Overseas major issues were found in Afghanistan especially at distance and in certain situations upclose that the round was not performing as designed and it wasn’t effective at dropping the taliban.
The round has had proven problems just zipping through targets and not tumbling as designed. Plenty of articles over the years talking about it and the army tried to correct its short comings with the M855a1 that with its high pressures was wearing guns out 50% faster. This has been a well known problem with the round especially out of 14.5 inch rifles we use. Certainly not pulling it out of my ass, and it has been a major issue for over two decades plus now. How is any of this news? The 9 years I spent as a grunt we had issues with it and friends who are still in were still not happy with the m855a1 revised round.
2002
https://defensereview.com/weaponammunition-problems-in-afghanistan-the-kalashnikov-solution/
2008
https://www.nbcnews.com/id/wbna24828356
2010
http://bulletin.accurateshooter.com/2010/06/u-s-army-issues-new-m855a1-ammo-to-troops-in-afghanistan/
2010
https://www.tactical-life.com/news/uss-556mm-rifles-not-suited-to-warfare-in-afghan-hills/#:~:text=But%20a%20U.S.%20Army%20study,600-800%20meters)%20apart.
2017
https://www.foxnews.com/world/long-range-afghan-firefights-prompt-us-army-rethink-of-reliance-on-workhorse-m-4-rifle
2019
https://www.realcleardefense.com/articles/2019/01/28/army_vs_marines_which_service_had_the_better_bullet_114140.html
"None of the M855’s shortcomings is surprising, said Don Alexander, a retired Army chief warrant officer with combat tours in Iraq, Afghanistan, Bosnia and Somalia.
“The bullet does exactly what it was designed to do. It just doesn’t do very well at close ranges against smaller-statured people that are lightly equipped and clothed,” says Alexander, who spent most of his 26-year military career with the 5th Special Forces Group."
"Paul Howe was part of a U.S. military task force 15 years ago in Mogadishu, Somalia’s slum-choked capital, when he saw a Somali fighter hit in the back from about a dozen feet away with an M855 round.
I saw it poof out the other side through his shirt," says Howe, a retired master sergeant and a former member of the Army’s elite Delta Force. “The guy just spun around and looked at where the round came from. He got shot a couple more times, but the first round didn’t faze him.”
With the M855, troops have to hit their targets with more rounds, said Howe, who owns a combat shooting school in Texas. That can be tough to do under high-stress conditions when one shot is all a soldier might get.
“The bullet is just not big enough,” he says. “If I’m going into a room against somebody that’s determined to kill me, I want to put him down as fast as possible.”
"These carbines had shorter barrels, usually around 14.5 or sixteen inches, which gave them lower muzzle velocity compared to the full twenty-inch barrel of the M16. The lower velocity of these carbines led to incidents such as those in Mogadishu where the M855 fired out of a CAR-15 failed to fragment and put targets down reliably.
The issue of M855 lethality continued to plague the military in the post-9/11 era. As the wars in Iraq and Afghanistan dragged on, the U.S. Army and Marines began to issue out M4 Carbines, which use a 14.5-inch barrel, in larger numbers. This only exacerbated the problem with M855."
Special Operations Forces were already well aware of the limitations of M855 in short 5.56 rifles following their experiences in Mogadishu. They already had an alternate bullet in the form of the Mk262, a seventy-seven grain open tip match round originally issued with the Mk12 SPR, a version of the M16 designed for precision fire."
"A U.S. Army study found that the 5.56 mm bullets fired from M-4s don’t retain enough velocity at distances greater than 1,000 feet (300 meters) to kill an adversary. In hilly regions of Afghanistan, NATO and insurgent forces are often 2,000 to 2,500 feet (600-800 meters) apart.’