Wow, OK so I guess that ammo is performing as expected.
More like it wasn't performing any worse than allowed by that particular Army standard.
Your 55gr ammo might group better in a rifle designed to shoot the 55gr bullet. Each bullet weight (and length) has an optimal twist rate, and will work, to a degree in a range of twist rates. For some bullets that range is wider than others.
Yes, it is possible to spin a specific bullet "too fast". Even a "solid" bullet is still a pointed cylinder being spin around its notional long axis. And nothing made by man is 100% perfect, so the faster it us spun the greater the effect of any imperfections on the "wobble".
Some years back I got several boxes of the Sierra 63gr "semi spitzer", They were the "deer bullet" in .22 cal, at the time. Shot some from muy .22-250. Regular Win M70 varmint, with the twist for the 50-55gr slugs. That rifle, 3/4" with 55gr sp and less with the match 52/53gr HP bullets.
The long semi spitzers shot into 2 inches never really any better. Minute of Deer so all things considered, I wasn't unhappy.
Now everyone says this was because of the twist in my rifle being "too slow" for that bullet, and they're probably right. So, if there is a "too slow" then there must also be a "too fast".
Traditional "cup and core" bullets will come apart from too high a rotational stress. How much is too much depends on the construction of the bullet.
The current standard is 4moa. That being said, I’ve touched a ton of rifles stamped US Property, from M16A2s, to FN manufactured M16A4, to Colt M4s (whatever version we’re on now, all the same over the past 20 years imo). Never found one that shot worse than about 2moa.
I don't doubt that a bit. The construction of the A2 and variants generally are more accurate than the original M16 and A1.
I never saw, or heard of any of the rifles back then being tested before deployment, and I saw a lot of them go, and saw them overseas. We inspected them, but no one ever shot them to see if they "official standard" was met.
I was a Small Arms Repairman (45B20) from 75-78, Never once had a weapon brought to the shop for any accuracy issue. Function was the rule, and no live fire testing was ever done anywhere I served or ever heard of.
I'm talking about line units and their support, not specialty work like the Marksmanship shop making match rifles.
I think it quite likely that not only were rifles not tested before overseas shipment, but that none of them would have failed, had they been. There are things where the Army has a standard, just to have a standard...
