The Science of Sorting Things Out: Ammunition Edition
Desperate times lead to desperate measurements. There is a nationwide ammunition shortage in the USA. Regardless of the reason for it, we are doing what we can to continue practicing, which means, in my case, sorting a box of several hundred bullets to reload .223 Remington cartridges.
A friend of a friend has fallen on hard times, and his shooting supplies were for sale. Several boxes of moly-coated .223 bullets of various weights were unsealed in a larger box. They came open. The result was a mixed moly mess. I was the only person willing to do the sorting. I got them cheap.
How hard can it be, right? All the bullets are the same caliber & diameter (.224), so only the LENGTH should change for the various weights. Since I wasn't sure how many different types were present, I started weighing them, and measuring lengths with a vernier.
So far I have found 4 distinct weights: 53, 68, 75 and 77 grains. I recorded the lengths I found, then started sorting into boxes of each weight, based on the measured length. Ha! After sorting over a hundred this way, I realized that some of the lengths varied a couple thousandths (0.002") more than I was expecting.
"That's interesting" - science words meaning "you're about to learn something".
I started weighing EACH bullet after measuring. Sure enough, there were 77 grain bullets in the length range I had recorded for 68 grain bullets. Evidently, the ogive, or shape of the curve of the bullet nose, can distribute mass differently enough to make one 0.980" bullet weigh 9 grains more than another of the same length.
"Who cares?" you might ask. "Won't that affect accuracy just a little bit?". Well I get nervous about such things. As I understand the physics of internal ballistics, the heavier the bullet, the higher the chamber pressure in the rifle, given the same charge of gun powder. If I load a 77 grain bullet over a charge intended for 68, "Bad Things Can Happen". (primer flattening, case damage, possibly case rupture, and subjecting an expensive competition rifle to repeated excessive chamber pressure).
Penalty for erroneous assumption? All the sorted boxes got poured back into the big box. Except the 53's, they're eyeball obvious.
So I started over, weighing EVERY bullet. After about a hundred, I was pretty certain that there weren't any other weights mixed in, and settled on one shortcut to speed things up: rather than sliding the weights on my powder scale/beam balance to individually weigh each bullet, I set it for 76 grains. The pointer balances high for 77, low for 75, and rests on the bottom for 68 grain bullets. The 53's, bless them, are obvious enough to the eye, and I don't reload that weight anyway.
By the time I finish sorting, even minimum wage would probably put me over the retail value of the bullets. It's a good thing I was looking for an excuse to hang out in my nice cool man-cave.
A friend of a friend has fallen on hard times, and his shooting supplies were for sale. Several boxes of moly-coated .223 bullets of various weights were unsealed in a larger box. They came open. The result was a mixed moly mess. I was the only person willing to do the sorting. I got them cheap.
How hard can it be, right? All the bullets are the same caliber & diameter (.224), so only the LENGTH should change for the various weights. Since I wasn't sure how many different types were present, I started weighing them, and measuring lengths with a vernier.
So far I have found 4 distinct weights: 53, 68, 75 and 77 grains. I recorded the lengths I found, then started sorting into boxes of each weight, based on the measured length. Ha! After sorting over a hundred this way, I realized that some of the lengths varied a couple thousandths (0.002") more than I was expecting.
"That's interesting" - science words meaning "you're about to learn something".
I started weighing EACH bullet after measuring. Sure enough, there were 77 grain bullets in the length range I had recorded for 68 grain bullets. Evidently, the ogive, or shape of the curve of the bullet nose, can distribute mass differently enough to make one 0.980" bullet weigh 9 grains more than another of the same length.
"Who cares?" you might ask. "Won't that affect accuracy just a little bit?". Well I get nervous about such things. As I understand the physics of internal ballistics, the heavier the bullet, the higher the chamber pressure in the rifle, given the same charge of gun powder. If I load a 77 grain bullet over a charge intended for 68, "Bad Things Can Happen". (primer flattening, case damage, possibly case rupture, and subjecting an expensive competition rifle to repeated excessive chamber pressure).
Penalty for erroneous assumption? All the sorted boxes got poured back into the big box. Except the 53's, they're eyeball obvious.
So I started over, weighing EVERY bullet. After about a hundred, I was pretty certain that there weren't any other weights mixed in, and settled on one shortcut to speed things up: rather than sliding the weights on my powder scale/beam balance to individually weigh each bullet, I set it for 76 grains. The pointer balances high for 77, low for 75, and rests on the bottom for 68 grain bullets. The 53's, bless them, are obvious enough to the eye, and I don't reload that weight anyway.
By the time I finish sorting, even minimum wage would probably put me over the retail value of the bullets. It's a good thing I was looking for an excuse to hang out in my nice cool man-cave.