Text & Photos by Jeff W. Zimba
Since the beginning of time, human beings have had an instinctual desire to create, and then to try and improve on their creations. Firearms and ammunition are notable examples of this quest. Early firearms were loaded with loose powder from a flask or container. The projectile was then loaded separately after the powder charge. This method was slow and tedious and eventually evolved into wrapping the powder and projectile in a paper “cartridge” to be loaded simultaneously; but this system still had no contained method of ignition.
Several designs combining all of the components of what we consider to be a modern cartridge were fielded with little success until the introduction of metallic cases. With the introduction of copper cases (and later brass) in the mid 1800s, several new cartridge loading and ignition techniques were introduced, including the Pinfire cartridge, the Rimfire cartridge and finally the Centerfire cartridge that we commonly use today. Not including shotgun shells, the brass cased, boxer primed cartridge is by far the most common ammunition type available and used today in the United States.
While there have been several experimental types of ammunition developed in the years since the turn of the 20th Century, none have really caught on in the commercial or mass produced military markets. One of the more interesting and radical ammunition designs includes the Gyrojet. The Gyrojet was a rifle and pistol designed by MBA in the late 1950s that fired a small rocket. They were most commonly manufactured in 12mm but were produced in smaller quantities in several other calibers as well. Many factors led to the end of the program without ever gaining a large following in the firearms market. Ammunition was costly to manufacture primarily due to the small quantities being produced and that ultimately hindered the popularity of the retail value of the firearms themselves. The Gyrojet rifles and pistols were documented in great detail in two previous issues of Small Arms Review (Vol. 5 No. 10 and Vol. 6 No. 4).
Another radical ammunition design to be experimented with on a large scale is Caseless ammunition. In this design, just as its name would suggest, there is no case. The propellant is formed into a “case” securing the projectile and the ignition system and is almost entirely utilized upon firing with a minimal amount of combustion material remaining. The best-known caseless ammunition program to date has been the German 4.7x21mm introduced during the 1978 NATO trials. It was an entry from the combined effort of H&K and Dynamit Nobel. It has been tested in several charge shape variations, weighing in from 3.4 to 5 grains. It has been tested as ball, tracer, plastic practice and blank ammo. This ammunition was designed for use in the experimental H&K G11 assault rifle and has never been adopted in a commercial or military capacity.
Fast forward to the 1990s. NATEC Ammunition (then Armtech, Inc.) CEO, Dr. Nabil Husseini, set out to establish the effectiveness of a high pressure, polymer-cased ammunition. Enlisting the services of DuPont, a world leader in manufacturing polymers, Dr. Husseini initiated the advances to engineer a polymer that would withstand the high pressures and temperatures associated with rifle ammunition. The result is NATEC’s PCA-Spectrum ammunition.
PCA (Polymer-Cased Ammunition) from NATEC is currently available in .223 Rem. and .308 Win. with several other calibers to follow, including .50 BMG. These new cartridges utilize standard projectiles, primers and propellants. The polymer cases are injection molded and the base is cold formed from brass. At the heart of the PCA ammunition is the unique manufacturing process that includes insert injection molding of the projectile into the polymer casing. No crimping is necessary and the cartridge is self-sealing to ensure this relationship is waterproof. After loading the propellant through the open base, the primed brass base cap is attached using an interference fit.
The Polymer Cased Ammo appears to have a few advantages over traditional brass cased cartridges. The most notable difference is a significant weight reduction in the loaded ammo. In comparing the weight of the PCA against a selection of traditional brass cased 55-grain ammo, a weight reduction of almost 34% was measured. Where the standard ammo averaged 39 rounds per pound, it takes 52 rounds of NATEC PCA to reach the same weight. To someone watching his gear in ounces, a 34% reduction in ammo weight may not be nearly as attractive as a 25% increase in ammo capacity with no additional weight burden.
Another attractive advantage of the PCA is that the cases are generally color coded to the ammo type. With this ammo it is immediately clear what kind of round is in your magazine or is loose to be loaded. The entire case being colored rather than a small portion on the tip of the projectile makes identification much easier and faster. The color codes are as follows:
• Red – 55gr. Tracer
• White – 55gr. & 62gr. FMJBT*
• Blue – 55gr. HPBT
• Green – 55gr. Sierra Blitz King
• Tan – 55gr. FMJ
• Black – 69gr. Sierra Match King
• Grey – 55gr. PSP
(*The White casings also indicate military grade ammunition.)
