There are three 57mm guided rounds that were being offered for the USN.

ORKA from BAE has an IR seeker and pop-out fin steering.  It seems fairly conventional but with a flexible seeker that combines autonomous imaging IR and a semi-active laser receiver in one unit.

ALaMO from L3 had some unspecified guidance mode (something RF to judge by the lack of a glass seeker nose) and a fairly unusual mass counterweight course correction system.  It apparently has 4 "bolts" that can be ejected laterally to redirect the round, like the side thrusters in PAC-3.

These two are primarily anti-surface rounds for small boat targets, though both are said to have some anti-air capacity against UAVs and helicopters. ALaMO won a USN competition and is on the way to being type classified and deployed.

MAD-FIRES from Raytheon is a different beast.  It's primarily intended for antiship cruise missile raid defense.  Again, they're being cadgey about guidance, but it seems to be some sort of semi-active radar.  Big selling point seems to be the ability to redirect following rounds in flight to reengage targets that survive a first intercept attempt.  The technology may also have application to Army guns in either 50mm or 30mm.

gatnerd said:

A 155mm version of the HVP was recently fired from an Army Howitzer to shoot down a Cruise Missile in training:

In the same tests, they also fired HVP from a Navy 127mm deck gun and something that looks like a 155mm Advanced Gun System test rig.  

It's been intriguing to watch the pivot; when HVP was announced a few years ago, it was sold as an extended range anti-surface round, but this test shows the transition to air and missile defense has been fairly complete.

taschoene said:

It's been intriguing to watch the pivot; when HVP was announced a few years ago, it was sold as an extended range anti-surface round, but this test shows the transition to air and missile defense has been fairly complete.

Thats a welcome change in my book. It shows that the US is finally waking up to the threat posed by Chinas fireworks factory of anti-ship missiles. Of course, if they were really waking up to the threat, they'd be putting more emphasis on Cruise Missile Submarines rather then trying to overcome anti-ship missiles with their current plan of more ships. 

Along those lines, I hope MAD-FIRES comes to fruition, as that does seem the most promising cannon candidate for stopping missiles. 

Anti Missile use presents an interesting tradeoff for 'optimum' cannon size.

57mm MK3: 220rpm, 120rd magazine, ~10km range

76mm Super Rapid: 120rpm, 80rd magazine; ~20km range 

5": 20rpm, 20rd magazine, ~50km range

Smaller guns offer higher rate of fire and magazine capacity, but less range for interception, and lower probability of destroying / deflecting the missile. 

Larger provide a further interception range, and higher stopping power, but offer a substantial reduction in magazine capacity and rate of fire. 

I am a bit skeptical about there being such a large difference between 57mm and 76mm effective range.  The usual numbers cited for the two suggest a difference of about 10% when comparing basic HE projectiles. (i.e., 76mm HE surface range about 18 km, 57mm HE surface range about 16 km, with similar ratios for air targets).  The comparison gets a bit muddied because of the sabot rounds on offer for the 76mm gun.  But MAD-FIRES is rocket-assisted, which should mean more range and a much faster/flatter trajectory than ballistic 57mm rounds and probably at least comparable to the saboted 76mm DART rounds.  The PR video that is out there seems to show MAD-FIRES as a hit-to-kill weapon, suggesting that "stopping power" isn't a huge differentiator-- no ASCM is likely to survive a direct impact from a 57mm round intact.

The use case for 127mm-155mm HVP is different, from these others.  It's seen as a potential ASBM/TBM killer, as well as an area defense against high-speed cruise missiles.  It actually plays in the same regime as much larger weapons like SM-6 or Patriot PAC-3. 

HVP may also retain an anti-surface capability, but the HE load is disappointingly small for that role.  OTOH, a smart fuze could make it interesting -- a round that detonates deep inside a ship after penetrating from above could be very nasty.)

gatnerd said:

Also makes me wonder about the potential for a 57mm armed Tank/IFV that could provide both ground attack and air defense capability...

Absolutely amazing no one has thought of that before. 

And let's not mention 57 mm auto grenade launchers with a dual feed APFSDS and airburst/Impact fragmentation/HESH rounds.

Red7272 said:

Absolutely amazing no one has thought of that before. 

Those are both really cool. What are the models of those respective machines?

T15 heavy IFV and Derivatsia SPAAG based on BMP3 hull.

The T15 57mm is really an awesome vehicle.

-Most of the protection of a Tank

-Can carry infantry like an IFV

-57mm cannon allows 'overmatch' against IFV armor, while HE shells allow superior anti personnel / anti structure effects compared to traditional 25-30mm cannons. Airburst ammo + high gun elevation allows IFV to protect troops from UAV's and helicopters. 

-Missile tubes for firing Anti Tank and (presumably) and option for MANPAD size AA missiles, for protecting the IFV from Tanks and/or aircraft 

-Assumed? some spare parts commonality with the T14 MBT for simplified logistics 

I haven't been able to confirm if the T15 has the same Radar system as the T14, but if it does, major wow, as that would allow it to track both incoming projectiles and aircraft. 

All in all it seems like one of the most versatile armored vehicles ever produced.

Radar on the side of the 57mm is not for detecting or searching of aircraft but for Ballistics measurements,similar radar can be seen on some of the 152mm cannon Coalitsia variants , its used to tracking and ranging the shot and correcting the fire solution.

The Armata program is currently suffering delays some due to cost but also due to huge issues developing the Engine for the platform. Since 1930's the evolved the V-2 engine powers most Soviet/Russian tanks, so i wouldn't be surprised if at some point someone decides to uprate the V-2 yet again to 1800HP , they want for Armata or easier jet fit a 2000hp gas turbine