From Marvel Comics The Punisher Armory No 1

Colt XM177EI:

“One good idea deserves another … on my strip down blotter is a Vietnam-era Colt XM177EI. It was an experimental improvement of the CAR-15 (Colt Auto Rifle-15″ (barrel)), and really helped that gun’s excessive recoil and muzzle blast.

So, my Commando is good, but then they upgraded the specs of the barrel of the standard M16A2 (of the Marine Corps) and called it AR-15 HBAR (Heavy Barreled Assault Rifle) in 5.56 mm.

Shots cooler and more accurately … but I could think of some improvements, too. Like an M203 40 mm grenade launcher and an Aimlight PIN66XL entry light.”

Published by Marvel Comics in The Punisher Armory No. 1, July, 1990