120 vs 123

[Stugotz]

123gr comes from European metric system since 8 grams = 123 grains.

5 grams = 77gr
7 grams = 108gr
8 grams = 123gr
9 grams is 139gr
10 grams = 155gr
10.1 grams = 156gr
11 grams = 170gr
12 grams = 185gr
13 grams = 200gr

You will notice 139gr and 156gr a lot with early 1900 century ammunition from Europe for 6.5x55 Mauser. In the US bullet market, you typically see even numbers in grains with several exceptions.

87gr came from the .250 Savage and marketing to where they could break the 3000fps barrier for a factory load. Testing demonstrated that in order to get consistent 3000fps performance at factory loadings, the 90gr bullet wouldn’t achieve those regularly enough, so they dropped the projectile weight down to 87gr and facilitated the .250-3000 moniker.

You see some carry-over of the gram-based weights in 6.5mm and 7mm in the US, especially with 139gr.

I was always curious about the odd numbers...