When I started this series about some of the weapons I thought would be most appropriate for cutters, I knew one of the choices would be a larger caliber gun equipped with air-burst munitions, but I was thinking 30mm. That is still an option, but the 50mm would be, oh, so much better for engaging every possible threat, and here we have evidence it may be much better for engaging UAS, extending the range so that it is not only capable of self-defense but can also protect other assets.
WHAT ABOUT THE 57MM? While the Webber class WPCs probably could accept a 57mm Mk110, the guns and ammunition are very expensive and the gun weighs about eight tons plus the weight of ammunition and fire control. The 50mm is probably the largest caliber that could be added without a major rebuild.
Comparison of 50mm Bushmaster III with the 30mm Bushmaster II. By comparison the 25mm’s length over all is 105.2 in (2.672 m) and its barrel length is 85.6 in (2.175 m)
The NORTHCOM online magazine, The Watch, reports,
U.S. defense firm Northrop Grumman is testing higher caliber cannon rounds to shoot down drones at a lower cost, based on feedback from Ukrainian Soldiers who are increasingly facing swarms of high-flying unmanned aircraft, a top company executive told Reuters.
What they are looking at is improving a successful system by using a large caliber gun to increase its effective range. (See the video above.)
“They love the (anti-drone) system. They want more range because they want to shoot these things down further out, which completely makes sense … So we’re taking that feedback,” …Northrop Grumman’s Bushmaster cannon uses 25 mm and 40 mm rounds and could shoot down drones up to a 3-mile distance but increasing the caliber to 50 mm would significantly broaden the range, even five-fold, O’Bryan said
It has been years since we talked about the 50mm version of the chain gun, but it really looks like a significant step up from the 25mm, and yet it is appears to be doable.
The 50mm has about twice the effective range of the 25mm. The weight of the projectile is about ten times greater. It might even be possible to make an ALaMO version of the 50mm round. It would also probably be more accurate. Certainly the kill radius when the shell bursts is much greater. Currently I don’t believe there is an airburst round for the 25mm.
These are the previous posts discussing this weapon:
- 40 and 50 mm Chain Guns, April 2019
- 50mm Chain Gun, More Detail, April 2019
- More on the New 50mm Chain Gun, and Maybe Counter-UAS, Sept. 2021
Right now the 50mm XM913 is an Army project, but it is going to be made in large numbers as it will arm the replacement for the Bradley Infantry Fighting Vehicle (IFV). The 50mm XM913 is the latest version of the chain gun series, which includes the M242 25x137mm Bushmaster Chain Gun that is used in the Mk38 machine gun mount that arms many Coast Guard cutter. Users of the new weapon would benefit from weapon training and maintenance commonality with the M242.
We might be able to get the Navy’s attention if we prototype the first installations on the PATFORSWA WPCs.
Chuck Hill's CG Blog 
Thanks for the update Chuck!
I really hope they figure out how to handle these drone threats before it’s too late.
Do you think this would be effective on surface targets as well? I know you’ve shared a lot of info on that subject. It would have to be a different round, obviously.
I know the GM’s on the Gallatin were excited when they got to use our 20mm a few times to disable/sink smaller vessels. I’m sure that today’s newer rounds would be much more effective.
Matt
Matt, There is a lot of effort going into countering UAS. Love the idea of zapping them with energy so that you have an unlimited magazine but that may never work as advertised.
Meanwhile I would like the weapon to work against the entire range of threats.
The Programable Airburst Munition is just an adjustable time fuse that triggers an explosion after the round has traveled the distance the firecontrol says it should fly to meet the target. It should also explode on impact. I estimate the projectile should weigh about four pounds. That is ten times what a 25mm projectile weighs. Still a lot smaller than the projectiles of some of our previous weapons: 5″/38 were 55 pounds and 76mm guns were 14 pounds.
The Armor Piercing Fin Stabilized Discarding Sabot round is just dense metal arrow without explosives. It might damage steering or an engine, but hitting a large ship in any of the mostly empty space above the waterline isn’t going to do much.
When I think of a maritime terrorist attack, my first thought is that the ship is some sort of bomb–explosives, LNG, poison gas–and the ship has a specific target it has to get to, so getting a mobility kill is the primary objective. That is difficult because most of the key components are below the waterline.