Eley's goal behind the initial TenEx development was to provide British-made .22 LR ammunition, built to extreme consistency, that British shooters could use to win British shooting competitions. (American-made Western Supermatch and Winchester EZXS were the dominant competition loads of the time.) It worked. The 1951 British Championship and the Grand Aggregate events at Bisley were won by Eley team shooters using TenEx.
It was the first time these titles were won using British-made ammunition. Eley spent the following decade readying TenEx to compete in the international market, steadily improving the quality by means of a "half tolerance" standard for TenEx components compared to standard ammunition and the creation in 1962 of a segregated TenEx component manufacturing and cartridge assembly facility where half tolerance became the standard tolerance. Those wins at the 1964 Olympics and in the following years were the proof of their success.
Then came the breakthrough Eley executives view as the most important single factor in the TenEx story: Eleyprime. During the years that the engineers worked on perfecting Eley ammunition, they were also engaged in ongoing research into priming technology. Commonly used priming material is percussive; bump it, it goes bang; give it a spark, it goes bang; look at it cross-eyed, it goes bang. In the 1960s and 1970s ammunition manufacturers worldwide used essentially the same technology.
Concerned by the inevitability of explosive accidents no matter the precautions taken, Eley in 1975 embarked on a project to find a new priming process. In 1979 chemists working on a dry powder mixture for filling .22 cases discovered that it was non-explosive until exposed to water, whereupon a chemic
A closely guarded (and patented) secret, this new Eleyprime process had two huge consequences: It eliminated the risk of explosion from the preparation and dispensing of priming compounds, and it allowed the amount of priming material applied to each individual rimfire case to be very tightly controlled in a normal workshop environment using automatic equipment.
This last part is critical because it has long been known that case-to-case variation in the amount of priming material is the most important factor regarding variations in .22 LR rimfire performance. This is due to the fact that in small rimfire cartridges the primer is a significant portion of the actual propelling charge (much more so than in larger centerfire cartridges) and because conventional priming compound is too sensitive to be aggressively metered and applied.
al reaction converted it to conventional lead styphnate (primer compound).
The Eleyprime System allows exactly identical amounts of the inert powder to be put in each case. Then a round-tip rod is inserted down into the case to press the powder evenly into, and around, the rim, and a single, metered drop of water is added, which activates the compound over a several-hour period.
After drying, the cases can then be conventionally charged with precisely metered propellant (five rounds at a time on the TenEx loaders). Before Eleyprime, there was an average 31 to 39 milligram spread in the amount of priming material round-to-round in TenEx ammunition. With the Eleyprime System (EPS), the spread was reduced to only plus/minus 1.0 milligram. It was a stunning achievement, and in 1988 Eley received the prestigious Queen's Award for Technological Achievement.
But technology does not stand still. TenEx maintained its preeminent place among premium .22 LR ammunition during the 1980s and 1990s, but other ammunitionmakers advanced their own manufacturing techniques. Eley monitored their rivals' progress, and in its own lab and testing ranges regularly compared the competitors' performance against TenEx.
The performance standard Eley applied was 10-shot test groups, fired from a fixtured rifle (not a special test barrel) at 50 meters. The specification called for a nominal percentage of test groups to measure less than 15 millimeters (the diameter of the 10-ring on a standard 50-meter smallbore rifle target). As of 1998, TenEx performance ran 8 to 10 percent; that is, 8 to 10 percent of all 10-shot groups fired were less than 15mm diameter. It was the best in the world, but new loads from Lapua and Federal Cartridge's new match ammunition were knocking on the door.
Eley tasked its engineers to take a blank sheet of paper, start with the Eleyprime system as the only foundation, and reinvent the TenEx cartridge from the ground up. The goal was to improve TenEx performance to at least a 30-percent 15mm-group standard; in other words, make it three times better. 'm not allowed to tell you how they did everything they did, but even in summary it's one of the most impressive achievements I've seen in my 30 years in this business. Eley engineers identified 50 primary variables--basics like bullet mass, case internal volume, and proThen they determined 200 secondary variables--things like the ambient humidity in the assembly facility, the metallurgy of the cases, human competence. Finally, they identified 700 tertiary variables--subtle things the TenEx project manager told me turned out to be the ultimate keys to getting things really up to "the TenEx level." For example: weather conditions in the country where the propellant powder is manufactured on the day that particular lot of powder was mixed. (Yes, Eley actually adjusts the TenEx loading profile for each powder lot based on this and other equally subtle considerations. The same is true of the other end of the process; manufacturing "lots" of TenEx consist of one day's run from a single loading machine because the weather is different each day.)
With nearly 1000 variables charted, the engineers addressed bullet and case design. Bullet design was analyzed with sophisticated computer modelling for in-flight characteristics. They discovered that a flatnose projectile was distinctly better for subsonic velocities out to 50 meters. The reason is that bullet stability is enhanced the more forward the center of pressure (air-pressure resistance) is located forward of the center of gravity of the bullet, and roundnose bullets do not "push" the center of pressure as far forward. (Incidentally, the small "pip" visible in the center of current TenEx bullets is not a ballistic feature; it's the result of an air pocket in the mold that allows the sharp-cornered edges of the nose to form fully.)
They also determined that the presence of lead oxide in a bullet was a primary cause of "detached shots" (what non-engineers call "flyers") because of differential resistance to passage through the bore. So TenEx bullet material is fabricated in an oxygen-free atmosphere and lubed with a soft tallow/beeswax material, the same lube Eley used 150 years ago; most modern bullet lubes are paraffin-based, which is harder.
I was particularly intrigued by the information that the engineers had determined the base of a bullet was much more significant for accuracy than the nose of the bullet. In-flight tests showed that a very slight mar, burr, or scratch on the bullet heel would almost always result in significant yaw angle upon departure from the muzzle. They could actually pinch the nose of the bullet with a pair of pliers and it would have a much lesser effect on point of impact. Consequently, the heel of every TenEx bullet is visually inspected by computer before loading, and bullets with even the slightest imperfection are discarded.
Yeah, it's all advertising nonsense. Eutectic and Larry win again.