Lake City 5.56 lot 7 m193

MapleSugar said:
You'd better brush up on your reading comprehension and read it again. CAREFULLY.

You clearly don't know WTF you're talking about.
Click to expand...

Right then. Let me walk you through it...

.223 Remington vs. 5.56x45--Chambering
and Throat
Considerations
Is the .223 Remington the same as the 5.56x45? The answer is yes and no. There ARE differences between the .223 Remington as shot in civilian rifles and the 5.56x45 in military use. While the external cartridge dimensions are essentially the same, the .223 Remington is built to SAAMI specs, rated to 50,000 CUP max pressure, and normally has a shorter throat.
*but not always* The 5.56x45 is built to NATO specs, rated to 60,000 CUP max pressure, and has a longer throat, optimized to shoot long bullets. That said, there are various .223 Remington match chambers, including the Wylde chamber, that feature longer throats. Military 5.56x45 brass often, but not always, has thicker internal construction, and slightly less capacity than commercial .223 Rem brass.
*I have just finished explaining to you above that this is very unlikely to be the case with any 5.56 you are to encounter. I'm not sure why you'd believe I'm trying to blow smoke up your a$$ over it, but believe what you'd like - or better yet, don't believe me and section cases for yourself*
Should you be worried about shooting 5.56x45 milspec ammo in a .223 Remington? The answer really depends on your chamber. 5.56 x45 ammo is intended for chambers with longer throats. If you shoot hot 5.56x45 ammo in short-throated SAAMI-spec chambers you can encounter pressure issues. The new long-throated 'Wylde' chamber allows safe use of military ammo. Wylde chambers are quite common in Rock River guns. Other manufacturers, such as Fulton Armory, offer modified "match chambers" with extended throats that allow safe use of 5.56x45 ammo in .223 Remington rifles. For a complete discussion of the .223 Rem vs. 5.56x45 question, read this Tech Notice from Winchester, and this GunZone Commentary by Dean Speir. Without belaboring the point, we'll repeat the official SAAMI position: "Chambers for military rifles have a different throat configuration than chambers for sporting firearms which, together with the full metal jacket of the military projectile, may account for the higher pressures which result when military ammunition is fired in a sporting chamber. SAAMI recommends that a firearm be fired only with the cartridge for which it is specifically chambered by the manufacturer."


They are clearly discussing the differences in chambers.
They also mention you can have higher pressures with tighter chambers.
Guess what Einstein, you can have a chamber on gun 'A' that is cut and marked '.223' that is tighter than another gun 'B' that is also marked '.223'
It doesn't mean it spells disaster, nevermind unsafe.

As with the brass sectioning though, don't believe me - go get yourself a chronograph and chart some of this stuff for yourself like I have done.
When you start shooting Winchester White box that is marked '.223' on the side next to Lake City M855 marked 5.56 ammo and see higher velocities and more pronounced pressure signs, scratch your head and think back to this thread.....;)
 
The only thing I'm convinced of is that you tend to ignore anything that contradicts your assertions.:rolleyes:

Instead of focusing on the word "chamber" while ignoring how it relates to the rest of the sentence and paragraph, I've highlighted some of the glaring similarities from each article.

Here is the information from Cheaper Than Dirt:

Is 5.56mm safe in my .223 Remington?

The .223 Remington is a sporting cartridge with the same external dimensions as the 5.56x45mm NATO military cartridge. It is loaded with a .224" diameter, jacketed bullet, with weights ranging from 40 up to 90 grains, though the most common load by far is 55 grains.

The primary differences between .223 Remington and 5.56 x 45 mm (NATO) are that .223 Remington is loaded to lower pressures and velocities compared to 5.56 NATO and the 5.56 NATO chamber has a longer leade. .223 Remington ammunition can be safely fired in a 5.56 NATO chambered gun, but the reverse can be an unsafe combination. The additional pressure created by 5.56 NATO ammo will frequently cause over-pressure problems such as flowing brass, difficult extraction, or popped/punctured primers, but in extreme cases, could damage or destroy the firearm. Chambers cut to .223 Remington specifications have a shorter leade (throat) area as well as slightly shorter headspace dimensions compared to 5.56 NATO "military" chamber specs, which contributes to the pressure issues.

