As an Amazon Associate, this site earns a commission from Amazon sales.











September 25th, 2021

.223 Rem vs. 5.56x45mm NATO — What You Need to Know

.223 Rem Remington 5.56 SAAMI CIP 5.56x45 5.56x45mm NATO cartridge ammo pressure test luckygunner ultimatereloader Gavin Gear

Probably the most popular centerfire rifle round in the Western Hemisphere is the .223 Remington and its metric match, the 5.56x45mm. Though many folks use “.223 Rem” and “5.56×45″ interchangeably, there are some meaningful differences in specifications for the original .223 Rem and the 5.56x45mm cartridge, as adopted by the U.S. military and NATO armies. The default chamber throats are slightly different and the .223 Rem is rated at 55,000 PSI vs. 62,366 PSI for the 5.56x45mm.*

.223 Rem vs 5.56x45mm — Key Differences
There is a truly outstanding, very thorough article on the subject, published by LuckyGunner.com.** This involved extensive testing, with pressure monitors, of 5.56x45mm ammo in .223 Rem chambers. Those tests revealed the peak pressures. Here is one of the ammo test charts:

.223 Rem Remington 5.56 SAAMI CIP 5.56x45 5.56x45mm NATO cartridge ammo pressure test luckygunner ultimatereloader Gavin Gear

NOTE: “The observed chamber pressure for Federal XM855 5.56mm ammunition in a .223 Rem chamber exceeded .223 maximum pressures, but not by a massive amount. The ninth shot (the red line) was an underpowered cartridge which exhibited significantly lower velocity and pressure than the other rounds, so it was excluded from the average velocity and pressure numbers for this chamber.”

And if you’re curious, LuckyGunner also fired .223 Rem ammo in a 5.56x45mm NATO-chambered AR15 rifle. As you would expect, the peak pressures were significantly lower, but the .223 Rem ammo still cycled the semi-auto AR-platform rifle perfectly well:

.223 Rem Remington 5.56 SAAMI CIP 5.56x45 5.56x45mm NATO cartridge ammo pressure test luckygunner ultimatereloader Gavin Gear

READ FULL LuckyGunner .223 Rem vs. 5.56x45mm ARTICLE »

UltimateReloader.com Explains .223 Rem vs. 5.56x45mm
To explain the key differences between the .223 Rem and 5.56x45mm cartridges our friend Gavin Gear of UltimateReloader.com has created a very thorough 12-minute video. This covers the cartridge specifications and explains key considerations for hand-loaders. Gavin also addresses the oft-asked question “Can I shoot 5.56x45mm ammo in my .223 Rem chamber?” Gavin’s video is definitely worth watching. In fact, this is one of the most popular videos Gavin has ever created — it has been watched nearly 4.5 million times on YouTube.

What Exactly Is the 5.56x45mm NATO Cartridge?
The 5.56×45mm NATO is a rimless bottle-necked intermediate cartridge family standardized by NATO with development work by FN Herstal. It consists of the SS109, SS110, and SS111 cartridges. Under STANAG 4172, it is a standard cartridge for NATO forces as well as many non-NATO countries.

Bullet diameter: 5.70 mm (0.224 in)
Maximum pressure (EPVAT): 430.00 MPa (62,366 psi)
Maximum pressure (SCATP 5.56): 380.00 MPa (55,114 psi)
Case length: 44.70 mm (1.760 in)
Rifling twist: 178 mm or 229 mm (1 in 7 in)
Parent case: .223 Remington (M193)

Ammo-Maker Federal Premium Compares .223 Rem and 5.56x45mm
Here is a video from ammo-maker Federal Premium explaining the difference between .223 Remington and 5.56x45mm NATO. Federal states that you may experience excessive pressures when firing a 5.56x45mm in a standard .223 Remington chamber:

One leading gunwriter has addressed the question of shooting 5.56x45mm ammo in .223 Rem chambers. He advocates caution (for more info, SEE pressure tests by LuckyGunner.com):

“I have received a slew of questions — many from first time AR-type rifle buyers — about the .223 Rem and the 5.56×45 mm NATO cartridges. Can I shoot 5.56×45 mm NATO in my .223 and vice-versa? Are these the same cartridge?

Externally, the two cartridge cases are identical. The main differences are that 5.56×45 mm NATO operates at a higher chamber pressure (about 60,000 PSI versus 55,000 PSI on the .223 Rem.) and the 5.56’s chamber is slightly larger than that of the .223 Rem. Also, the throat or leade is longer in the 5.56×45 mm chamber. What does this mean? You should not shoot 5.56×45 mm NATO out of a rifle that is chambered in .223 Rem [with a standard short throat]. And be aware that some .223 Rem ammunition will not reliably cycle through some AR-style .223 Rem rifles, but it usually does. As a matter of fact, I have not encountered any difficulty with current .223 Rem. loads cycling through a 5.56 mm AR-style rifle.” — Mark Keefe, Editor, American Rifleman


* According to the official NATO proofing guidelines, the 5.56×45mm NATO case can handle up to 430.0 MPa (62,366 psi) piezo service pressure. The U.S. SAAMI lists Maximum Average Pressure (MAP) for the .223 Remington cartridge as 55,000 psi (379.2 MPa) piezo pressure with deviation of up to 58,000 psi (399.9 MPa). The chamber for military 5.56×45mm NATO has a longer throat prior to the bullet contacting the rifling which results in lower pressures when firing 5.56×45mm NATO ammunition. If 5.56×45mm NATO is used in rifles chambered for .223 Remington the bullet will be engraving the rifling when chambered. which can increase pressures past SAAMI Max levels. NOTE: The C.I.P. standards for the C.I.P. civilian .223 Remington chamber are much closer to the military 5.56×45mm NATO chamber.

