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There are two major types of centerfire rifle cartridges available on the market today:

  • Those which are loaded with steel, and
  • Those which are loaded with brass

This seemingly simple variation has caused a never ending stream of argument, discussion, speculation, and questioning from new and seasoned shooters alike.  Complicating the conversation are other variables that typically get lumped into the argument without proper segmentation, such as:

  • The different coating options available on the steel-cased ammo (lacquer or polymer)
  • The different projectile loadings available (copper jacketed lead, the bi-metal coating that most Russian manufacturers use, etc)
  • The different propellant (gunpowder) burn rates

Our team decided to try something ambitious and daunting:  to provide the best resource and data available to answer these questions once and for all through objective experimentation and observation.

We realize this is a lofty and borderline arrogant goal.  We’ve done our best.  Please keep reading to see if you agree.

Here’s what we did:

  • We acquired four identical Bushmaster AR-15 rifles.  We chose the Bushmaster MOE Series AR-15 because it’s a widely available, affordable, and mass-market.  We didn’t want something too cheap and of lower quality or something too expensive and of high quality since our goal is to help the most number of people.
  • We acquired 10,000 rounds each of the following ammunition (new production):
    • Federal 55gr – Brass-Cased – Copper Jacket
    • Wolf 55gr FMJ – Steel-Cased with Polymer Coating – Bi-Metal Jacket (steel and copper)
    • Tula 55gr FMJ – Steel-Cased with Polymer Coating – Bi-Metal Jacket (steel and copper)
    • Brown Bear 55gr FMJ – Steel-Cased with Lacquer Coating – Bi-Metal Jacket (steel and copper)
  • We paired each ammunition type with a specific Bushmaster AR-15 and then fired all 10,000 rounds of it through that particular carbine (except for Tula; more on that below)
  • We systematically observed and tested various things, including (more details below):
    • At the start: accuracy, velocity, chamber and gas port pressures, chamber cast
    • After 2,000 rounds:  accuracy, velocity
    • After 4,000 rounds:  accuracy, velocity
    • After 5,000 rounds: throat erosion, chamber cast
    • After 6,000 rounds:  accuracy, velocity
    • After 8,000 rounds:  accuracy, velocity
    • After 10,000 rounds:  accuracy, velocity, chamber and gas port pressures, throat erosion, extractor wear, chamber cast, barrel wear
  • We logged every malfunction of every rifle-ammo combination
  • The rifles were cleaned according to a preset schedule and temperatures were monitored and kept within acceptable limits (more below)
  • We sectioned the barrels and otherwise made unique observations after the test was complete

If you’re interested in any of the following, you’ll find observations, data, and further details below:

  • Which ammunition was most reliable?
  • Which ammunition was the dirtiest?
  • Which performed better, lacquer or polymer coating?
  • Which ammunition maintained the highest degree of accuracy throughout the test?
  • Which ammunition maintained the most consistent velocity throughout the test?
  • Which ammunition caused the most throat, barrel, and extractor erosion/wear?
  • What effect did the powder burn rates have on bolt cycling?
  • How did the pressure at the gas port vary by ammunition type?
  • How did the pressure at the chamber vary by ammunition type?
  • Which is cheaper to use, after considering all the costs?

What follows is a mind-numbing heap of charts, tables, graphs, images, and data to catalog the entire test, plus a careful analysis of everything we found.  We hope you’ll find it as fascinating as we did.  If you’re in a hurry and just want a brief overview, check out the summary video below.

Test Video Summary

Past Tests

A number of tests have been made public but none offer the depth of information shooters demand.

When considering an undertaking such as this, it’s a good idea to look at what had been done before. There have been a variety of tests conducted using the AR-15/M4/M16 platform over the last 55 years, and we studied as many as possible in order to determine the best course to take.

One of the more notable tests – certainly one of the most discussed – was the Army’s “M4 dust test” of 2007. Much of the public domain information about the test was lacking – were all rifles of new manufacture? Did all firearms use the same magazines? What qualified as a malfunction, and how was each type of malfunction defined? What were some of the details relating to how each rifle functioned, such as cyclic rate of fire? We sought to address each of these concerns in our test.

