April 1st, 2012

Powder Kernel Uniforming for Ultimate Long-Range Accuracy

MFR ScaleSuccessful long-range shooters know that careful weighing of powder charges helps them achieve superior long-range accuracy. By maintaining powder charges within very narrow weight tolerances, hand-loaders can produce ammo with more consistent muzzle velocities from shot to shot. Low Extreme Spread (ES) and Standard Deviation (SD) numbers translate directly to reduced vertical dispersion at very long ranges (although velocity is not the only contributing factor to vertical spread). In pursuit of load weight uniformity, many of our top long-range aces have invested in the latest, high-tech magnetic force restoration (MFR) digital scales (such as the Sartorius GD503). These laboratory-grade MFR scales are extremely stable (with minimal drift) and they can reliably measure to .005 grain, that is five thousandths of a grain. That is less than the weight of one kernel of typical extruded powder. For example, with Varget, there are three to four kernels in one-tenth of one grain of Varget. That means each kernel weighs .025 to .035 grains.

With the capability of modern modern MFR scales to measure less than one-hundreth of a grain, we have a new frontier in precision reloading. You’ll note, in the preceding paragraph, we said that one-tenth of one grain of Varget is three or four kernels. Well, “which is it?” you might ask. The answer is that it might be three, or it might be four, depending on the size of the individual kernels. That’s a disturbing uncertainty that we simply had to accept… until now.

Powder Kernel Uniforming — A Breakthrough
We now have the tools and the methodology to resolve the inherent uncertainty in individual kernel weight. Using the new technique of powder kernel uniforming, first pioneered by German Salazar, we can now, for the first time, ensure that every kernel of powder that goes into a cartridge is virtually the same weight — the same, in fact, within 0.01 grain (one-hundredth of a grain) TOTAL spread.

MFR ScaleFor a reloader looking to achieve “perfect” load weight uniformity, powder kernel uniforming offers the ultimate control over powder weight. The method we devised to uniform individual kernels consists of kernel core-drilling. The propellant we chose for this kernel-uniforming test was a new prototype (not yet commercially available) EuroChemie RL “X” propellant. This was chosen because it offered relatively large, can-shaped kernels that could be drilled relatively easily.

Powder Kernel Uniforming TestCore-Drilling Kernels with Micro Drill-Bits
The center of each kernel was bored out with a micro-drill. But here’s the key. Before drilling, we first weighed each kernel. Then we selected a micro drill bit of appropriate diameter to achieve uniform weights. With the heavier kernels (in the 0.04 gr range) we used a larger micro-bit. With the lighter kernels (in the 0.02 range), we selected a smaller diameter micro-bit that removed less material from the center of the kernel. Obviously, many kernels were ruined while we perfected the drilling process. It required great patience and a very steady hand. But after a few dozen hours of drilling, we had a batch of uniformed kernels that were all within plus or minus .005 grains (.01 grain ES). Now we were ready to do some testing.

Powder Kernel Uniforming Test

Powder Kernel Uniforming TestProof That It Works
All this time-consuming work to drill holes in individual kernels would be pointless, of course, if it did not produce meaningful accuracy gains. The proof, as they say, is “on the target”. We were curious to see if our uniformed powder kernels would out-perform unmodified kernels, so we did some field testing. We prepared two batches of 6mmBR ammo in Lapua brass, with full case prep, and bullet base to ogive sorting (we wanted to eliminate as many variables as possible). Bullets were Lapua 105gr Scenar Ls, which proved to be some of the most consistent projectiles we’ve ever measured.

One set of rounds was loaded with a carefully-weighed charge of unmodified kernels. Case to case charge weight was held to .05 grain (half a tenth uniformity). Then we prepared a second batch of cartridges with uniformed kernels, using the exact same charge weight, also held to .05 grain (half a tenth) tolerances. We took these rounds to the range, and did a “round-robin” test at 800 yards, shooting one of each type in sequence (i.e. one uniformed on right, then one non-uniformed on left) until we had two 10-round groups. The test was done with a rail gun fitted with a 1:8″ twist, 28″ Krieger 0.236″ land barrel. The uniformed-kernel ammo was shot at the right diamond, while the non-uniformed rounds were shot at the left diamond. Conditions were good, so we simply “held center” on every shot. No attempt was made to correct for wind as our primary concern was vertical dispersion.

Powder Kernel Uniforming Test

Ammo with Uniformed Kernels Shows Significantly Less Vertical Dispersion at Long Range
As you can see, the uniformed-kernel ammo out-performed the non-uniformed ammo. The difference is quite clear. The rounds with non-uniformed kernels (on the left) produced a 10-shot group with roughly 3.0 inches of vertical dispersion. On the right, our ammo with uniformed kernels produced a group with 9 of 10 shots showing roughly 1.75 inches of vertical dispersion (we did have one high flier among the uniformed-kernel rounds). Additionally, we had a lower 10-shot ES and SD with the uniformed-kernel ammo. We repeated this test two more times and the results were similar. The targets speak for themselves. If you are looking for ultimate long-range accuracy, powder kernel uniforming is a “new frontier” you may wish to explore. With all other factors held constant, we were able to reduce vertical dispersion by more than an inch at 800 yards by drill-uniforming our NitroChemie powder. That’s huge in the long-range game.

Yes, the kernel-uniforming process is incredibly time-consuming and tedious, and a set of micro-drills is not cheap. We also freely acknowledge that the process may be much less productive with narrow-kernel propellants that are hard to drill. (Also EuroChemie powders are preferred because the burn rate controlling compounds are impregnated throughout the entire kernel — not just the outside.) But the potential for significant accuracy gains is there. We proved that.

Is it worth the huge investment of time to drill your powder kernels? That’s a question each reader must ask himself. But if you know the competitor on the next bench over has uniformed his kernels, can you afford not to do the same? Sometimes the extra effort is worth it, just for the peace of mind you get knowing you’ve done everything possible to achieve “ultimate accuracy”.

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