Vice Admiral William S. Sims, Commander, United States Naval Forces Operating in European Waters, to Naval Forces Operating in European Waters
U.S. NAVAL FORCES OPERATING IN EUROPEAN WATERS,
U.S.S. MELVILLE, Flagship,
15, June 1918.
CIRCULAR LETTER NO. 49.
From: Force Commander.
To : All Forces.
Subject: Depth Charges Mark II – Use of.
1. The following letter from the Bureau of Ordnance is quoted for information:-
“1. Subsequent to publication of Ordnance Pamphlet 336-A, descriptive of the depth charge Mark II, further experiments have shown the advisability of modification of the depth charge instructions contained therein.
2. Three-hundred-pound depth charges may be dropped with safety from staunch vessels at speeds less than the fifteen knots originally prescribed [i.e., prescribed]. Trawlers have used these depth charges at speeds as low as five knots without substantial injury to the vessel. It is presumed safe, therefore, for vessels of greater strength than patrol boats and submarine chasers to use the Mark II depth charge down to a minimum speed of eight knots. Submarine chasers should not drop them at less than twelve knots. Patrol boats, by reason of their slow speed and frail construction, will not be issued the heavy depth charge, but the issue of the Mark I depth charge to such boats will be continued.
3. Depth charge Mark II will countermine from explosion of another charge if at a distance from the exploding charge of 130 feet or less. Over 200 feet, however, there is no danger of countermining effect. It is suggested that instructions be issued calling attention to this fact and requiring that in laying a chain of depth charges the time interval between successive depth charges be such that the laying vessel will proceed not less than 200 feet between successive charges. (This represents eight seconds for 15 knot vessels, twelve seconds for 10 knots, etc.)
4. Care should be taken not to drop depth charge between four seconds after firing of a Y-gun and the explosion of the Y-gun charge. Depth charges, however, may be safely dropped simultaneously with the discharge of the Y-gun.
5. The rate of sinking of the Mark II depth charge is approximately six feet per second.”
Source Note: Cy, DNA, RG 45, Entry 517B. At the top of the page in vertical fashion is stamped the word “CONFIDENTIAL” and horizontally along the top “INDEXED.” After Sims’ signature is a distribution list: “Copies to:-/Brest 75/Gibraltar 35/MELVILLE 75/Aviation (Captain [Hutchinson I.] Cone) 30/Azores 15/Captain [Richard H.] Jackson [United States Staff Representative in Paris] 2/Commander Mine Force [RAdm. Joseph Strauss] 28/Sixth Battle Squadron 11/C.O. Receiving Ship, Liverpool [Cmdr. (ret.) Eugene L. Bisset] 2./Base 25 [Corfu, Greece], 45./C-in-C Atlantic Fleet [Adm. Henry T. Mayo] 1./Commander Air Stations in Ireland [Cmdr. Frank R. McCrary] 12/Commanding Officer Base Hospital Two [Capt. Edward S. Bogert], 2./N.P.O. Cardiff [Capt. J. K. Robinson?] 1/Operations 2/Buord [Bureau of Ordnance] 2; Bunav [Bureau of Navigation] for New Destroyers 50/Cdr. Roger Williams Gen. Hdqs. Am. Exp. Fcs. France. 1/C.O., U.S.N., Avi. Det. R.A.F. Killingholme. [Lt. Cmdr. Kenneth Whiting] 1./Files 165.”