Keeping The Lead
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.

Eley rimfire cases are formed from specially alloyed sheets of copper by progressive individual stamping under extremely controlled conditions. Each Eley TenEx case is individually subject to close visual inspection.

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.

I'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 propellant charge mass.

Then 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.