The transfer of heat is important in several aspects of shooting. Most noticeable at the range when using traditional brass cased ammunition is the heat transferred from a newly spent casing to the skin of the shooter. That is no longer a concern with NATEC PCA. Due to the unique insulating capabilities of this special polymer, the ejected cases are only lukewarm. No more burns resulting from the shooter to your left dropping a hot “brass rainbow” on your back when you are not expecting it. This “polymer rainbow” not only looks much more colorful but is more courteous to the other shooters.
The greatest advantage regarding heat is when discussing heat transfer in relation to the chamber area. In closed bolt systems, a chamber that is too hot can cause a cook-off with traditional brass cased ammunition that is left in the chamber. The excessive ambient heat causes the powder or primer to ignite creating a dangerous situation resulting from an unintended discharge. Primarily due to the insulating properties of the special polymer casing, less heat is transferred to the chamber than with traditional brass cased ammunition. This translates into a much better RBC (Rounds Before Cook-off) for all systems using these cases. Typical of the M16 system is an RBC of 180 rounds. Using the PCA ammunition allows for a greater sustained rate of fire.
A residual function of the PCA is that it retains shape during firing and is not formed to the chamber creating the tight fit typical of metal casings. This greatly reduces friction and eases extraction without adding to chamber wear and accelerating normal temperature gains. According to the manufacturer, the US Army has tested this ammunition in chamber temperatures of over 400 degrees without the typical ill effects. While the casing did start to lose rigidity over long periods of time at these high temperatures, it did not typically cook off or disconnect from the brass base cap and was allowed to eject normally.
At the opposite end of the temperature spectrum, SAR tested the ammunition in a cold weather environment. With the temperature below the freezing mark during all of our range time, cold weather failures would become very obvious. The ammunition was tested in four different firearms; an M16, a STAG-15L, a Ruger Mini-14 and a Robinson Armament M96 Expeditionary Rifle. The first test was a basic function test. It fed and fired in all test guns without malfunction of any kind. Several 55-grain brass cased rounds were fired in each firearm immediately followed by an equal number of NATEC rounds. The ejection distance was noticeably shorter in each firearm with the NATEC ammunition, as was the recoil impulse. When magazines were loaded with both types of ammunition it was immediately obvious to the shooter when the change took place.
After function testing was complete, several groups were fired with each rifle, with both types of ammo at 50 yards and 100 yards with open sights. All groups were similar in size and all were within the critical areas of a standard B27 silhouette target. The point of impact was the same with both types of ammo.
Using a PACT MKIV Timer and Chronograph, muzzle velocity was measured from each firearm. The 55-grain NATEC ammo averaged a speed 2,927 feet per second (fps) from a 16-inch barrel and 2,574 fps from an 11.5-inch barrel. The brass-cased ammo used for comparison was Norinco 55-grain FMJ and averaged 3,105 fps from a 16-inch barrel and 2,709 fps from an 11.5-inch barrel. Both types of ammo were extremely close in consistency. The NATEC ammo averaged 47 fps variance from high to low and the Norinco averaged 51 fps in variance.
A common question asked about Polymer Cased Ammunition from within our shooting community is, “Does it run in full auto?” At the end of the initial testing, two 20-round magazines were loaded with PCA ammo and the M16 with the 11.5-inch barrel was chosen for a full auto test. For the first magazine, the selector was first set to “semi” and two rounds were fired. The selector was then placed on “full” and the magazine was emptied in 3 to 4-round bursts. No problems were encountered. The second magazine was then inserted and emptied in a continuous 20-round burst. Again, no malfunctions occurred.
The M16 fired noticeably slower with the PCA ammo so the PACT MKIV Timer and Chronograph was used again, this time to measure rate of fire. Several strings with both types of ammo were recorded. Each string was measured by shooting a continuous 20-round burst. With a factory buffer, the Norinco ammo averaged 1,001 rounds per minute (rpm) and the NATEC PCA averaged 877 rpm with an average difference of 124 rpm. Again, as previously noted while firing the ammo in semiautomatic, the PCA empty cartridges were ejected almost one half the distance of that of the brass cased ammo and the felt recoil was noticeably less.
