5.56mm US military ammunition in .223 chambers since at least 1968 when i re-chambered a very nice Sako .222 to .223. Did it because i was in Army EOD and got oodles of free 5.56 ammo. All my .223 guns have had a steady diet of 5.56mm. That Sako has gone through at least four barrels since it was re-chambered.

Most factory guns are not chambered by gunsmiths. There is a race to bottom when it comes to labor. The chamber you get depends on the skill and attitude of the worker wielding the reamer. That reamer may meet some spec or the other, assuming it has not been re-ground.

NEF was famous for its inconsistent .223 chambers. Some chambers were huge, sloppy and even out of round; while others were tight. NEF re-ground their reamers.

Yep, one should not fire 5.56mm military ammo in tight match chambers; it probably will not fit anyway.

Strange that SAAMI waited until zillions of rounds of 5.56mm ammo hit the US market before posting their dire warning.

5.56 vs .223 – What You Know May Be Wrong

http://www.luckygunner.com/labs/5-56-vs-223/

[thallub]

I have heard that NATO calibers have thick cases, for added safety in blowback guns, but that is only an issue for hand loaders who have to account for the reduced case volume

Yep, that's a persistent SAAMI myth. Since 1968 i've weighed the cases for my accuracy loads. US made 5.56mm military cases are not thicker than commercial .223 cases.


Go to brass weights:

http://ar15barrels.com/tech.shtml

[kraigwy]

The article's logic seems to be stating that the bullet hitting the lands is what causes the peak pressure that is damaging, so that would be an issue involving bullet weight and overall length. But mil-spec ammo is ~60gr, and 223 is the more variable caliber coming in over 70gr in certain loadings . If anything, shooting 223 in a 5.56 chamber would cause this problem, not the other way around. Also, the powder differences causing a longer sustained pressure wave will not stress a chamber additionally--the peak load is still the same, it's duration is not a factor in the stress formulae. However, a slower powder's long pressure curve can cause a kaboom if the chamber is allowed to unlock too early, which is easier to do with a slower powder.

Also worth mentioning is that the article is actually a sales pitch for Murray's chamber reaming services --just something to keep in mind. I'm not a professional ballistician or acclaimed gunwriter/gunsmith, but I have an engineering degree and enough sense to know when scientific explanations don't jive with their arguments. Really it sounds like Murray's argument is that black rifle owners should take the time to determine how their chamber was cut, and whether it will function safely with their ammo choices, and why.

This ^^^^^^^

That's what throws me. It wasn't until the internet that I found out that civilian 223s had a throat too short to take 5.56.

The 77 gr SMK is a bad example, it still is loaded to fit the magazine, which means its not getting to the lands.

But then High Power shooters want a longer bullet to reach 600 & 1000 yards. They are single loaded so there is no need to stuff them in a magazine. So they load them long. Sierra says the OAL of their 80 SMK should be 2.550, much longer then any military round out there. Then there is the 90 gr Bergers.

I've seen more then one HP shooter start the bullet in the case enough to hold it, then do the final seating when they load the round in the chamber. They hit the Lands. And they aren't loaded light.

John at WOA recommended to me for his White Oak Uppers, 24.4 gr of R-15 for both the 77 & 80 gr SMKs.

Take your Hornady Case Seating gage, run it in your rifles, and see how long you can seat the bullets before they touch the lands. Compare that with the length of 5.56 rounds.

[4runnerman]

Would I do it--No. Even when times were tight,I never was even close to being short on 223 cases,primers ,bullets or powder, (still not ). That being said,my long range load in 223 is a 75 gn Hornady,seated,,well,,when I close the bolt. I do not skimp on powder either. I would venture to say much higher pressure than Nato rounds. This summer I had the oppertunity to shoot with 4 National Guard people, that shoot Matches for the Guard. In my time I spent shooting and talking to them I was informed all 4 had been shooting Nato rounds in their 223 for the last 7 years. Never a issue nor a mishap. Heck my standard load I shoot in 60 gn Hornady is probebly higher presssure than Nato rounds. This subject comes up every 4 or so months and will never be resolved. There are two thoughts on this subject
1- never ever
2- Makes no difference

Choose your side and let it ride. I don't simply because I dont need to.