While the 5.56 NATO and .223 Remington cartridges are very similar, they are not identical. Military cases are made with thicker brass in the web area than commercial cases, which reduces the powder capacity (an important consideration for handloaders), and the NATO specification allows a higher chamber pressure. Test barrels made for 5.56 NATO cartridge measure chamber pressure at the case mouth, as opposed to the SAAMI (Sporting Arms and Ammunition Manufacturer’s Institute) location. This difference accounts for upwards of 20,000+ psi difference in pressure measurements. That means that advertised pressure of 58,000 psi for 5.56 NATO, is around 78,000 psi tested in .223 Remington test barrels. SAAMI .223 Rem Proof MAP is 78,500 psi so every 5.56 NATO round fired is basically a proof load, potentially very dangerous. The 5.56 NATO chambers, also known as mil-spec chambers, have a longer leade, which is the distance between the mouth of the cartridge and the point at which the bullet engages the rifling of the barrel. The .223 Remington chambering, known as the "SAAMI chamber", is allowed to have a shorter leade, and is only required to be proof tested to the lower SAAMI chamber pressure. To address these issues, various proprietary chambers exist, such as the Wylde chamber, used by Rock River Arms or the Armalite chamber, which are designed to handle both 5.56 NATO and .223 Remington equally well.

Using commercial .223 Remington cartridges in a 5.56 NATO chambered rifle should work reliably, but generally will not be as accurate as when fired from a .223 Remington chambered firearm due to the excessive leade. Using 5.56 NATO mil-spec cartridges (such as the M855) in a .223 Remington chambered firearm can lead to excessive wear and stress and even be unsafe, and the SAAMI recommends against the practice. Some commercial fireams marked as ".223 Remington" are in fact suited for 5.56 NATO, such as many commercial AR-15 variants and the Ruger Mini-14, but the manufacturer should always be consulted to verify that this is acceptable before attempting it. Signs of excessive pressure (such as flattening or puncturing of the primers) should also be looked for in the initial testing with 5.56 NATO ammunition.
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Here is the information from 6mmBR:

.223 Remington vs. 5.56x45--Chambering and Throat Considerations
Is the .223 Remington the same as the 5.56x45? The answer is yes and no. There ARE differences between the .223 Remington as shot in civilian rifles and the 5.56x45 in military use. While the external cartridge dimensions are essentially the same, the .223 Remington is built to SAAMI specs, rated to 50,000 CUP max pressure, and normally has a shorter throat. The 5.56x45 is built to NATO specs, rated to 60,000 CUP max pressure, and has a longer throat, optimized to shoot long bullets. That said, there are various .223 Remington match chambers, including the Wylde chamber, that feature longer throats. Military 5.56x45 brass often, but not always, has thicker internal construction, and slightly less capacity than commercial .223 Rem brass.

Should you be worried about shooting 5.56x45 milspec ammo in a .223 Remington? The answer really depends on your chamber. 5.56 x45 ammo is intended for chambers with longer throats. If you shoot hot 5.56x45 ammo in short-throated SAAMI-spec chambers you can encounter pressure issues. The new long-throated 'Wylde' chamber allows safe use of military ammo. Wylde chambers are quite common in Rock River guns. Other manufacturers, such as Fulton Armory, offer modified "match chambers" with extended throats that allow safe use of 5.56x45 ammo in .223 Remington rifles. For a complete discussion of the .223 Rem vs. 5.56x45 question, read this Tech Notice from Winchester, and this GunZone Commentary by Dean Speir. Without belaboring the point, we'll repeat the official SAAMI position: "Chambers for military rifles have a different throat configuration than chambers for sporting firearms which, together with the full metal jacket of the military projectile, may account for the higher pressures which result when military ammunition is fired in a sporting chamber. SAAMI recommends that a firearm be fired only with the cartridge for which it is specifically chambered by the manufacturer."
Click to expand...

So while both articles DO mention your favourite word "chamber" they also explain how the SAAMI maximum specs are 20,000 psi or 10,000 CUP lower than the NATO maximum specifications, that the brass can be thicker with less capacity in the NATO 5.56x45mm and the NATO chamber has a longer leade to facilitate longer bullets.

Coincidentally enough, they also both mention that firing 5.56mm NATO through a rifle with a "chamber" rated for .223 Rem can result in dangerous overpressure. This also happens to correlate to the difference in the leade or "throat" as you referred to it.

I don't know about you, but I can't remember reading in any reloading manual that it is a safe or wise practice to exceed your SAAMI maximum load at all and certainly not by 10,000 CUP.

