GUNS AMMO: Federal XM193BK 5.56 - $269.99/case - NOW SHIPPING!

Quote from stamp0101 : You can shoot 5.56 in a gun chambered in 5.56 or 5.56/.223. You can shoot .223 in a gun chambered in .223 or 5.56/.223. You can shoot .223 in a gun chambered in 5.56, but you CANNOT shoot 5.56 in a gun chambered for JUST .223. Most AR platforms can shoot either. But do not shoot 5.56 in your .223 scoped hunting rifle. The 5.56 round has a slightly different shape and higher pressure and can damage a gun that's only made to shoot .223. If you're shooting an AR - you are fine with either round.

please do not take this advise!

Not all AR's have a 5.56 chamber. Yes you might be able to chamber a 5.56 round in a .223 chamber, and yes it may fire, but it also might just blow up in your face.

as others have said, there is a difference, both in case dimensions and SAAMI max allowable chamber pressures.

.223 for .223 guns period

OP - Good find, it's refreshing to see ammo prices go down for once

Quote from bob503 : whats with the 'x' designation?

"X" means it is a factory second. Your friend Bill Clinton signed into law that military rounds from Lake City/Winchester could not sell any military surplus to civilians. They get around this by selling ammo that is not acceptable to the military for a whole bunch of different reasons, too slow, too fast wrong color on M855.

So when you see XM855 or XM193, you will know what the "X" means.

http://ammo.ar15.com/ammo/project...93mil.html

Most manufacturers who market "Mil-Spec" M193 like ammo are either taking "factory seconds" that would otherwise go to the military and packaging them for civilian sale or reducing the second inspection of rounds before distribution. Ammo destined for the government is tested in lot batches and the entire lot is rejected if the batches fail spec tests. Generally, this ammo is still excellent for both plinking and defensive use. XM193 and Q3131a in particular are exceptional rounds for all around civilian use and still show very reliable function in AR15s.

Some AR15ers have noticed, however, that sealant or other small details are sometimes lacking for some lots of these rounds. Sealant in particular is not a critical component to average civilian sales and therefore if sealant problems develop in M193 rounds destined for military contracts (and therefore out-of-spec rounds) they are usually sold as civilian versions of M193 (e.g. XM193). It should be pointed out that this is no reason whatsoever to avoid these rounds.

If you are really concerned about sealant or intend to use the rounds for long-term storage or quasi-military use where they are likely to see harsh and moist conditions do some testing on random samples of your lot for sealant.

Quote from kray_z_dawg : Hate to sound like a noob, but what's the advantage of shooting something like this (5.56) compared to .223, assuming barrel is chambered to 5.56 of course?

http://ammo.ar15.com/ammo/project/hist_diff.html


In the 1950's, the US military adopted the metric system of measurement and uses metric measurements to describe ammo. However, the US commercial ammo market typically used the English "caliber" measurements when describing ammo. "Caliber" is a shorthand way of saying "hundredths (or thousandths) of an inch." For example, a fifty caliber projectile is approximately fifty one-hundredths (.50) of an inch and a 357 caliber projectile is approximately three-hundred and fifty-seven thousandths (.357) of an inch. Dimensionally, 5.56 and .223 ammo are identical, though military 5.56 ammo is typically loaded to higher pressures and velocities than commercial ammo and may, in guns with extremely tight "match" .223 chambers, be unsafe to fire.

The chambers for .223 and 5.56 weapons are not the same either. Though the AR15 design provides an extremely strong action, high pressure signs on the brass and primers, extraction failures and cycling problems may be seen when firing hot 5.56 ammo in .223-chambered rifles. Military M16s and AR15s from Colt, Bushmaster, FN, DPMS, and some others, have the M16-spec chamber and should have no trouble firing hot 5.56 ammunition.

Military M16s have slightly more headspace and have a longer throat area, compared to the SAAMI .223 chamber spec, which was originally designed for bolt-action rifles. Commercial SAAMI-specification .223 chambers have a much shorter throat or leade and less freebore than the military chamber. Shooting 5.56 Mil-Spec ammo in a SAAMI-specification chamber can increase pressure dramatically, up to an additional 15,000 psi or more.

The military chamber is often referred to as a "5.56 NATO" chamber, as that is what is usually stamped on military barrels. Some commercial AR manufacturers use the tighter ".223" (i.e., SAAMI-spec and often labeled ".223" or ".223 Remington") chamber, which provides for increased accuracy but, in self-loading rifles, less cycling reliability, especially with hot-loaded military ammo. A few AR manufacturers use an in-between chamber spec, such as the Wylde chamber. Many mis-mark their barrels too, which further complicates things. You can generally tell what sort of chamber you are dealing with by the markings, if any, on the barrel, but always check with the manufacturer to be sure.

Typical Colt Mil-Spec-type markings: C MP 5.56 NATO 1/7

Typical Bushmaster markings: B MP 5.56 NATO 1/9 HBAR

DPMS marks their barrels ".223", though they actually have 5.56 chambers.

Olympic Arms marks their barrels with "556", with some additionally marked "SS" or "SUM." This marking is used on all barrels, even older barrels that used .223 chambers and current target models that also use .223 chambers. Non-target barrels made since 2001 should have 5.56 chambers.