** The full-length LuckyGunner article is well worth reading. It even provides specifications for a number of .223 Rem reamer types, and compares the original .223 Rem, the 5.56x45mm NATO, and the modern .223 Wylde chamberings.

Permalink Bullets, Brass, Ammo, Reloading, Tactical, Tech Tip No Comments »
January 3rd, 2014

Texas and California Lead Online Ammo Sales

Texas is a haven for hunters and shooting enthusiasts, so we’re not surprised that the Lone Star State leads the nation in online ammo sales. However, you might be surprised that California, with its liberal, anti-gun politicians, is a close second. Yes, California was the second-most active source of online ammo purchases in 2013, according to statistics from LuckyGunner.com, one of the nation’s leading online ammo vendors. In fact, California was number one in 2012. For 2013, Texas edged California for the top spot, followed by Florida, Michigan, and (surprise) New York.

online ammo sales

online ammo sales

More Online Ammo Buyers are Using Mobile Devices (Tablets and Smart Phones)
More and more people are connecting to the internet via mobile devices. And, apparently, they are using those devices to shop for ammo. Luckygunner.com saw a significant increase in orders from mobile devices in 2013. Fully 22.7% of Luckygunner’s visits were made via mobile devices in 2013, compared to 18.8% in the preceding year. AccurateShooter.com has seen a similar rise in the number of visitors connecting to our site via mobile devices (particularly smartphones).

online ammo sales

Permalink Bullets, Brass, Ammo, News 1 Comment »
January 9th, 2013

LuckyGunner.com Conducts “Epic Ammo Torture Test”

LuckyGunner.com, a leading online ammo vendor, has conducted a remarkable “torture-test” comparison of brass-cased and steel-cased .223 Rem ammunition. Four different kinds of ammo (one brass-cased, three steel-cased) were fired through four different Bushmaster AR15s — ten thousand (10,000) rounds PER GUN. The idea was to see if brass-cased ammo was better than the cheaper, steel-cased ammunition. During the course of the project, Luckygunner’s testers logged malfunctions and checked for accuracy, chamber pressure, gas port pressure, chamber wear, and overall barrel wear. At the end of the test, the well-worn barrels were sectioned to see the effect of thousands of rounds… and the results weren’t pretty.

Luckygun.com Epic Ammo Test

Test Findings: For a multitude of reasons, the test crew determined that Federal brass-cased ammo was “healthier” than steel-cased ammo. The brass-cased ammo shot more accurately, had far fewer malufunctions, and produced less barrel wear. The USA-made brass-cased ammo also showed more consistent velocities. CLICK HERE to READ FULL TEST.

Watch the video below for a summary of results:

Torture Test Procedure
Four types of .223 Rem ammo were tested: Federal brass-cased 55gr FMJBT; Wolf steel-cased (polymer coating) 55gr FMJ; Tula steel-cased (polymer coating) 55gr Bi-Metal Jacket; Brown Bear steel-cased (lacquer coating) 55gr Bi-Metal Jacket. Each ammo type was paired with a specific Bushmaster AR-15. Tests were performed at various round-count stages:

  • At the start: record accuracy, velocity, chamber and gas port pressures, make chamber cast
  • After 2,000 rounds: record accuracy, velocity
  • After 4,000 rounds: record accuracy, velocity
  • After 5,000 rounds: record throat erosion, make chamber cast
  • After 6,000 rounds: record accuracy, velocity
  • After 8,000 rounds: record accuracy, velocity
  • After 10,000 rounds: record accuracy, velocity, chamber and gas port pressures, throat erosion, extractor wear, chamber cast, barrel wear, make chamber cast.

During testing, rifles were cleaned according to a preset schedule and temperatures were monitored. After testing, LuckyGunner sectioned the barrels and made careful inspections.

Click the links below for specific data, test results, and conclusions:

During the testing process, all malfunctions of each rifle-ammo combination were logged. The brass-cased Federal ammo was the clear winner:

Federal: 10,000 rounds, 0 malfunctions.
Brown Bear: 10,000 rounds, 9 malfunctions
(5 stuck cases, 1 mag-related failure to feed, 3 failures to cycle.)
Wolf: 10,000 rounds, 15 malfunctions (stuck cases)
Tula: DNF (6,000 rounds in alternate carbine, 3 malfunctions)

Luckygunner.com Ammo Test 5.56 .223 RemBarrel Wear and Throat Erosion
Some of the barrels didn’t make it to 10,000 rounds: “The steel cased/bimetal jacketed ammunition caused accelerated wear to the inside of their respective bores. While the barrel of the Federal carbine had plenty of life left, even after 10,000 rounds … the Wolf and Brown Bear barrels … were completely shot out by 6,000 rounds. At the end of the test, the chrome lining of the Wolf and Brown Bear barrels was almost gone from the throat forward, and the barrels had effectively become smoothbores[.] A throat erosion gauge could be dropped into the bore from the muzzle end with absolutely no resistance.”

Permalink Bullets, Brass, Ammo 4 Comments »