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Ordnance Notes -- by Bob Stoner GMCM(SW) Ret.
Mk 18 Mod 0 Manual 40mm Grenade Launcher
Mk 18 Mod 0 40mm grenade
launcher ready for action
aboard a PBR during the Vietnam War. Note the large ammunition box on the
left, that gun feeds from left to right, and the expended cases remain in
the belt after firing.
The first attempt to build a fast-firing
alternative to the single-shot M-79 was the Honeywell Mk 18 Mod 0 multiple grenade
launcher. The Mk 18 fired the same round as the M-79 launcher, the 40x46mmSR,
and not the more powerful 40x53mmSR round used by the later Mk 19 Mod 0. The
Mk 18 uses a split breech system and is manually operated by a hand-crank. The
split breech is actually two pairs of four-lobed starwheels. The tab of its
fiberglass reinforced belt of 24 rounds was introduced into the feedway and
pushed through while the hand-crank was turned to index the first round. Once
indexed, the gun was set on SAFE until needed. Use was simplicity itself: the
safety was set to OFF and the hand-crank was turned. The starwheels drew the
rounds into the firing postion -- centered between the upper and lower starwheels
-- then fired -- and then passed out the ejection port by the rotating starwheels.
The 40mm grenades were not withdrawn from the belt like other machineguns; the
fired cases remained in the belt.
Rate of fire depended on how fast
the gunner could turn the hand-crank. The Mk 18 weighed about 8.6 kg (19 lbs.)
and was 56cm (22.5 in) long. Design commenced in 1962 and nearly 1,200 were
built between 1965 and 1968.
Mk 18 Mod 0 (Honeywell) 40mm grenade launcher
broken down for maintenance by EN2 Ron Simpson
aboard his PBR during the Vietnam War.
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© 2002 Bob Stoner
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