Taylor, this Adaptive Combat Rifle is actually chambered in 6.8mm Remington SPC.

it is chambered in 6.8mm Remington SPC II SEE ******* The Bushmaster ACR or Adaptive Combat Rifle features an adjustable gas piston system which runs cleaner and better than it's direct gas impingement counterparts. The ACR is a modular system which allows you to swap out barrels, stocks, and even hand guards. This particular version comes standard with a polymer hand guard and a folding/seven position telescoping stock. Additional it features a 16.5" cold hammer forged barrel along with ambidextrous controls that even a southpaw shooter would enjoy. Specifications and Features: Bushmaster ACR Basic Semi Auto Rifle 90955 Adaptive Combat Rifle Adjustable Gas Piston System ********6.8mm Remington SPC II 16.5" Cold Hammer Forged Barrel 30 Round Magazine Accepts standard pattern AR-15 magazines Folding/Seven Position Telescoping High Impact Polymer Stock Rubber Buttpad Polymer Hand Guard AAC 51T Flash Hider Ambidextrous Safety, Bolt Lock, and Magazine Catch Reversible Non-Reciprocating Charging Handle Proprietary Modular Receiver Matte Black Finish

it is chambered in 6.8mm Remington SPC II SEE ******* The Bushmaster ACR or Adaptive Combat Rifle features an adjustable gas piston system which runs cleaner and better than it's direct gas impingement counterparts. The ACR is a modular system which allows you to swap out barrels, stocks, and even hand guards. This particular version comes standard with a polymer hand guard and a folding/seven position telescoping stock. Additional it features a 16.5" cold hammer forged barrel along with ambidextrous controls that even a southpaw shooter would enjoy.
Specifications and Features:
Bushmaster ACR Basic Semi Auto Rifle 90955
Adaptive Combat Rifle
Adjustable Gas Piston System
********6.8mm Remington SPC II
16.5" Cold Hammer Forged Barrel
30 Round Magazine
Accepts standard pattern AR-15 magazines
Folding/Seven Position Telescoping High Impact Polymer Stock
Rubber Buttpad
Polymer Hand Guard
AAC 51T Flash Hider
Ambidextrous Safety, Bolt Lock, and Magazine Catch
Reversible Non-Reciprocating Charging Handle
Proprietary Modular Receiver
Matte Black Finish