Knob Creek '13: Hedgehog Anti-submarine round

200$ to cover the NFA stamp and 90 for the shell itself? would this be a DD?

The Hedgehog Anti-Submarine Projector was developed by the Directorate Of Miscellaneous Weapons Development for the Royal Navy early in World War Two. It was officially accepted for general service in corvettes, frigates, destroyers and other dedicated anti-submarine vessels in 1942 and was intended to supplement conventional depth charges. Each individual Hedgehog was actually a very simple, low-cost navalized 7.2" spigot mortar round designed specifically to detonate only on direct contact with a target, and was not fitted with a hydrostatic pistol, a magnetic pistol or any of the actuation devices one would normally associate with proximity detonation of a depth charge or torpedo. Instead, the Hedgehog was launched in multi-projectile salvos into the general vicinity of the target submarine ( as determined by echo-sounding, i.e., sonar detection ), and depended largely on this "spread" to achieve significant hit probability, much like a shotgun firing 00 buckshot. While the explosive charge was relatively small compared to a depth charge ( which typically would be a 300-lb. device in the "light" version, or a 600-lb. device in the "standard" or full-sized version ), it was sufficiently powerful to severely damage or breach the pressure hull of a U-Boat and cripple or sink her if a direct hit was scored.

This "scattergun" approach using the Hedgehog A/S Projector was highly successful, and soon Allied vessels, including those of the United States Navy, were similarly equipped. Over time, Hedgehog was supplemented or replaced in RN service by more sophisticated derivatives such as the Squid and Limbo A/S mortar systems ; the U.S. Navy continued with its own developmental line and came up with the Mousetrap and Weapon Alpha systems. Mousetrap was either a 4-railed ( Anti-Submarine Projector Mk.20 ) or 8-railed ( Anti-Submarine Projector Mk.22 ) device that could fire Hedgehog projectiles fitted with 2.25" Mk.3 solid-propellant rocket motors. This modification enabled smaller, lighter ASW vessels, such as sub-chasers, to take advantage of the benefits of the multiple projectile launch system without the risk of structural or hull damage from the considerable recoil of the original Hedgehog mortar system. Mousetrap was designed and developed in a relatively short period of time ( thanks to the pressures of war ) by the euphemistically-named National Defence Research Committee at CalTech beginning in late 1941.