Also If it was that bad,you would have heard of a issue already, I for one have never heard of one yet in 30 plus years of shooting.

[ripnbst]

5.56 can shoot .223 but .223 can't shoot 5.56. All you need to know out of all this information. KISS.

[Budda]

Send me all the 5.56 I will get rid of it for you. It is evil and will get your daughter pregnant and wipe your hard drive clean. It will also leave your fridge open and the toilet seat up. So do yourself a favor and send it all to me.

[thallub]

Yep, .223 and 5.56mm cartridge cases have the same dimensions. Yep, folks load cartridges with really long heavy bullets in .223 chambers.

The 5.56mm chamber was designed for full auto weapons of war. Military full auto weapons are designed to fire under all kinds of adverse conditions with ammo that may be dirty: Hence the longer leade.

In one article Sweeney claimed the leade of the 5.56mm chamber was longer to accomodate the 5.56mm tracer bullet which is longer. Well, Sweeney obviously never saw a 5.56mm tracer round: It is the same overall length as the ball round.

[JohnKSa]

.223 and 5.56mm cartridge cases have the same dimensions.

Well, to be completely accurate, they're very close, but they're not the same.

[tahunua001]

mine's 5.56 if I ever get another AR it'll be 223 wylde.

[20thru45]

And of course he is correct, I was imprecise, most barrels are stamped with one or more cartridges that the entity that chambered the barrel believes can safely be fired thru their chamber and the barrel.

I believe in strictly observing said stampings unless the obvious is left off such as the ability to safely fire 38 spl in a 357 Mag chamber. I wouldn't recommend it but, it is safe in the short term.

[thallub]

.223 and 5.56mm cartridge cases have the same dimensions.

Well, to be completely accurate, they're very close, but they're not the same.

Sorry, your link does not give the dimensions of the respective cartridge cases. It compares chamber dimensions.

[barnbwt]

barnbwt, re the 77-grain, doesn't it depend on the overall length of the cartridge? Touching the lands is okay, if the powder charge is appropriate for the condition.

I'm not an AR owner, let alone expert, let alone bullet expert (), but I was under the impression those heavy bullets had a fatter ogive to get some of their weight (as opposed to simply being longer inside the case). If so, that fatter ogive will contact the lands sooner.

I read through the giant article linked earlier by the guy basically debunking the thermonuclear implications of cross-loading 223 and 5.56. I highly recommend anyone interested read it, it was very well done, well thought out, and had very clear logic (and wasn't trying to sell anything). The thrust was that 223 and 5.56chambers overlap each other's tolerances, though 223 tends to be slightly tighter on the spectrum --which raises pressure. The ammunition for NATO is loaded slightly hotter than similarly-weighted SAAMI ammo--again slightly higher pressures, but easily within acceptable limits (16% more bolt thrust, when your safety factor is probably 5 or higher )

