Most projectiles exhibited BC’s relatively close to published values for 150 to 200 yards of flight. Beyond these distances they all showed BC’s substantially below published values [because the tips were melting].
"Drag increases stopped at velocities below approximately 2,100 fps. This behavior was not observed with hollow point or exposed lead (spitzer) style designs. The problem magnified as the velocity was increased.
The tip of a bullet at 3,000 fps will see temperatures as high as 850 degrees F .... These temperatures on the tip were a known fact. What wasn’t known was how long it would take ... for the polymer tips to begin showing effects, if at all. As it turns out it is within the first 100 yards of flight. Currently used polymers in projectile tips begin to have properties like rubber at approximately -65 to 50 degrees F and will melt at 300 to 350 degrees F, depending on the exact polymer.
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