Honest questions about bullet coating(s)

[Michael Courtney]

One question that I keep running over in my mind is the linearity that your test has shown. I have found during my testing little linearity...mostly an upward trend made up of a series of flatter nodes. I see none of that in your chart so I wonder if you took you speeds up closer to the 3000fps zone if other dynamics might enter the picture that might change your results.

Blue Dot performs much differently in 5.56 mm NATO than most rifle powders, being primarily designed for pistol and shotgun use and thus much faster than most rifle powders. We have also found that it is safe to use over a wide range of powder charges (4-14 grains with the bullets tested). Covering a wide range of muzzle energies (roughly 500-1000 ft lbs) and velocities (roughly 1900-2850 fps) is important to how the analytical method works to determine friction. Our friction testing is thus much different from much hobbyist testing where the reloader is focused on charges with 10-15% of the max load and a narrow range of muzzle velocities.

Being such a fast powder, 14 grains of Blue Dot produces nearly 50,000 psi with a 55 grain bullet and nearly 55,000 psi with a 62 grain bullet. Going up to 15 grains of powder would likely exceed SAAMI pressure limits in .223 Rem for both bullets. One might creep closer to 3000 fps by going up in 0.1 or 0.2 grain increments, but the experimental method is designed is to cover a wide range of muzzle energies with a few big steps in powder charge rather than a small range of muzzle velocity with many small steps.

As it happens, we do have data where we adjusted the charge of Blue Dot in small steps to meet different experimental goals (armor testing) that require smaller increments in muzzle velocity. The behavior of muzzle energy vs. powder charge still showed a very high degree of linearity, though we were careful not to exceed safe pressure levels.