This got me thinking, because another round has also had very inconsistent reviews - the 5.56 SS109 "Green Tip." Some reports from the field indicated that it worked extremely well, while others reported the rounds going "through and through" with little effect even at CQB ranges.
What makes this even more interesting is that the 5.7x28 SS190 is basically a lightweight clone of the 5.56 SS109: both rounds feature a small steel nose cone, followed by a softer material base. And, further adding to the intrigue, both are designed by FN, and both are designed to penetrate a few inches and then tumble.
5.7x28 SS190: Steel nose cone, aluminum base.
5.56x28 SS109: Steel nose cone, lead base
A few years back, the Army did a multi million dollar study on why the 5.56 was having such issues, and after lots of high speed photography, it was discovered that the issue was the Fleet Yaw effect:
"What resulted from their investigation was a landmark discovery in terminal effectiveness science: Bullets – all bullets, not just .22 caliber ones – experience a period of very violent yaw and turbulence when they exit the muzzle, causing their angle of attack relative to their flight path – that is how “straight” the bullet is in flight – to vary wildly. Within 50m, they found, two bullets fired from the same gun, at essentially the same time, might impact a target at two completely different angles. A bullet impacting head on into gelatin would stay stable for much longer than one impacting at a high angle, and would deposit its energy much later. This explained the problems some users – but not others – were having with their weapons. In some instances, the FMJ projectiles would hit the target at a desirable high angle of attack, tumble and fragment within a short distance, and reliably stop the target, while in others, the same type of projectile would hit at a flat angle, and might not yaw for many inches."
http://www.thefirearmblog.com/blog/2014 ... ctiveness/" onclick="window.open(this.href);return false;
Hypothesis: The reason the 5.7x28 has gotten a bad rap in Mil/LE circles is due to the Fleet Yaw Effect of the SS190 projectile, not due to a "lack of power."
If the 5.56 SS109 is nearly identical in construction to the 5.7x28 SS190, and the 5.56 SS109 and 5.7 SS190 are both known for unpredictable performance, then it is likely due to the same case - the Fleet Yaw Effect.
I believe we can see the Fleet Yaw in action in Buffman's excellent test of the SS190: the round penetrates nearly 10" of straight gel before tumbling:
https://www.youtube.com/watch?v=56lSi8C9rT8" onclick="window.open(this.href);return false;
Given that the 5.7X28 is typically not used against the morbidly obese, it's fair to assume that this SS190 would have been a "through and through" with the same poor performance often sited by users of the 5.56 SS109, simply poking a 0.22" hole with little energy transfer or effect.
And performance like this would explain why the 5.7x28 has gotten such mixed reviews from LEO/MIL who use the SS190.
Implications and Solutions: The Army has solved the Fleet Yaw problem through the use of OTM projectiles such as the MK318 and MK262, as well as the 3-piece M885A1. LEO's meanwhile have solved it through the use of JSP's and hollow points.
For the 5.7x28, ballistic tip projectiles such as the VMAX are similarly yaw independent, as JHP's.
However, given the 5.7x28's raison d'etre on penetration followed by yawing, what needs to be established is a FMJ/OTM/Solid that less prone to the Fleet Yaw effect than the SS190.
So far the SS195/SS198 projectile looks pretty good, but a larger test sample is needed, fired at a variety of ranges, to determine whether the SS195/SS198 is vulnerable to fleet yaw. For example, 50 shots of ss198 into a "clear ballistics torso" - with 10 rounds each at 5, 10, 15, 20, 25 yards to determine whether they are all consistently tumbling at the same depth, or whether Fleet Yaw is still in effect.
Moving beyond that, it would be ideal to create a new Duty round that is both designed to counter fleet yaw, while offering penetration and 12" FBI minimums. Because as it stands, SS190 is likely just as vulnerable to fleet yaw as it's big brother SS109, and so long as SS190 remains the dominant duty round for the 5.7x28, the platform is likely to not receive the respect and continued support that it deserves due to inconsistent performance.