A test of the MK18 10.5″ CQBR was conducted by Naval Surface Warfare Center Crane and presented at the 2003 NDIA conference. Although the public domain report is rather concise and also focuses on why the weapon itself was created, it contains a lot of useful data such as throat erosion and cyclic rate. The total number of malfunctions is given, but details on when and how each one occurred are not provided, perhaps due to time/length constraints. We borrowed a number of ideas and methodologies from this test, including limits on rate of fire and temperature.

A 2012 collaboration between Tulammo USA and Anderson Manufacturing compared the performance of Federal and Tula ammunition in Anderson Manufacturing carbines. Although malfunctions occurred during the testing, the number of malfunctions was not given.

The Ammunition

For the test, 10,000 rounds each of Federal, Brown Bear, Wolf, and Tula ammunition in caliber .223 Remington were used. Each brand of ammunition used a 55 grain full metal jacketed bullet with a lead core. The Federal 55gr .223 ammunition featured a solid copper jacket and a brass case, while the other three brands used a bimetal (steel and copper) jacket and a steel case. The Brown Bear ammo’s steel case was coated in a green “lacquer,” while the Tula and Wolf cases were coated with a gray polymer.

brass vs. steel cartridges piled up.
It is a commonly held belief that the coatings exist to provide additional lubricity, or “slickness,” to the steel cases. In fact, their primary purpose is to inhibit rust. As the United States Army discovered with a test of steel cased ammunition in the 1960s, uncoated steel cased ammunition was prone to rusting. Due in no small part to the coatings, we had no problems with rust during the test.

The Rifles

Four brand new and identical Bushmaster MOE carbines, Bushmaster model BCWA3F MOE, were used. Each was produced in Ilion, New York at the same facility where Remington rifles are made.

A close shot of an AR-15 rifle's trigger.
Formerly located in Maine, Bushmaster rifles are now produced in New York.

Upper and lower receivers were of standard design and manufactured with 7075-T6 aluminum via the forging process. Receiver extension tubes were commercial pattern and had six adjustment points; receiver endplates were not staked. Buffers weighed 3.0 ounces and conformed to carbine dimensions. Fire control groups were semi-automatic and trigger pull weight varied between 8 and 10 lbs. Bolt carrier groups were machined for semi-automatic use only; gas keys were properly staked.

A stack of AR-15 carbines used in the brass vs. steel testing.
The reciprocating components were fairly standard AR-15 parts which proved to be up to the task.

Barrels were 16” in length, with all other exterior dimensions matching those of the military M4. Front sight bases were attached to the barrels with two taper pins driven from right to left. Barrel exteriors were parkerized after the attachment of the front sight bases.

Gas ports, located at the carbine position, were .058” in diameter. Chambers conformed to 5.56mm dimensions. The rate of twist was 1 turn in 9 inches, and both chambers and bores were chrome lined. Barrel nuts were torqued to inconsistent values: two had been torqued to approximately 5 ft/lbs, while the other two had been torqued within the appropriate range of 30-80 ft/lbs.

The use of Magpul MOE furniture enabled the attachment of sling mounting points and flashlight mounts from Impact Weapons Components designed for the MOE stocks and handguards. The sling mounting points and flashlight mounts remained attached to the firearms without issue throughout the entire test; however, flashlights of the correct diameter installed in the mounts in accordance with provided instructions did not stay in the mounts. Excessive tightening of the mounts’ tension screw did not fix the problem, and the flashlights were set aside for the duration of the testing.

Shooters line up to fire during the brass vs. steel test.
Numerous optics and accessories were used during the test.
Optics used during the high volume shooting portion of the test include the Aimpoint CompM3 in GDI mount as well as the EOTech 552 and XPS 2-0. Backup sights were Magpul MBUS. One MBUS sight cracked and fell off of the carbine to which it was attached due to heating and cooling cycles that negatively affected the polymer material.

Excessive upper receiver heat did cause thermal discoloration of and cosmetic damage to the EOTech sights. Also, one CR123 battery in the XPS 2-0 ruptured – possibly due to heat – but both EOTechs, as well as the Aimpoint, remained functional at the end of the test. The manufacture date of the 552 was April of 2005; prior to the test, its battery spring “grommets” were replaced with a newer design, which markedly improved battery life.

