Anthony Williams has written a fascinating account of his time spent shooting the Brugger & Thomet MP9 chambered in the diminutive 6.5x25mm CBJ round. The standard 6.5x25mm CBJ Ball1 round consists of a necked down 9x19mm NATO case with a 4mm (0.157″) tungsten bullet, weighing 30 grains, inside a 6.5mm plastic discarding sabot. Look what it does to armor …
One of the rounds biggest advantages is that is can be used in any 9mm NATO gun with nothing but a barrel change.
I highly recommend reading Tony’s article.
It is officially refeared to as a “Ball” round but this is a misnomer. Ball usually refers to a Full Metal Jacketed bullet, not a saboted non-jacketed bullet. ↩