30mm for use at sea?

Just because a gun is 30mm doesn’t mean all 30mm guns use the same ammo. For instance, we often see talk of 7.62mm ammo for small arms. In US usage, we often see it expressed as 7.62mm NATO, to distinguish it from a couple of Soviet made rounds. 7.62mm NATO has a cartridge length of 51mm, where as the Soviets developed first the 7.62mmx54R; that is, a cartridge case 54mm long, with  a rimmed case. The next developed the 7.62mmx39, famous as the ammunition for the AK-47.  The point being, while all are 7.62mm, they aren’t at all interchangeable.

And so it comes to pass that we see ATK Armament Systems is developing a modified variant of the M230 30mm chain gun for possible shipboard use.

The Navy is looking at arming its patrol boats and helicopters with the same withering firepower carried aboard the Army’s AH-64 Apache gunship helicopters.

ATK Armament Systems has modified its venerable M230 30mm chain gun to give naval forces a more potent alternative to the .50 caliber machine gun.

For years, the Navy has admired the Apache’s powerful, nose-mounted 30mm cannon, but the Navy’s strict safety guidelines make the M230’s electrically-primed firing system unsafe for use aboard surface vessels.

As a potential solution, the Navy awarded ATK a contract roughly two years ago to develop a version of the M230 with a more traditional, percussion-primed system.

The M230 is most known as the gun mounted under the Apache helicopter, and has been prominently featured here many times on Daily Dose of Splodey.  Unlike the 30mm used in the A-10’s GAU-8 gun, or the MK46 guns system slated for the LCS and LDP-17 ships (and the cancelled USMC Expeditionary Fighting Vehicle), this round has a relatively low muzzle velocity.  That low muzzle velocity means a depleted uranium or tungsten core penetrator for anti-armor effects is pretty useless. So the M230’s ammo uses HEDP, or High Explosive, Dual Purpose ammunition. HEDP combines the armor penetrating effects of a HEAT round with the fragmentation effects of a conventional HE round.

The need to revert from electrically primed ammo to percussion primed ammo is due to HERO- Hazards of Electromagnetic Radiation to Ordnance.  On board ship, the radar, radios, jammers and other sources of E/M or RF energy have the potential* to cause unwanted current in sensitive electrical systems. Such as electrically primed ammo. Obviously, that would be bad. Rather than going to the trouble of certifying the electrically primed ammo is HERO complaint, why not just go with percussion primed ammo? Further, ditching the linkless feed system for a traditional linked belt system eliminates a good deal of complex machinery that may be needed for the airborne version, but only adds complexity to a surface mount.

As for replacing the M2 .50cal with a 30mm gun, well, it makes good sense to me. Look, I’m as big a fan of Ma Duece as the next guy. But if the target is a small boat, the .50 just doesn’t have particularly good effects. You have to put an awful lot of holes in a boat before it sinks. Especially since most of the holes will end up being above the waterline.  But exploding 30mm HEDP rounds will tend to blow bigger holes in a  boat, be more likely to damage motors, ignite fuel, and disable personnel.

Presumably, the M230LF as mounted would be lighter and less bulky than the Mk38 25mm gun system (which is a high velocity gun system, and hence requires quite a robust mounting to absorb recoil). Ordinarily, I’d say just skip the 30mm weapon system and just use the Mk19 40mm automatic grenade launcher, but it has an even lower muzzle velocity, and that would lower the probability of hitting a small maneuvering target so far that the effects of the larger 40mm round would be irrelevant.  We’ll keep an eye out to see if this system goes into service.

*C WUT I DID THERE? Potential? Electricity jokes on the blog? Shocking!

4 thoughts on “30mm for use at sea?”

  1. Shocking indeed… you’re getting funnier!

    Anyway, you also left out:
    -7.62×63 (aka .30-06 – e.g., Garand, M1903)
    -7.62×25 (Soviet SMG / pistol round – e.g., PPSh, Tokarev TT-25)
    -7.62x38R (Soviet pistol round – Nagant revolver)
    -7.62×17 (aka 7.62 Browning, aka .32 ACP – e.g., whole bunch of stuff)

    (I don’t know that .30 Carbine was ever referred to in metric, though, so it’s not on the list.)

    Also: you wouldn’t happen to know the round weight / muzzle velocity for the M230LF and the Bushmaster would you? Would be interesting to compare the actual energy of firing, and see how much difference there really is in the amount of recoil energy imparted to the mounting.

    1. I’ve misplaced by handy-dandy index of Army ammo, and I strongly suspect it isn’t available open source. Not that the characteristics of the round are particularly classified or anything. I’m just not gonna dig deep enough to find the specs.

      I’m a big picture guy.

    2. meh.

      I’ll hit Wikipedia up later when I have a chance. I’m sure I can find it in there … I got the same data for 20mm a few days ago.

  2. *C WUT I DID THERE? Potential? Electricity jokes on the blog? Shocking!

    Ugh. Good pun, ya got me.

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