The Navy League’s online magazine Seapower is reporting that ” The Navy is installing a co-axial 7.62 mm machine gun on the mounts of its Mk38 chain gun systems, a Northrop Grumman official said….the addition of the co-axial Mk52 machine gun gives the gunner another “right-sized” option for countering a small target, such as pirates or terrorists on jet skis…Northrop Grumman is installing the Mk52 guns in the Mk38 under an indefinite delivery/indefinite quantity contract.”
This has been proposed for several years now, but this is the first indication it is happening. The proposed weapon, the 7.62mm Mk52, is in fact an electrically powered chain gun like the 25mm Mk242. (The article appears to be incorrect in this regard.)
The article also discusses the possibility of upgrading the Mk38 by replacing the 25mm gun with guns of 30 or 40mm.
I think the Coast Guard could make a good argument for upgrading its Mk38s to 40mm. The change would make very little difference to a DDG, also equipped with a 5″ gun and anti-ship missiles, but the Mk38 is the largest weapon available on about 75 Coast Guard cutters and these cutters could at any moment be required to face a vessel much larger than the Iranian boats the Navy has been fixated on. We already know the 30mm is a quantum leap in capability compared to the 25mm. Effectiveness is closely related to projectile weight. The 30mm projectile weighs about twice that of the 25mm. The 40mm projectile will weight three to four times as much as the 25mm. Since the rate of fire for these guns is similar, the 40mm is likely to be at least three times as effective against more difficult targets and also has a greater effective range.
The Coast Guard plans to install the Mk 38 on 64 Webber class and 25 Offshore Patrol cutters. The older crew served version of the Mk38 is on the remaining 378s, the 210s, and the remaining 110 foot Island class WPBs. I expect we may see the Mk38 on the Polar Security Cutters and the 87 foot Marine Protector class WPB replacement when they are built.
This would of course be less important if the vessels had something like the Long Bow Hellfire, which would be more effective than any of these guns against virtually any size targets.