After recording these initial results, both types of ammo were tested again using an MGI Rate Reducing Buffer. In this round of testing, the Norinco ammo averaged 776 rpm and the NATEC ammo averaged 733 rpm. The interesting thing I have found with the MGI Rate Reducing Buffer is that it varies in rate reduction depending on the initial rate of fire; never allowing a drop below a certain point to affect reliability. While the decrease in rate of fire on the Norinco ammo averaged an incredible 225 rpm, the reduction with the NATEC ammo, which was initially considerably slower, was only 144 rpm. The initial rate of fire that was once separated by 124 rpm only averaged a difference of 43 rpm with the felt recoil and muzzle rise greatly reduced with both. No malfunctions of any kind were recorded while shooting in full auto, regardless of length of burst.While there were no failures to feed or extract during this testing, it was noted that after sitting in sub-freezing temperatures for several hours, the Robinson M96 started to experience failure to eject problems with the NATEC ammo. It is suspected that the culprit was the heavy lubricant previously used in the M96 and, due to the extreme cold weather, the action was operating much slower than usual and that, combined with the lighter residual energy in the ammo, prevented it from operating correctly.
No Fluted Chambers!
NATEC PCA has a warning NOT to use their ammunition in any fluted chamber. This is not a frivolous warning. It has meaning and should be strictly adhered to. But we did not know why or what would happen if we do. It was assumed that it would cause extraction problems. A decision was made, for the greater good of this article and the curiosity of everyone who ever wondered, to try it in a fluted chambered gun to see exactly what the problem would be. A Vector Arms V53 was chosen as the test weapon and a round was loaded into it and fired. Big mistake! The bolt came back and the brass base cap was seen flying through the air. Upon inspection, a beautifully fire-formed and now deeply fluted, baseless, polymer case could be seen in the chamber. On initial thought, it was nothing a broken shell extractor shouldn’t be able to remedy. But that was not the end of the story. The case, badly mangled, was finally removed and the chamber was cleaned thoroughly. The barrel was inspected, a fresh magazine of standard brass cased 5.56x45mm FMJ ammo inserted and the bolt was slammed home. Ca-chunk. The round stopped short and the bolt was far from battery. There was something in the chamber we could not see that was preventing the round from seating. The chamber needed to be cast several times with Cerrosafe, a metal with a low melting temperature that is frequently used for chamber castings by gunsmiths. Each casting would retrieve a little of the polymer that had become embedded into the flutes and eventually all was removed. Please learn from this hands-on, goofball testing method and relay it to all your friends when they ask, “What does it do if you fire it in a fluted chamber?” Now you know – heed the warning!
The ammo ran perfectly in every normal circumstance it was tested in and performed even in sub freezing temperatures. It performed well in both semiautomatic and full automatic modes of fire. The groups were almost identical when compared to traditional brass-cased ammo of the same weight. The lighter overall weight of the loaded ammo is a huge advantage in the opinion of the author, and has the potential to provide more safety to our men and women in uniform if accepted by the US Military. (Testing is currently underway.) The color-coded polymer casings make round identification fast and easy under any conditions. The manufacturer’s claims about the casings not being hot when ejected were right on the money as well. They could be immediately picked up without fear of being burned and they were barely warm at best.
There is also a “cool factor” that will be recognized by many recreational shooters and that has to count for something. The reaction from people not familiar with it is always one of curiosity and amazement. I’ll keep shooting it and keep watching the surprised faces of the shooters next to me picking up “brass” and wondering out loud what they just stumbled across. At an attractive price with an increasing availability, I think NATEC Polymer Cased Ammo will soon be showing up on firing lines nation wide. After more testing, readers can expect to see more information from the military community as well.
Polymer Cased Ammo
11 Arkansas Street
Plattsburgh, NY 12903
Ph: (518) 324-5625
Fax: (518) 324-5627
Rate Reducing M16 Buffers
102 Cottage Street
Bangor, Maine 04401
Ph: (207) 945-5441
P.O. Box 535025
Grand Prairie, TX 75053
Ph: (800) 722-8462
|This article first appeared in Small Arms Review V9N6 (March 2006)|