With full power ammo, they are about the same as 7.62x39mm power. It makes a good lower-rcoil round in a bolt gun, or subsonic is the best choice. In an AR - it is the best way to shoot 30 caliber bullets as AK ammo has various issues.

Both 300-221, but Whisper(R) is proprietary and 300 AAC BLACKOUT is a SAAMI standard. Remington and a lot of other companies make 300 BLK ammo now. There are over 70 companies supporting it, and 30 different gun makers.

http://www.saami.org/PubResources/CC...20Blackout.pdf

Spend a day reading here - tons of info:

http://www.300blktalk.com/forum/

* AAC - uppers, rifles, silencers, and ammunition.
* Adams Arms - rifles and uppers.
* All Weather Arms - brass processing.
* AR-Stoner - barrels.
* Atlanta Arms - ammo.
* Barnes Bullets - ammo, bullets.
* BFG Cartridges - Savage barrels.
* Black Hole Weaponry - barrels.
* Brad's Warehouse - converted brass.
* Bushmaster Firearms - uppers and rifles.
* BWE Firearms - rifles, uppers, and suppressors.
* CMMG - barrels, uppers, and ammo.
* Compass Lake Engineering - AR barrels.
* Cor-Bon - ammo
* Core15 - rifles, uppers.
* Delta Company Arms - rifles, barrels, uppers.
* Dillon Precision - reloading conversion kits.
* Double Tap - ammo.
* DPMS - rifles and uppers.
* DS Arms - rifles and uppers.
* Forster - reloading dies.
* Grim Reaper Tactical - barrels and uppers.
* Gunn - ammo.
* Hornady - ammo, dies, brass.
* Kel-Tec - SU16C.
* Kiss Tactical - lowers.
* Lee - reloading dies.
* L.E. Wilson - case gauges.
* Lewis Machine and Tool - barrels, uppers, rifles.
* Loki Weapon Systems - uppers/rifles.
* Lone Star Armory - 300 AAC BLACKOUT marked lowers.
* Lothar Walther - barrels.
* LWRCI - rifles.
* Match Grade Machine - Thompson barrels.
* McGowen Barrel - Savage and other barrels.
* McCourt Munitions - ammo.
* Model 1 Sales - AR barrels/uppers
* Montana Rifleman - barrels.
* Noveske - rifles and uppers.
* Olympic Arms - rifles and uppers.
* One Shot - ammo.
* Pac-Nor - barrels.
* Pacific Tool and Gauge - reamers and gauges.
* PalmettoStateArmory - uppers.
* PNW Arms - ammo.
* Primary Weapons Systems - rifles and uppers.
* Rainer Arms - barrels.
* Raven Armament Company - ammo and uppers.
* Redding - dies.
* Remington - ammunition.
* Right 2 Bear Ammo - ammunition.
* Robarms - XCR Micro rifle.
* Ron Williams - barrels.
* RUAG - ammo.
* Satern Custom Machining, Inc. - barrels.
* Savage - rifles.
* Selph Arms LLC - barrels, uppers, re-chambering, and rifles.
* SI Defense - barrels.
* Sig Sauer - rifles.
* Smith & Wesson - rifles, uppers.
* Sierra - bullets.
* SilencerCo - silencers.
* Southern Ballistic Research - ammo.
* Southwest Ammunition, LLC - ammo.
* Spike's Tactical - uppers and rifles.
* Summit - ammo.
* Surefire - 300 BLK sound suppressor.
* The Bullet Works - bullets and ammunition.
* Triton Arms - AR barrels.
* Ultra Tech - ammo (Australia)
* Umlaut Industries - 300 BLK caliber marked Rifles, Upper and Lowers. 16" and 10" Factory Title II.
* White Oak Precision - AR barrels.
* Wilson Combat - rifles, hunting and self defense ammunition.