Charging handles used during the test include the standard AR-15 type, the BCM/Vltor Gunfighter, and the Rainier Arms/AXTS Raptor. The majority of rounds (over 20,000) were fired with the Raptor charging handles installed in various weapons. No functional issues were encountered with any charging handle used during the test, and no practical differences were noted between the aluminum and steel latches of the various charging handle types. Most shooters who used the Raptors commented that they appreciated the ambidextrous design during manipulations of the firearms, especially during clearing.

The use of these accessories had no functional impact on the weapons and their use should not be construed as true modifications. With one exception, the results of this test reflect the performance of the carbines in the condition in which they were removed from the box. That exception was the correction of improper torque values found in two of the four test carbines. It should be noted that the carbines were disassembled and reassembled numerous times over the course of the test to allow for the use of Cerrosafe casts of the chambers.

A man prepares to shoot a Bushmaster rifle as part of the test.
The Bushmaster carbines were patterned after the military’s M4 Carbine, with a few changes such as a semi-automatic fire control group, a slower rifling twist rate, a 1.5″ longer barrel, and a lighter bolt carrier.
Only one type of ammunition was fired through each carbine, and the different colors of Magpul MOE furniture made it easier to identify which was which. Throughout the testing, we successfully avoided any “cross-contamination” – in other words, each carbine fired only the ammunition it was supposed to.

The carbine firing the Federal brass cased ammunition, serial number ARA041079, had standard black handguards and stock, the Brown Bear-firing carbine (LBM23712) had olive drab (green) furniture, and the Wolf (LBM21236)and Tula (LBM23157) carbines had flat dark earth (tan) furniture. For simplicity’s sake, the weapons will be hereafter referred to as “the Wolf carbine” or “the Federal carbine,” etc.

AR-15 receivers used to determine if brass or steel is better.

Initial Preparations

Visual Inspection

Each firearm was broken down and inspected to ensure that it was within acceptable standards; this initial visual inspection did not  reveal any deficiencies serious enough to be addressed prior to the beginning of the test. During the first range trip, however, serious accuracy issues were noted with two carbines – the Federal and Brown Bear weapons.

Both shot groups of over 5MOA, or over 5 inches at 100 yards, out of the box. It should be noted that ten shot groups were fired for all accuracy testing in this article, and the results are not directly comparable with three or five shot groups. Because these groups were much larger than they should have been with any factory new ammunition, the rifles were examined.

A target showing the size of a grouping.
All accuracy testing consisted of ten shot groups at 50 yards from a supported position with a US Optics scope at 17x magnification.
The upper receiver assemblies of the two problem carbines were completely disassembled in order to determine the cause of this issue. It was immediately apparent that the problem related to improper barrel nut torque values – the barrel nuts, which slide over a collar on the barrel and thread onto the front of the upper receiver, required less than 5 ft-lbs to break loose.

Proper torque values for this part are 30-80 ft-lbs. Once the components were properly reassembled, ten shot group sizes shrank to approximately 3.5 MOA, which is a realistic result to expect from standard carbines firing bulk ammunition.

Other Tests

Before high volume testing commenced, other tests and observations were conducted in order to gather as much data as possible about the performance of the firearms. These tests include but are not limited to chronograph (velocity) testing, Cerrosafe measurements of internal chamber and bore dimensions, chamber and gas port pressure testing, and high speed video of bolt velocities and cycle times.

These tests were also conducted periodically throughout the testing – accuracy and velocity every 2,000 rounds, Cerrosafe at 5,000 and 10,000 rounds. Most of the firing was conducted at a very fast pace, with up to ten magazines (300 rounds) being fired in a row. Rates of fire did slow at times, especially when accuracy testing was being conducted. However, the rates of fire were identical for the test rifles – if one was fired quickly, so were the others.

Although the shooting was fast and hectic, we did not exceed certain temperature and rate of fire limits – the barrels did not exceed 750 degrees Fahrenheit. Firing was periodically halted to identify the cause of a malfunction, conduct diagnostic tests, or replace parts.

A large dust storm in the Arizona desert that rolled in during the test.
Large dust storms were a regular occurrence during testing. This was the end of the second day of shooting.

Cleaning and Lubrication

A cleaning and lubrication schedule was followed – at 2,500 and 7,500 rounds, the bolt carrier group was wiped down with a paper towel, and at 5,000 rounds, a detailed cleaning was undertaken. A single drop of FireClean lubricant was applied to the cam pin hole of the bolt carrier group every 1,000 rounds, and six drops were used after each of the aforementioned cleaning intervals. Certain small parts were replaced as needed, and they will be discussed later in the article. After all initial tests were complete, the bulk of the shooting commenced.