I have a couple theories that I think explain the kaboom, super-overpressure, or whatever you call it scenarios surrounding this controversy, in what I think is the order of likelihood;
--Most likely of all; the sum of all fears. Nearly all of the below conspire to screw over a few vocal people and their rifles
--Not paying attention to your OAL will result in the neck swaging into the bullet against the end of the chamber, especially if you can't be bothered to neck-trim between reloads. The chamber spec for 223 in the article was .03" shorter!
--Not paying attention to or checking bullet setback due to either feed ramp or rifling lands contact, likely stemming from insufficiently crimped reloads. Freebore of 223 was about .02" shorter--unlikely to cause dangerous setback, but would contribute to it as well as resisting the bullet's initial movement slightly more.
--Thinking that 5.56 is a hotter round than it is and getting ambitious with reloads (and the reverse for 5.56 rifles kaboomed with 223)
--Trying to reload 5.56 to save money over cheap surplus and getting careless/sloppy/cheap in production
--Shooting cheap steel surplus which only comes in the 5.56 flavor, and the whole can of worms regarding the safety or not of that case material
--Defective cheap factory/surplus ammo made by irate monkeys laid off by Century still suffering delirium tremens
--Whatever it is named, a tight chamber is a tight chamber, and will raise pressures somewhat
--Happenstance. Flaw in a case-wall, high powder temperature, powder degradation, phase of the moon, and any number of other things that normally won't combine to do you harm

And lastly, one socio-economic explanation that is so obvious it deserves mention. SAAMI controls the specs, SAAMI isn't trying to push cheap milsurp ammo produced by non-members (or years ago). AR's rise to prominence after the AWB, and cheap bastage shooters use cheap milsurp ball. SAAMI member companies want some of that fat money cake, and increase civilian production of ammo. New production isn't cheaper, since it wasn't already paid for eons ago by Uncle Sugar, so new production lags in sales. SAAMI cooks up story about how shooting anything not produced by their member companies will destroy your gun, offering so little definitive evidence or proof to back up their claim that we debate it to this day.

And the dominoes fall like a house of cards. Checkmate.

This would also explain why the dire warning only surfaced after 5.56 usage was widespread, even though both cartridges had been cross-used for decades before by smaller numbers of shooters without sufficient cause for alarm.

TCB

[JohnKSa]

Sorry, your link does not give the dimensions of the respective cartridge cases. It compares chamber dimensions.

Fair enough.

The cartridge dimensions are the same but the cases are not identical. There are small differences in the way the shoulder is formed.





Different cartridges (very slightly different), different chamber dimensions, different leade, different loading conventions. One can argue that they're interchangeable (although in the face of a number of established experts who have evidence to the contrary), but it's really not possible to argue rationally that the two cartridges are the same.

SAAMI cooks up story about how shooting anything not produced by their member companies will destroy your gun, offering so little definitive evidence or proof to back up their claim that we debate it to this day.

1. It's not only SAAMI recommending against it.
2. There's plenty of evidence/proof, but too many people want things to be black and white.

If a few rounds of 5.56 doesn't turn a .223 rifle into a grenade they're convinced that there can't possibly be an issue. The real world isn't like that. Designs have safety margins, measurements have tolerances, and conditions vary. So lots of people get away with the mismatch because it's not a huge mismatch and people who don't understand the difference between improbable and impossible decide that is proof enough that there isn't an issue at all.

If you read my earlier post on the first page of the thread, you'll find predictions by the experts of what can happen if one ignores the mismatch warning. You'll also find examples where exactly what was predicted happened.

Will it happen every time? Nope. I doubt it will happen very often for that matter. But it can happen and it does happen.

5.56 vs .223 – What You Know May Be Wrong

Very good article. He mirrors what the experts say is likely to happen with a mismatch which is what I stated in my earlier post. Blown/pierced primers if the tolerances stack up the wrong way.

... debunking the thermonuclear implications of cross-loading 223 and 5.56.

I don't know of anyone with any decent credentials or experience that has stated outright that the likely consequence of a .223/5.56 mismatch would be a catastrophic failure. However, the fact that it seems quite unlikely to actually blow up a gun isn't sufficient rationale for saying that there's no problem at all. A blown primer may not be a severe as a blown up gun, but it's not a complete non-issue either.

As an interesting postscript, I just finished reading a new product release notice. Black Hills is introducing an "Optimized 5.56mm 62gr TSX" loading. The product release includes the following notice:

"This 5.56mm ammunition is loaded to pressure higher than commercial .223 ammunition and should be used only in suitably chambered firearms."