The Whisper cartridge is a lightweight, hyper velocity design using an aluminum core and pre-stressed jacket. The aluminum core initiates the expansion slightly after contact, pressing back into the pre-stressed jacket and activating a violent, incapacitating energy transfer. The cartridge is ideal for close fire contacts of unarmored and/or lightly armored targets. Not to be mistaken for .300 Blackout, since Whisper was developed almost 20 years before it.