Brass vs. Steel Results

Which Ammo Was Most Reliable?

The data which will probably be most interesting to everyone who reads this article is how often each riflemalfunctioned. To satisfy that particular thirst, here are the basic results:

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

A man firing a Bushmaster carbine using Federal ammunition successfully shot all 10,000 steel rounds without any malfunctions.
The Bushmaster carbine firing Federal ammunition fired all 10,000 rounds without any malfunctions.

The carbine firing Tula had a case stuck in the chamber after 189 rounds which proved exceptionally difficult to clear, even with the use of a steel cleaning rod after the rifle had cooled. Over the next three hundred rounds, 24 malfunctions – stuck cases and failures to fully cycle, or “short stroking” – were encountered. At this time, the Tula carbine was removed from the testing, as the problems were causing significant delays.

A decision was made to fire the remainder of the Tula ammunition through other carbines. Approximately 300 rounds were fired through an HK416 (no malfunctions), 1,000 through a Spike’s Tactical carbine (3 malfunctions), and 6,000 through a Spike’s Tactical midlength without any cleaning (3 malfunctions). All malfunctions with the other carbines were stuck cases or failures to eject.

After thousands of rounds without cleaning, the internal AR-15 components were... unclean.
After thousands of rounds without cleaning, the internal components were… unclean.

Of the remaining three ammunition brands, the first malfunction encountered was a magazine-related failure to feed at 2250 rounds with the Brown Bear carbine. For the Wolf carbine, the first malfunction occurred at 4850 rounds – a stuck case.

It should be noted that this testing was conducted in the Arizona desert during monsoon season and was frequently interrupted by dust storms which covered the carbines in fine sand as well as rainstorms which drenched them in water. These storms did not affect the previously set cleaning schedule. In addition, the rates of fire were quite high, and the carbines were sometimes fired until they were too hot to touch. These rates of fire were identical for all weapons and they continued to function very well despite the adverse conditions.

A man fires an AR-15 during with heavy raindrops falling.
In addition to dust storms, fairly heavy rain was also encountered during the monsoon season. No malfunctions were encountered during inclement conditions.

At the 5,000 round mark, the bolt carriers, upper receivers, and barrels were cleaned. After observation of high speed video showed inconsistent cycling, action springs ($3) were replaced, as were extractor springs ($6.99) and gas rings ($2.19).

The second half of the test started off with several malfunctions with the Brown Bear carbine – at 5,200 and 5,250 rounds, short stroking malfunctions were encountered. High speed video showed that the bolt was barely coming back far enough to pick up the next round, and occasionally not even far enough to eject the spent case. Additional lubrication did not prevent the second malfunction.

An AR-15 being used to fire Brown Bear ammunition.
Several malfunctions were encountered with the Brown Bear carbine shortly after the 5,000 round mark.

A detailed physical examination revealed previously unnoticed carbon buildup in the gas key and gas tube which had almost completely occluded those components. The other firearms were inspected, and none exhibited carbon buildup which was even remotely close to that of the Brown Bear carbine. Cleaning of these components in the field proved difficult to impossible, and it was decided to set them aside in order to examine the phenomenon.

The gas tube and bolt carrier of the Brown Bear rifle were replaced with identical components, after which firing resumed without incident. No malfunctions occurred until 7,500 rounds, when five stuck cases were encountered between 7,500 and 8,200 rounds. From 7,500 rounds on, a number of cases with distended and/or split necks were observed.

The last malfunction with Brown Bear was a cycling issue similar to the first two, which was the 9,551st round to be fired. A change in report and recoil indicated that the round was possibly undercharged, although the projectile did exit the bore.

Log books and ammo magazines showing how the brass versus steel test was conducted.
Nine malfunctions might sound like a lot, but out of 10,000 rounds fired, that’s only a .09% failure rate. Or, if you’re the optimistic type, a 99.91% success rate.

Two more stuck cases were encountered with the Wolf carbine at 5,800 and 5,850 rounds. No actions were taken, and the next stuck case was not encountered until the round count was over 9,000. From 9,200 to 10,000 rounds, twelve stuck cases were encountered. During this time, a Boresnake was used to superficially clean the bore and chamber; it did not appear to have any effect on the occurrence of malfunctions.

