Many users of 5.56 x 45 ammo are craving the M855 Green Tip, thinking it is a step closer to the ultimate. I've done some reading and head scratching on this. I have some first person experience -former Marine, one year in Vietnam. The wounds we inflicted on our adversaries were often gruesome. I grew up hunting and shooting and knew there was something almost mystical about the black Colt and its tiny round. I soon learned about "YAW", or tumble in layman terms. It's short- coming was range. New war in the middle east dictated a need for more range. M855 is developed with a non lead bullet and the range and accuracy needed to neutralize combatants with AK-47's taking pot shots. Problem solved. Hold on though. It's doesn't yaw (tumble) as readily. "We're making hits on the insurgents - sometime multiple hits without quick kills". They are dead, just not dead yet. That's what you're getting with the M855. It does have a the ability to penetrate steel and concrete - and body armor! Yuk says Obama. Can't have it! But, is that what you want when you hear that "bump -bang or crash at 2:00 am? The kids are asleep two sheet rock walls over and you grab your M4 with M855 ammo? I hope you know better. Your neighbors hope you know better. It has its place, but not in this situation. Remember what I said about "YAW". You don't need 600 -800 yard shots standing in the middle of your house. You don't need barrier penetration. You need terminal effects - tumble and fragmentation. That's what we had in Vietnam. It did its magic so well I wondered how the Geneva convention rules of war allowed it. In 2010 a new bullet was adopted that we will all crave, but will likely never have. Tad-Dah! The M855m1 EPR. (Enhanced performance round) this Bronze tip round has the non lead bullet with the hardened steel penetrator. Guess what - it tumbles. Yeh! Even at long range. The Physiology of the insurgents or ISIS plays a role in the failure if the M855. Usually thin, they have torsos of 7.5" thick. The M855 does not begin to yaw until 7" penetration, often exiting the body "ice-picking" you might say. The EPR requires less than 3" beyond impact point to begin to yaw and fragment leaving a 4-6" cavity, minimum penetration depth of 12", and doing it consistently. It can also penetrate 3/8" hardened steel at 350 meters( twice as far as M855 does). So, I don't think I need the M855 green tip ammo. If ATF says no-no-no I'm okay. If they continue to allow it I'm fine too. If they allow M855M1 EPR don't get in my way.