Joe B’s Bullet Construction Test
First, I ran the outliers over my GemPro 250 electronic scale that weights in units of 0.01 grains. Lightest was 54.92 grains and the heaviest was 55.90 grains. There was one at 55.61 grains that I culled from the group. From the mid-weights I sorted out five that were exactly 55.50 grains.
Visual inspection followed under a 4X glass. The easiest to see was that the lead core was not positioned the same. While on the outliers, they were from 0.030” below the base of the jacket, to flush with the base. The middies were from 0.030” to 0.005” below, measurements done with a depth micrometer. Next the bullets were inserted point first into an orifice 0.125” in a steel plate, and height measure of how much stuck up above the hole. The bullets with the most lead exposed on the boattail, also had the largest diameter ogive, and i.e. stuck up the least amount from the plate.
Using a micrometer with a 0.0001”, one ten thousandth scale, lengths were measured and all bullets were within 0.010”. Bullets were then measured above the cannelures and again below but above the beginning of the boattail. All bullets, even those with expanded ogive, were remarkably even at .2229” all around the bullets. However below the cannelure the bullets with lead all with way to the base of the jacket varied from .2229” to .2232” at random points around the circumference. Bullets with the lead at least 0.020” below the base of the jacket were .2229” below the cannelure.
Using a radius gauge, the base inside the boattail was measured. Bullets that had lead all the way to the base had inconsistent radii at least at one point around the circumference. Bullets with deep seated cores had even radii. The angle of the boattail also varied as the more lead exposed bullets had about a seventy degree included angle while the deep seated cores were an even sixty degrees included angle.
From the above observations, my hypothesis is that since the mass, weight, is the same, the cores of some bullets are seated to the rear of the jacket, therefore there must be voids in the front of the bullet.
This lead to sectioning 10 bullets: 5 from the middle of the population and 5 outliers. Bullets were milled to about 55% of bullet diameter. Jacket thickness at the ogive varied from 0.032” to 0.039” and point thickness was 0.065”. I was unable to determine if all jackets varied in thickness as the bullets were not strong enough to allow another 90 degree cut taken. However 6 of the jackets showed variations.
My hypothesis was in error, as there were no voids. What there was is a soft waxy material between the jacket and the core, soluble in alcohol. Researching how jackets are drawn from gilding metal discs, it appears to be from lubing the blanks as they are stamped out over several drawing processes. This wax was not evenly distributed around the cores but in one spot stretched out along the center line. Bullets with deep seated cores had no evidence of wax, the farther the core set back the more wax was in between the jacket and the core. I tried to dissolve the wax and then evaporate the alcohol, but the quantity was so small I did not have the apparatus to weigh or measure it.
None of my equipment could spin the bullets faster than 3600 rpm and at that speed I could detect nor measure any vibration or wobble. Rolling the bullets down a sheet of plate glass with a 0.20 feeler gauge under one side did produce an interesting effect. Bullets with deep seated cores and equal diameters above and below the cannelure would roll straight off the bottom of the glass. Bullets with lead to the bottom of the boattail would take a path towards the nose of the bullet until the bullet was perpendicular to the original path. I don’t know if that is because those had a slightly larger diameter below the cannelure or because they were heavier towards the base or because they were not balanced.
Bullets from the sample of 40 grain plastic tipped bullets were boring. The weight variations were 0.06 grains! Jacket thickness was 0.012” the same as a 22 LR case and even on the five cases dissected. None of my equipment or tests could discern any difference between bullets.
In summery my hypothesis is that:
1: weighting is futile
2: core placement in the jacket varies
3: because of manufacture, center of mass varies from center of form from back to front and around the axis of the bullet
4: sorting should be by how deep the lead core finishes up inside the jacket
I have many more pictures if interested.