20mm x 102


Please, help me to identify these 20mmx102 :

Left : inert (M51 ?) but, why these colors (fake, …)
Center : M55A2 (FNB), That means the red tip ?
Right : The length of the case (20mmx102 !) is 104.1 mm. Why ?




I cannot answer your questions, but I can say that the only 20x102mm fired case in my collection also measures 104mm. Hmmmm… Mine is a comon and typical US made brass case.



Mine also measures 104mm. Look how deep the crimp is on the crimped rounds shown. That would easily add 2mm to the neck length when the neck is straightened after firing. 102mm looks to be the measurement before firing.


Ok for the third, thanks. No idea for the first two ?