As stated previously, the carbine firing Federal ammo functioned flawlessly from the first round to the last. There is not much else to report in terms of reliability. It just worked.

The table below summarizes the reliability of each manufacturer’s ammunition as well as mean rounds between stoppages (MRBS).

A table indicating the reliability of each manufacturer's rounds.

Which Ammo was Dirtiest?

Of particular concern to some shooters is whether or not one type of ammo is dirtier than another. Imported ammunition is often maligned for being dirty and difficult to clean, and so the lower receivers of each firearm were not cleaned at all from the first shot to the last, in order to see which became the most filthy.

Special attention was also paid to how much effort was required to clean each rifle at the 5,000 round detailed cleaning portion of the test. Here, high-resolution photos of the lowers are available for your perusal.

Interactive photo – mouse wheel or image controls to zoom or hold & drag

This photo allows you to zoom in and see the filthy lower receivers.

Interestingly, the dirtiest lower receiver was that of the Federal carbine. The upper receiver and bolt carrier group assembly of the Federal carbine also took significantly longer to clean than the Brown Bear and Wolf carbines – although it should be kept in mind that the Brown Bear carbine’s gas tube and gas key were so fouled with carbon after 5,000 rounds that it would no longer function reliably. Nearly the same level of buildup was found on the replacement key and tube after they had seen just short of 5000 rounds.

Interactive photo – mouse wheel or image controls to zoom or hold & drag

Another close up view of the the AR-15 lower receivers used in the test.

How was Accuracy Affected?

Although end users of off-the-shelf carbines firing bulk ammo should never expect tack-driving accuracy, group sizes were checked every 2,000 rounds in order to monitor how each type of ammunition was faring. Again, these groups consisted of 10 shots at 50 yards from a supported position, using a US Optics scope at 17x magnification.

A Marine infantryman and marksmanship instructor prepares to test accuracy.
A Marine infantryman and marksmanship instructor prepares to test accuracy.
While the carbine firing Federal ammunition maintained acceptable accuracy up to and including the 10,000 round mark, the Brown Bear and Wolf carbines exhibited significant accuracy loss by the 6,000 round mark. It is quite possible that this first started occurring earlier than 6,000 rounds, because groups at 4,000 were well within standards of 5MOA or less, while some shots at 6,000 “keyholed,” or impacted the target sideways.

A target showing keyholing of ammunition.
Keyholing is not conducive to good accuracy or precision.

Even if we use accuracy as the only factor to determine serviceability, the Federal carbine was by far the best performer in this category. Its barrel was showing wear, but was serviceable right up to the end of the test. The Brown Bear and Wolf barrels would have required replacement at approximately 5,000 rounds, or halfway through the test.
To see accuracy results for each manufacturer at specific intervals of the testing, click through the slideshow below:

 

A chart indicating the accuracy of each manufacturer's ammunition.

Were There Velocity Changes?

In addition to accuracy data, we have chronograph data at 2,000 round intervals. Velocity loss is another sign of a barrel becoming worn out, or “shot out.” However, in this case, it was not an exceptionally reliable indicator of barrel failure, for the Wolf and Federal velocities were fairly close to one another all the way to 10k, while the Brown Bear velocity did decrease in a more significant manner towards the end of the test. A military standard for a barrel being unserviceable is a drop in velocity of 200fps or more.

A chart indicating decreased muzzle velocities as testing went on.

Data Analysis

While the above section is essentially a factual summary of the events which occurred during testing, the following is a logical explanation for the results of the test, based on our experiments/measurements/observations as well as the work of other individuals and organizations in the field.

Why Didn’t Tula Function Well in the Test Carbine?

One of the first questions one might have after reading the above treatise is, “What happened with Tula?”

After all,  it consists of a 55 grain bimetal jacketed lead core projectile loaded in a polymer coated steel case, and this description is by no means an outlier compared to the other ammunition in the test. In terms of velocity, Tula was also in line with the other products. Tula functioned very well in a Spike’s Tactical midlength, which saw 6,000 rounds of Tula without any cleaning and only had three malfunctions.

But in the Bushmaster carbine, Tula was a no-go. In terms of functional problems, there were two major issues with Tula: “short stroking” – a failure of the bolt to fully cycle to the rear – and extraction problems. Further research and experimentation indicated that there was likely one factor which contributed to both failure types.

