Majority of the AR-15's in 5.56 have 16" barrels almost all under 20", yet most bolt guns in same caliber are 22". You lose more velocity per inch in a small caliber that a larger caliber.
My choices in larger bore rifle barrels...50 B&M Super Short 16"...458 B&M 18"... 460 S&W 18"...460 Bushmaster 16" & 20"...375 Ruger 20"
