IJN depth charge throwing distance

200 feet was a total WAG on my part, CapnMac82 ... based on a few YouTube videos I found of US/UK antisub work in WWII that seemed to indicate something along those lines with US equipment.

But I have no way of gauging how that compared with the Type 94 Y-gun setups as carried on the rather dimunitive No. 13 IJN subchasers. You have a good point though - even with two Y-guns, and two stern racks, the No. 13's could not produce a very dense pattern, or keep it up very long, for that matter.

200' is very close aboard for 100kg charges that could go off as little as 30m under the ship.

Probably, "the book" says something nice and neatly metric, like 75m, which would be a comforting 250' for those having to drive flimsy hulls over serious underwater detonations.

Which probably means that 200' is probably closer to what actually was achieved.  Such fictions are sometime necessary  in Awfully Slow Waiting combat.  Especially with only one, maybe two, "Y" launchers.  

Which configuration does not make much of a "pattern" to put over that best guess of where the sub is--the looking for a black cricket in a black room at night armed only with a blunderbuss being ever apt.   Which is why USN & RN practice was to use "K" launchers in groups of six or eight, which, with stern ramps made a nice, dense, oval pattern around one's datum point.

The question I haven't been able to answer is, how far could these throwers lob a typical IJN depth charge? I haven't been able to find any information, photographic or otherwise, but am guessing 200 feet or so to each side of the ship?

Return (1): http://pwencycl.kgbudge.com/D/e/Depth_Charge.htm

“All Japanese depth charges had dimensions of 30.5" by 17.7" (77.5cm by 45cm). The Type 95 was standard at the time war broke out, with a 220 lb (100 kg) charge of Type 88 explosive (ammonium perchlorate and ferrosilicate). Its fuse had a water inlet that detonated the charge when a certain amount of water had entered. There were just two depth settings, 100 feet (30m) and 200 feet (60m).”

Return (2): http://www.ijnwarship.com/Anti-submarine/Anti-submarine%20-%20type%2094%20depth%20charge%20thrower%20a.htm

Return (3): http://en.wikipedia.org/wiki/Depth_charge

“In the Pacific, Japanese depth charge attacks initially proved fairly unsuccessful against U.S. and British submarines. Unless caught in shallow water, a U.S. submarine commander could normally dive to a deeper depth in order to escape destruction.

“The deficiencies of Japanese depth-charge tactics were revealed in a press conference held by U.S. Congressman Andrew J. May, a member of the House Military Affairs Committee who had visited the Pacific theater and received many intelligence and operational briefings. Incredibly, May mentioned the highly sensitive fact that American submarines had a high survivability rate because Japanese depth charges were fuzed to explode at too shallow a depth.

'“Various press associations sent this leaked news story over their wires, compounding the danger, and many newspapers (including one in Honolulu, Hawaii) published it. Soon, Japanese forces were resetting their depth charges to explode at a more effective average depth of 75 m (250 feet), to the detriment of American submariners. Vice AdmiralCharles A. Lockwood, commander of the U.S. submarine fleet in the Pacific, later estimated that May's revelation cost the United States Navy as many as ten submarines and 800 seamen killed in action.”