A chart indicating Tula chamber pressures.

Chamber pressure measurements indicated that Tula had the second highest chamber pressure of any ammunition in the test when all barrels were new, and these results were verified in a separate test barrel which was used for all ammunition types. Federal was highest with a maximum average pressure of 52kpsi and Tula followed with 51kpsi. Wolf registered 47.5kpsi with Brown Bear close behind at 47kpsi.

A chart indicating chamber pressure in the firearm shooting Brown Bear ammo.
Brown Bear’s maximum average chamber pressure was lower than that of Tula, but it functioned better overall.

A chart showing the chamber pressures for the firearm shooting Federal.

Federal’s maximum average chamber pressure was the highest, and it also had a peak which occurred later than the other ammunition types.

A chart indicating Wolf's pressure curve was very similar to Brown Bear.

At the beginning of the test, Wolf’s pressure curve looked very much like Brown Bear’s.

What’s really important in this case, however, is not the maximum chamber pressure number, but powder burn rate and thus gas port pressure. Whether measured in clean, fouled, new, or worn out barrels, Tula exhibited gas port pressures that were 10-20% lower than all other ammunition types.

Basically, the powder burns too fast, and by the time the bullet has reached the barrel, the pressure drops.  The rise time of Tula, defined as the time in microseconds for pressure to rise from 25% to 75% of maximum chamber pressure, is 175ms. In comparison, Federal AE223, depending on temperature, has a rise time of 260-300ms.

A chart showing gas port pressure and rise for each of the manufacturers.

Couple this with the .058″ gas port used on the Bushmaster rifles – about the same as a Colt 6920 with a 16″ barrel, and just about the smallest gas port you’ll see on any 16″ carbine AR-15, and you’re bound to encounter problems. The Spike’s Tactical midlength did not have a small gas port relative to its longer gas system, and so it functioned without any short stroking issues.

A pressure graph for Tula.
The peak pressure and overall curve of Tula ammunition at the gas port were low and flat…
Wolf ammunition's pressure curve.
…while ammunition such as Wolf had higher peak gas port pressures as well as more distinct peaks.

This explains the short stroking issues, for an insufficient gas port pressure for a given gas system length and port diameter would logically cause insufficient bolt velocity – but what about the failures to extract?

Part of the answer to this question is the nature of the case material itself. When heated, steel does not expand and contract the same way that brass does – in fact, brass expands 1.5 times as much as steel. The shape of the .223/5.56 case was designed with brass as the case material; this plus the fact that steel doesn’t expand – and more importantly, contract – like brass means that extraction will be naturally more difficult.

Beyond these differences, though, is it possible that extraction of Tula – and possibly other ammo – could be made easier by adjusting the pressure curve? A clever test conducted by the US Army’s TACOM and presented at NDIA in 2003 may have the answer. Titled “Understanding Extractor Lift in the M16 Family of Weapons,” the test concluded that the extractor lifts off the rim of the case during initial rearward travel, but that residual chamber pressure holds the case against the bolt face until the extractor returns to the case rim.

In other words, if there are pressure curve issues, case extraction – made slightly more difficult by the steel case – becomes questionable, as the extractor may not return to place in time to pull the case out of the chamber. While a drop in Tula’s chamber pressure at the appropriate time is not observed, it is possible that the location of the gauge is not ideal for reading pressures against the bolt face.

We know from the rise time and gas port data that the powder does burn too fast for the system, so it is quite likely that this is a contributing factor to the rate of extraction failures.

A man firing a Bushmaster AR-15.
Tula ammunition is not ideal for AR-15s with small or military spec gas ports.

To be sure, the short stroking failures are a result of low gas port pressure, which is due to a powder burn rate not perfectly matched to that which would be ideal for the AR-15 platform. If you aren’t sure if this ammunition will cycle in your AR-15, buy a few boxes and shoot one round at a time from an otherwise empty magazine. If the bolt does not consistently lock back to the rear, chances are that you will encounter problems with this rifle/ammunition combination.

What Effect Did Coatings Have On Steel Cased Ammo Performance?

A common belief is that the lacquer coating of certain steel cased ammunition will “melt” in the chamber of a hot rifle and cause subsequent rounds to fail to extract. At one point, we might have believed that.

