Also designed by Tom Burczynski (of Hydrashok fame), the EFMJ is one of the latest advancements in expanding bullet design since the JHP.

It features a fully jacketed bullet but has a foam or rubber insert in the front which is crushed upon impact. The crushing force makes the bullet expand and provide controlled penetration, this also aids in better energy transfer.

The major advantage of this is that it lets you use a bullet that has a ball profile and thus ensure feeding reliability but still have an expanding projectile. Big gaping wounds make for fast incapacitation.

One might also suggest that this is a solution looking for a problem, as this has been known to happen in the world of guns. We got calibers for shooting ants to T. Rex. The EFMJ in fact works very similarly to a Jacketed Soft Point and afaik there is no real need for it. Just another way to do the same thing, well I suppose TIMTOWTDI.