Battery AMTB - Gravelly Beach

Battery AMTB - Gravelly Beach (1944-1946) - Battery AMTB - Gravelly Beach was a reinforced concrete World War II rapid fire 90mm gun battery on Fort Baker, Marin County, California. Battery construction started 29 Jun 1943, was completed 6 Sep 1943 and transferred to the Coast Artillery for use 18 Jan 1944 at a cost of $ 4,907.63. Deactivated in 1946.

Battery AMTB - Gravelly Beach Emplacement #2 from Above
Battery AMTB - Gravelly Beach Emplacement #2 Mounting Bolts
Battery AMTB - Gravelly Beach Emplacement #2 from the Beach

History

Part of the Harbor Defense of San Francisco.

The AMTB battery at Gravelly Beach consisted of two 90mm guns mounted on 90mm M3 fixed gun mounts and two 90mm guns on mobile M1A1 carriages. Concrete pads for both the fixed guns were constructed. The battery had a dual mission of defense against fast enemy motor torpedo boats and enemy aircraft. The effective range of the guns was about 8,000 yards. Each weapon required a crew of 15, 9 men in the gun squad and 6 men in the ammunition squad.

The above photos were taken at Fort Monroe, Battery Parrott

From FM 4-91: "This weapon consists of the 90-mm gun M1 and top carriage M1A1 on the 90-mm gun mount M3. The mount M3 is of the turret type, the shielding being constructed of boiler plates. This boiler plate shield provide fragmentation protection only. No shielding is provided at the rear due to the requirements for service of the piece. A sighting port in the shielding in front permits sighting in direction by the gun pointer."

References:

FM 4-91 - 90-MM Gun, Fixed Mount Service of the Piece
FM 4-126 - Antiaircraft Artillery, Service of the Piece, 90-mm Antiaircraft Gun
TM 9-373 - 90-mm Gun M1 and 90-mm Gun Mount T3 (M3)

**Battery AMTB - Gravelly Beach Armament** (edit list)
Empl No	Caliber Type	Barrel Length	Model	Serial No	Manufacturer	Carriage	Service Dates
1	90mm Rifle	186.15"	M1	6915	General Motors	Pedestal Mount, M3, #100, Fisher	1944-1946
2	90mm Rifle	186.15"	M1	6924	General Motors	Pedestal Mount, M3, #109, Fisher	1944-1946
Source: 1. RCW Form 1, Oct 1943 2. CDSG 3. Berhow, Mark A. ed, American Seacoast Defenses: A Reference Guide, 2nd Edition, CDSG Press, McLean, VA, 2004, ISBN 0-9748167-0-1, pages 80-81, 217. 4. Armament Data - Harbor Defenses of San Francisco, undated, NARA RG165, E257 Box 68 - Bolling Smith.

Current Status

Part of the Golden Gate Recreation Area (GGNRA) administered by the National Park Service. No period guns or mounts in place. One concrete pad is exposed and the other is visible.

Context

Location: Fort Baker, Marin County, California.
Lat: 37.827° Long: -122.489° Elevation: 48' Bing, Google, OldMapsOnline, USGS, OHM

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Sources:

Kent, Matthew W., Harbor Defenses of San Francisco - A Field Guide 1890 to 1950, Copyright 2009, Blurb, ISBN 978-1-61584-163-9, page 148.
Berhow, Mark A. ed, American Seacoast Defenses: A Reference Guide, 2nd Edition, CDSG Press, McLean, VA, 2004, ISBN 0-9748167-0-1, pages 80-81, 217.
Armament Data - Harbor Defenses of San Francisco, undated, NARA RG165, E257 Box 68 - Bolling Smith.

Links:

CDSG