But in this test, we saw three times as many failures to extract  with the polymer coated Wolf brand ammo (15 extraction failures) than with the lacquer coated Brown Bear ammo (5 extraction failures). Although the polymer coated Tula ammunition was fired in different rifles, the rate of extraction failures in those rifles was lower than that of Wolf.

A man fires an AR-15 with laquer coated casings.
There will be a very small number of stuck cases experienced when shooting steel cased ammunition, but we didn’t see a correlation between lacquer coatings and stuck cases.

If anything would make that lacquer coating “melt,” it would be the treatment these rifles received during the test. We shot them until they were too hot to hold – hot enough that a chambered round would cook off in ten to fifteen seconds. We also tried leaving rounds chambered before temperatures reached that point. None of this harsh treatment caused extraction problems.

We found no evidence to back up the claim that lacquer coatings melt in the chamber and cause extraction failures.

Why Did The Barrels Wear The Way They Did?

Certainly one of the most visually striking parts of this article is the inclusion of post-test barrel cutaways. The barrels were cut axially with an angle grinder and then longitudinally by the wire EDM process. This lets us see exactly how the barrels wore throughout the test – and there were significant differences.

The first answer to this question is, “Because we shot them until they got hot, and then we kept shooting them.”

A saw cuts into the barrel of an AR-15 during the steel vs. brass test.
Due to the position of the front taper pin and the effects of extreme heat over time, the front sight base of the Brown Bear carbine had to be cut off before the barrel could be removed from the upper receiver and sectioned.

The rate of fire definitely contributed to rapid barrel wear. Still, there were other factors which played a major role.

Interactive photo – mouse wheel or image controls to zoom or hold & drag

These tight images of the barrel cutaways offer insight into barrel wear.

As indicated by accuracy testing, 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 at extremely high rates of fire, the Wolf and Brown Bear barrels were subjected to the same rates of fire and 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, with the rifling near the muzzles acting only as a mild suggestion on the projectiles. A throat erosion gauge could be dropped into the bore from the muzzle end with absolutely no resistance.

A throat erosion gauge.
This is a throat erosion gauge. It’s not supposed to fit inside the muzzle.

The bottom line is that for both Brown Bear and Wolf, the lands had been completely ground down to the diameter of the grooves. What’s still visible is the differences in material, for the grooves have some chrome lining left. Longitudinal scratches are visible inside the bore, and it is believed that they were caused by the projectiles meandering their way down the bore in a casual manner before exiting and tumbling in a fairly random direction.

Interactive photo – mouse wheel or image controls to zoom or hold & drag

A detailed look at gas port erosion for each of the ammunition manufacturers tested.

However, the gas port of the Federal carbine was far more eroded towards the muzzle than the Wolf or Brown Bear barrels. I believe that this is due to the excessive throat erosion and barrel wear of these two barrels – the Federal barrel maintained a good seal between itself and the bullet up to 10,000 rounds, while the Wolf and Brown Bear barrels let a significant amount of gases past the projectile, reducing the flame-cutting effect on the gas port as time went on.

A chart indicating Brown Bear exhibited secondary pressure spikes and ignition delays at 10,000 rounds.
Brown Bear exhibited secondary pressure spikes and ignition delays at 10,000 rounds.
A pressure curve showing a downward pressure curve with Wolf ammunition.
At 10,000 rounds, Wolf’s pressure curves were about as ugly as they could be and still result in a functioning weapon.

A curved graph showing the decline of gas port pressure for Federal.

Federal ammunition at 10,000 rounds exhibited minor secondary pressure spikes, but the initial rise was not vastly different than the initial testing.

The steel cases themselves don’t have any effect on the condition of the bore. The difference lies with the projectile – the soft copper jacket of the Federal ammunition simply doesn’t cause the same amount of wear as the bimetal (copper and steel) jacket of the Russian ammunition.

A graph detailing troat erosion in LuckyGunner's brass vs. steel test.
For this measurement, throat erosion was measured in thousandths of an inch from a specific point forward of the case mouth. At 10,000 rounds, the Wolf and Brown Bear throats had eroded to a point which could not be easily measured. The diameter of the entire bore had become enlarged.

Firing continued for the Wolf and Brown Bear carbines after their barrels had been shot out in order to collect other data and finish the test. However, Tula firing was halted at 6,000 rounds from the backup Spike’s Tactical midlength.