Armalite typically doesn't mark their barrels. A2 and A4 models had .223 chambers until mid-2001, and have used 5.56 chambers since. The (t) models use .223 match chambers.

Rock River Arms uses the Wylde chamber specs on most rifles, and does not mark their barrels.

Most other AR manufacturers' barrels are unmarked, and chamber dimensions are unknown.


Opinion: In general it is a bad idea to attempt to fire 5.56 rounds (e.g., M193, M855) in .223 chambers, particularly with older rifles.


Fact: SAAMI specifically warns against the use of 5.56mm ammo in .223 chambers. The .223 SAAMI specification was originally made with bolt rifles in mind.
For more see the SAAMI website ammo warning.


5.56 v. .223 Remington specification.

TU for gun ammo SD

Quote from kennedyusmc : You have no idea what you're talking about. Chamber pressure (derived from charge of the ammo -which 5.56 is much higher), gas port size, barrel length, barrel twist, buffer weight, and recoil spring coefficient all affect how a stoner based gas operated rifle will cycle. Sure, any AR will fire a .223 round once, but .223 often does not produce enough chamber pressure to fully cycle the action and load the next round (semi auto), depending on the factors above. Some AR's will shot both reliably, some will not... I have several 14.5in 1:7in twist barrels (or shorter on AR pistols) that are tuned with stiffer recoil springs and heavy buffers... they kick like bb guns and run 5.56 just fine, but with quality .223 they become bolt action rifles. ... and again, .223 creates dramatically less chamber pressure. Less pressure = less round velocity. Less round velocity means less "fragmentation range". You keep shootin .223, I'll take comfort shooting NATO. ... and this is a great deal. XM193 hasn't been this cheap since 2007. (bout 260 delivered/case then)

its still talk.. I would love to see proof.

I just did a quick search & Federal XM193 55g (5.56 NATO) ammo produces a chamber pressure of 55000psi.
http://www.federalpremium.com/res...xm193.aspx

The pressure data is a little less available for .223 ammo but if you look at the reload charts for a 55g FMJ .223 ammo it says to reload to 54250psi.
http://www.accuratepowder.com/wp-...ta_3.5.pdf

Also if you look at muzzle velocity for a 223 vs a 5.56 there essentially the same. ~3200fps for a standard 55g FMJ round. Which leads me to believe that the chamber pressure is essentially the same.

Just bought the Sig 556 chambered in 5.56 that was listed on SD in Jan. This will go great with my new rifle. In for a box. Thanks op.

Quote from Camtender : "X" means it is a factory second. Your friend Bill Clinton signed into law that military rounds from Lake City/Winchester could not sell any military surplus to civilians. They get around this by selling ammo that is not acceptable to the military for a whole bunch of different reasons, too slow, too fast wrong color on M855. So when you see XM855 or XM193, you will know what the "X" means. http://ammo.ar15.com/ammo/project...93mil.html Most manufacturers who market "Mil-Spec" M193 like ammo are either taking "factory seconds" that would otherwise go to the military and packaging them for civilian sale or reducing the second inspection of rounds before distribution. Ammo destined for the government is tested in lot batches and the entire lot is rejected if the batches fail spec tests. Generally, this ammo is still excellent for both plinking and defensive use. XM193 and Q3131a in particular are exceptional rounds for all around civilian use and still show very reliable function in AR15s. Some AR15ers have noticed, however, that sealant or other small details are sometimes lacking for some lots of these rounds. Sealant in particular is not a critical component to average civilian sales and therefore if sealant problems develop in M193 rounds destined for military contracts (and therefore out-of-spec rounds) they are usually sold as civilian versions of M193 (e.g. XM193). It should be pointed out that this is no reason whatsoever to avoid these rounds. If you are really concerned about sealant or intend to use the rounds for long-term storage or quasi-military use where they are likely to see harsh and moist conditions do some testing on random samples of your lot for sealant.

Mucho Thanks!

In for 2K rounds. Repped

Has anyone received any update yet? The price is $349.99 now.

All,
Here is the latest update after talking to a CSR today, Brownells is heavily backordered on this ammo and it could take months to fulfill all the orders so cross your fingers. The ammo prices are on the rise too. It's the year of the election so here we go again.

Latest update (As of April 11):

With such a high demand of this popular ammo we are experiencing delays by the factory in shipping this ammo to Brownells within the appropriate time. With our last inquiry to the manufacturer they informed us that the ammo will be delayed due to production running behind.


Our estimate date of arrival, but never a guarantee is late spring to early summer.

Quote from lizardman162006 : Latest update (As of April 11): With such a high demand of this popular ammo we are experiencing delays by the factory in shipping this ammo to Brownells within the appropriate time. With our last inquiry to the manufacturer they informed us that the ammo will be delayed due to production running behind. Our estimate date of arrival, but never a guarantee is late spring to early summer.

Thanks for the update. I increased my quantity on backorder; the price looks better every day.

Latest update: CSR said XM193 is "trickling in as we speak." I increased my quantity one more time.

they changed my order. something about not having supply to meet orders. I ordered back on Feb 13