Re: [MV] Amphibious Gamma Goats

Richard Notton (
Tue, 26 Oct 1999 09:30:22 +0100

-----Original Message-----
From: Daniel Terp <>
To: <>
Date: 26 October 1999 00:52
Subject: [MV] Amphibious Gamma Goats

We were talking about amphibious vehicles, and someone mentioned that
the M561 Gamma Goat was amphibious.

This has always confused me as I've never seen anything that looks
less like a boat than an M561. DUKWs, GPAs and LARCs all have that
boat-with-wheels look, but the M561 doesn't look the least bit
You will find the FV620, 622 and 623 also distinctly un-boat like but wholly
amphibious without preparation.

One of my friends postulated that the amphibious capability may be
more of an "extended fording" thing, able to cross small streams and
ponds and such, but not lakes.
After the experiences of W.W.II and European rivers, both the British and US
planners were concerned with intrinsic deep fording and some amphibious
capability. It did become a NATO requirement in the 60's stemming from their
perceived threats in Europe that WWIII would be fought on the German plains and
the viability of river crossings would be of enormous strategic importance.
This requirement was retained until the operation of heavy lift helicopters
could be assured, this saw the FV620/2/3 in service until the 80's.

Even if it floats, with no prop and just the wheels for propulsion I
expect the going would be painfully slow. And there's so little
freeboard, it would certainly be a calm water thing.
The prototype FV620 went down that line too but quickly acquired water jets to
achieve reasonable speed whilst thereby keeping the propulsion system well out
of harms way during severe cross-country operations.

Is there anyone out there with first hand knowledge of the Gamma Goat
that can provide more info on just how amphibious it is?

(interestingly, Thomas Berndt's "Standard catalog of U.S. military
vehicles" says it's amphibious, but lists it with 1.5 ton trucks, not
in the amphibious section)
The FV620 was evaluated with the M561 together with the M113 and FV432 in the
1967 "Mudlark" trials in Thailand, this extensive and fascinating report is to
be found in the military archives here. The M561 proved to be rather unreliable
and of too small payload when pitted against the FV620's unprepared 5 ton
capability (although limited to 4 tons in service for amphibious use), and
somewhat slow in the water since the 620 makes about 6.5 kts with a further
improvement with Dowty jet drives in the FV622/623 to 9.5 kts together with an
internal front winch and improved visibility in this later variant.

Even so, these vehicles were only intended for rivers and sheltered esturine
waters, later experiments to equip the FV622's with boat-like hull extensions
for rougher waters were rather unsuccessful and did not go into service.

(Southampton UK)

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