islandphish:
So how awesome is 5.7 when you use larger bullets and crank 'em up?
The 5.7x28 ammo has been noted to be extremely sensitive by those who reload it. To be expected with higher pressure ammo using light bullets.
You cannot really use larger bullets and still retain the velocity the round requires to achieve the little it does. The rounds works on velocity, reduce that velocity to go heavier and it gets even worse.
It will always be much weaker than a .223/5.56 round, it works on lower pressure, has less than half the case capacity, and is typically used from shorter barrels.
It has about 2/3 the velocity of the .223/5.56 with the light intended bullets, and much less if you start going heavier. You cannot simply swap in typical .224 bullets in typical .223/5.56 weights without seeing seriously degraded performance.
Yet another problem with the ammo is that while it may appear to have high penetration, penetration of thin barriers like soft armor is very different from penetration of fluid-like tissue. Pointy and hard projectiles at high velocity and minimal frontal area penetrate thin barriers, while momentum and sectional density tends to penetrate tissue. Momentum on such light rounds is limited.
The rounds as designed just have enough penetration in soft tissue with the specifically designed FMJ rounds that also penetrate soft armor.
Gel tests show around the desired 12" gelatin penetration with the specifically designed military/LEO FMJ rounds. (And gelatin has no bones or tissue density transitions that reduce that number in actual applications.)
If someone was to use JHP ammunition against targets even without body armor the penetration would be far less than desirable.
You would end up with what is essentially a potent .22 varmint round best limited to small game.
So
users are stuck with FMJ even against unarmored targets.
A FMJ .22 much less powerful than your typical .223/5.56 round.
Like I said in the prior post, that may be adequate at 15 rounds per second with almost no recoil on full auto in the intended PDW application, but is pretty pathetic in semi-auto.
Even worse with JHP rounds as typically sold to average Joes.
MP7 said:
A SWAT member will have 5 or more rounds on target
instantly. And if the gelatine tests do really show
it has more piercing and less overpenetration ...
... then i think it is obvious, what the improvement
is over an Mp5 or an M4.
I think the P90 has better ballistics than the MP7 and uses a more common bullet caliber (.224 same as the .223/5.56 just shorter and lighter).
This was also the conclusion of NATO testers.
The MP7 is better for concealment and I see little benefit in some sort of paramilitary raid where concealment does not matter.
The 4.6x30 bullet is so tiny. 5.7mm is a .22 caliber, 4.6 is .183 caliber, or slightly larger than a .177 pellet for a pellet gun (with a filled in bullet shape instead of a wasp shape). High velocity pellet gun.
Another problem with PDWs is well trained individuals have typically been taught a lot of trigger discipline using subguns, especially for hostage type scenarios where accuracy is critical.
The PDWs though have such inferior ballistics compared to an old 9mm subgun against an unarmored target, and especially compared to an M4, that you really need more rounds to do the same thing.
What 1 round of .223/5.56 JHP or 2-3 rounds of 9mm JHP would do against an unarmored target may take around 5 or so 5.7x28/4.6x30 FMJ rounds.
2-3 rounds at a time in training may look cool and be precision aimed with a PDW, but may prove less than adequate when actually used to immediately stop a threat.
So while PDWs may be useful in a full paramilitary assault where they plan to spray at the target, they would be less useful with hostage scenarios or with hostile threats mixed with non-combatants using traditional subgun tactics.
I think that generally makes them less ideal for a SWAT type team.
I actually think the P90 rate of fire should be pushed up towards the 1200 RPM mark to compensate vs the 900RPM area and the limited recoil of the round should still make that extremely controllable putting 5 rounds on target in a quarter of a second. However that would give slightly less impressive demonstrations against paper or one handed.
Demonstrations I am sure are more important to sales than the real world performance increase.
