Battery AMTB - Cape Disappointment (1944-1946) - Battery AMTB - Cape Disappointment was a reinforced concrete World War II rapid fire 90mm gun battery on Fort Canby, Washington. AMTB stands for Anti Motor Torpedo Boat. Battery construction started 10 Jun 1943, was completed 24 Dec 1943 and transferred to the Coast Artillery for use 5 Apr 1944 at a cost of $ 10,031.05. Deactivated in 1946.
The AMTB battery at Cape Disappointment consisted of two 90mm guns mounted on 90mm M3 gun mounts. Concrete pads for both these guns were laid near the end of the south jetty. 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.
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)
U.S.Army, Supplement to the Harbor Defense Project Harbor Defenses of the Columbia, (CCA-AN-CR), 12 Aug 1946, CDSG
Rounds Fired - Seacoast Artillery Including Proofing Rounds, HQ Harbor Defense of the Columbia, undated, NARA RG165, E257 Box 68 - Bolling Smith.
Berhow, Mark A. ed, American Seacoast Defenses: A Reference Guide, 3rd Edition - PDF, CDSG ePress, McLean, VA, 2012, ISBN 0-9748167-0-1, page 80-81, 218.
