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For centuries, the main battery, or armament of naval warships was the gun. For most of that time, it was the relatively simple cast iron or brass  muzzle loading black powder cannon firing iron cannon balls at relatively short ranges. With the invention of smokeless powder, coupled with the introduction of quality steel, gunnery in the span of two generations or so made incredible leaps in range, accuracy and complexity.

The 16” naval rifles of the mighty Iowa class battleships are probably the most famous modern naval guns, but for my money, the pinnacle was reached with the automatic Mk16 8”/55 caliber guns of the Des Moines class heavy cruisers.

Only three ships of the class were built (the rest were cancelled with the end of World War II) but the USS Newport News would go on to serve until 1975, the last of the all gun cruisers in US Navy service.

Since the big gun cruisers are gone, current standard US Navy gun is the rather anemic Mk 45 5” gun, in both its 54 caliber and recent 62 caliber varieties. The M45 tosses a 70 pound projectile about 13 miles, and has a rate of fire of about 15 rounds per minute.

The Navy has invested vast sums over the  last 20 years or so developing the Advanced Gun System, a 155mm/62 caliber gun designed to fire the Long Range Land Attack Projectile, or LRLAP.

 

While the AGS and the LRLAP offer a substantial warhead with a range of about 59 miles, the problem is, the AGS can only fire the LRLAP. It cannot fire existing 155mm ammunition. That limits it to strictly a land attack role.

The Navy has been closely watching the performance of the Army’s guided Excalibur 155mm projectile. And they’re also looking forward to soon having a practical electromagnetic rail gun ready for sea. Now, a rail gun is pretty useless without ammunition. So the Navy decided to start looking for what could be used. They’ve basically decided to go with a subcaliber, saboted dart. The result if the Hypervelocity Projectile, or HVP.

But this is where our story gets kind of interesting. Since guiding a gun projectile is something that has already been figured out, the Navy and its contractor, BAE Systems, decided to make the HVP guided. After all, great range is not worth a lot if there isn’t great accuracy on the impact end. And while the projectile is a good deal smaller than a 155mm round, they still found space to pack in a small bursting charge.

The Navy also pretty quickly realized that such a projectile could easily be adapted to be fired from not just a future railgun, but also its entire existing inventory of 5” guns. Even better, a version for the AGS could be built. And why stop there? Why not build a version for the Marines and Army 155mm artillery pieces?

As Spill and I were discussing this yesterday, he brought up a very good point. While the program currently is for land attack projectiles, it’s not going to be very long before someone has the bright idea to use this as an Anti-Surface Warfare weapon. The gun has for many years been a secondary armament against ships, with the anti-ship missile forming the main battery. And while that’s likely to stay true, a 5” gun with a range of 50nm and a rate of fire of 20 rounds a minute is going to pose a real threat to any surface ship out there. One or two rounds probably won’t cause too much damage, but a series of hits would quickly place all but the largest ships out of action. Further, the HVP’s speed and small size means there will be little or no means to defeat it before it impacts the target.

It will be interesting to see what the next few years bring.