The data from this weapon cannot be directly compared to the others, due to differences in construction (the barrel had a midlength gas port, was manufactured via the hammer forging process, and featured “extra thick” chrome lining) and methodology (it was fired with only reliability testing in mind and saw even higher rates of fire as well as environmental abuse such as mud, water, and dirt testing). Still, general conclusions can be drawn, even if direct comparisons cannot.

The barrel of the Spike’s Tactical midlength shot acceptable groups at 4,000 and 5,000 rounds, after it saw seventeen magazines of 30 rounds dumped through it several times, but by 6,000 rounds, it too was keyholing. The changes in barrel construction did not appear to offer a massive advantage in terms of barrel life, while changes in ammo – to copper jackets only – did. Performance indicators for the Federal barrel show that it would likely have remained serviceable for at least another three to five thousand rounds when it was sectioned after 10,000.

An important factor to consider is that in the real world, barrels are wear items. They will eventually become unserviceable if shot enough. If you plan on shooting a lot, don’t get too attached to your barrel – think of it as a thing that does a job for a certain period of time at a certain cost. When that time is up, change the barrel. The AR-15 is a modular platform, and barrel changes are quite simple.

Think of it this way – if a barrel A costs 50-100% more than barrel B but only delivers the same level of accuracy for 0-50% more time, isn’t it a more financially sensible decision to shoot through more examples of barrel B?

The high speed video below offers a comparison of each firearm’s cyclic rate as testing continued.

Did The Steel Cases Break or Wear Down The Extractors?

Different wear patterns were evident on the extractors after 10,000 rounds had been fired. Given that most of the extraction failures with the steel cased ammunition brands occurred during the last half of the test, it is possible that a replacement of the extractors at the halfway point or later would have reduced the number of failures to extract. These wear patterns were not easily visible with the naked eye, only becoming obvious with the aid of macro photography.

If you regularly shoot steel cased ammunition, it might be a good idea to replace your extractor along with your barrel, or at 5000 rounds, whichever comes first. Replacement extractors are not very expensive. Changing the extractor spring at the same time would require no additional work – just set aside the old extractor and spring assembly and install the new one after popping the new spring into place in the new extractor.

Average OEM extractor springs should be replaced beginning at 2,500 rounds and no later than 5,000. Better extractor springs will not require such frequent replacement with any ammunition – the Colt “Gold” extractor springs used in each rifle starting at 5,000 rounds were still providing reliable extraction at the 10,000 round mark, and would not have required replacement after 5,000 rounds.

Which Ammo To Buy

If Federal Brass Cased Ammo Performed So Great, Why Bother Buying Steel Cased Ammo?

The performance of the carbine firing Federal ammunition in this test was undoubtedly impressive. The firing of approximately 412 pounds of ammunition with very minimal maintenance in austere conditions without a single malfunction – not to mention remaining serviceable and combat accurate from the first shot to the last – could hardly be improved upon. To many who read this report, this is all the justification they need to purchase this type of ammo.

A man firing an AR-15 with Federal ammunition.
It is hard to argue with a functionally flawless performance.
To others, the increased cost of brass cased ammunition isn’t worth it – after all, the Wolf and Brown Bear ammo had very few malfunctions, all things considered. Plus, let’s be honest – in all likelihood, most people will never shoot 10,000 rounds through their AR-15. As a company we would be excited if they did, but the use these rifles saw was far beyond what is likely to be encountered in the real world. So, for many consumers, this test will be justification that buying steel cased ammunition is a sensible decision. In many cases, it is.

A photo showing two men firing steel ammunition.
Imported steel cased ammunition is a lot better than it is sometimes given credit for, especially considering the reduced price.

Although ammunition prices are volatile, the prices of brass and steel remain similar to one another – that is, brass is generally more expensive. We created a chart comparing the cost over time of each type, including ammunition and spare parts replacement costs.

The difference in price between brass and steel cased (more specifically, copper jacketed and bimetal jacketed) ammunition means that you’ll have plenty of savings with which to buy new barrels – even if you shoot so fast that you replace them every 4,000 rounds. For this chart, brass ammunition was calculated at $130 per thousand higher than steel and replacement barrels at $250 apiece.

A chart detailing the cost of shooting brass vs. steel ammunition over 10,000 rounds.The final decision is up to you, but now that you know some facts, you can make a better-informed decision.

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