But wait, I found this little gem of information on the ar15.com forum that even has some nice cut-away pictures and graphs:

http://www.ar15.com/forums/topic.html?b=3&f=118&t=514300&page=1

556natochamberversus223remingtonchamber02.jpg


"...With all other things being equal, the 5.56mm NATO chamber with its longer and shallower angled leade and longer amount of effective freebore will produce less chamber pressure than a .223 Remington chamber, when firing .223 Remington SAAMI Spec ammunition. Because of this, 5.56mm NATO amunition can be loaded to a pressure that would be considered excessive in a .223 Remington chamber, yet acceptable in a 5.56mm NATO chamber. (Pressures are measured using different methods between the two systems.)...

...Here's a very interesting quote posted by Ned Christiansen on M4carbine.net:

". . . In short, you can safely fire all 5.56 AND 223 ammunition in a gun properly chambered for 5.56. You MUST NOT fire 5.56 ammunition in a 223 rifle. As case in point, I fired XM193 5.56 ammunition in a 223 test barrel with average pressures (conformal transducer) of 72,550 psi, and peak pressure registered at 76,250 psi. . ."

Since the SAAMI MAP for the .223 Remington is 55,000 PSI, that puts XM193 fired from a minimum spec .223 Remington chamber at 17,550 PSI over the maximum.


(The following is just a generalization to give a graphical demonstration of concept. DO NOT hold me to the exact numbers as they are not correct and they ignore the difference due to the different methods used to measure chamber pressure.)

Consider the left graph pictured below; M193 fired in a 5.56mm chamber. The pressure is within the MAP limit. Now, take the exact same round, (same powder, same charge of powder) and fire it from a .223 Remington chamber; pictured in the right graph below.

pressurecomparisonm193in223chamber07.jpg


Because the .223 Remington chamber has a shorter and sharper angled leade compared to the 5.56mm chamber as well as a shorter effective free-bore, the bullet engages the rifling sooner in the .223 chamber than it would have in a 5.56mm chamber. This causes the pressure to rise faster, peak sooner and reach a higher (and per SAAMI, unsafe) level than it would have if the round had been fired from a 5.56mm chamber."...
Click to expand...

That being said, you can shoot whatever ammo you want to with your rifle. Hell, you can even dip your rounds in oil and make sure the boltface, chamber and bore are well soaked too.

Meanwhile, I'll take the safe route and try to only fire cartridges that don't generate excess pressure in whatever firearm I may be shooting.

BTW, I was just kidding about the oil. Please tell me you don't lube the s**t out of your firearms. Especially if you run XM193 through a .223 Rem "chamber."
 
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MapleSugar said:
The only thing I'm convinced of is that you tend to ignore anything that contradicts your assertions.:rolleyes:
Click to expand...

I haven't made any assertions that SAAMI specifications are NOT different than 5.56x45mm NATO (or any other 5.56mm ammunition for that matter).
Not Chamberings, and not tested pressures.

If you go back to my original post in the thread I called B/S to the assertion that the external dimensions are different and the case wall thickness is increased on the 5.56.
.223 and 5.56x45 cases are the same in external dimensions, and in every case I've seen the internal dimensions are near on identical too.

Back to chamberings:

Something you need to keep aware of though is that while SAAMI can spec. a chamber dimension, that doesn't necesarily mean your 700 (or whatever rifle) with .223 marked on the side meets that specification exactly.

Chamber reamers wear as they are used from barrel to barrel at the factory, and chambers errode with use.

Pressures:

Not that surplus ammo is in abundance anymore, but ever wonder why seemingly perfectly good ammo is released as surplus and put for sale in the first place? It may have exceeded a shelf life, been an overrun of production, or it may have not met the specification in the first place (and other reasons too). Chew on that for a bit and you can see there is quite a lot of variable with that alone.

NATO v. SAAMI - Two Engineering standards, that are not compatable. The two tests are not comparing apples to apples. I wouldn't argue this is reason not to believe NATO spec'd ammo is not hotter; in most every case it probably is. What I do challenge is the notion that this then must mean NATO spec'd ammo is unsafe in all .223 chambers. I think that is a bit of a stretch, and in more than a few instances, patently false.
The problem of course is no Engineer in the know that has any notion of self preservation will come out and say it. They tow the line because that is the safe and prudent thing to do.


For the record, I down-load most all my ammunition because
a) In most instances I can get as good or better accuracy with slightly cooler loads
b) It's easier on barrels
c) It is ever-so-slightly cheaper on powder
d) It is prudent to do so.;)
 
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