8mm Lebel Balle D question


#1

The French 8mm Balle D of 1898 was a remarkable military bullet, being solid brass and the first one in service to have both a sharply pointed bullet and a boat tail. Drawings indicate that it looks very modern even by today’s standards.

Does anyone know the Form Factor and/or Ballistic Coefficient for this bullet, preferably G7 although G1 would do?

Thanks for any help.


#2

The problem is that the published official data (supersonic velocity figures in French MG firing table from 1932) neither fit G1 nor G7 well.
One can compute a form factor i1=0.460 and i7=0.892 (based on 8.3 mm diameter and 12.8 g) but the drag curve from the velocity figures does not fit these models well (2.1 and 5.5 percent standard deviation).

The data fits the drag curve of Mayevski-Sabudski best (in other words: Ingall’s tables; iI=0.465, 1.1 percent stddev). Same applies for Siacci. But these are obviously not models one would associate with the slender shape of balle D.

Jean Huon prints other velocity figures in his French book on bolt operated rifles. But these are in my view even more suspectible (constant CD fits best!).

So if someone could bring up other data from reliable sources, that turn out to be in agreement with the balle D shape, it would be a big help not just for Tony.