Tim over at MAC is doing a comparison, based on available similar physics rifles, of the new 277 Fury’s armor defeat capability.
Now, a caveat he does explain (although I think he could do so a little better) is that this test is based on only one aspect of armor defeat capability, velocity.
Speed can beat armor, getting a conventional projectile going fast enough and that is usually enough to grind through soft or hard armor with lead or copper.
What this test doesn’t test, because it cannot test it with the Army projectiles being kept under wraps and not commercially available, is special materials rounds.
M855A1 and M80A1 haxe exposed hard steel penetrative tips, this material choice changes the raw physics package being delivered to an armored plate. This allows the slower and or lighter rounds more levels of armor and at greater distances/slower speed than the raw copper and lead or the softer jacketed over steel of M855/SS109.
So really. This test is more realistic to asking will the commercially available ammo defeat rifle armor. Especially the hybrid high pressure stuff that will have the extra velocity.
Short answer, about as well as current conventional rounds. Which is to be expected.
It will punch soft armor at pistol and magnum/shotgun ratings like rifle rounds do, and it will be stopped by the III and IV plates based on the velocity at impact. I suspect it will crunch through III rated plates like M193 and M855 can at comparable speeds but will start getting stopped below a predictable velocity threshold.
The same goes with IV’s, although I suspect IV will probably stop 277 with high probability, as we see in this test.
We’re back to the two parts of armor defeat, material and velocity. The velocity on its own is going to place it into the high velocity rifle performance tier we understand well, 5.56 and 5.45 live here as well as many magnum calibers. The hardened steel of the military 135gr projectiles are what undoubtedly give it the performance the Army wanted.
Remember that the Army had the projectile already, they gave it to the NGSW participants to build around. The commercial ammo is merely going to be, essentially, an efficient magnum caliber thanks to the new safe pressures the hybrid case allows. Rifles chambering the hybrids are going to need to be reproofed at the higher pressure to see that their designs can withstand it, but I suspect that in most instances this won’t be as challenging an adaptation it may seem. Especially if we’re only taking pressures to current proof load levels like 80,000 psi.