ORIGINAL: AW1Steve
It's not the weapon that subs should fear. It's the soviet tactics that were designed to use the weapon. The USSR kept depth charges , and short range mortars in production long after most of the western nations had abandoned them. That's because the Sov's had lots of small craft of little ASW (or any other kind of value). The theory was that if a western boat was found in a defended area , while the relatively usefull asw equipped vessels, helicopters and aircraft hassled and tried to localize the sub, they would bring every available vessel that could carry DC's or asw rockets and mortars as close to the area (what we'd call a datum, but the USSR wouldn't have anything that close) then they'd proceed with "mobbing tactics". They'd poor fire with every thing they had into the general area. Kind of a big (really BIG!) depth charge attack. Obviously it would completely screw up the water from a SONAR point of view, if the boat was unable to clear the area (think a diesel boat vice a USN/RN fast attack nuke) then the sub would at best have a very unpleasant surprise. And even a nuke , if the skipper were to be somewhat dim and NOT figure out what was coming his way could be hurt. (Even a blind squirrel occasionally finds a nut). It wasn't a brilliant or even particularly good tactic. But ya gotta use what you have. [:)]
Your last line has the most truth.
Look, we've both read the classified doctrine documents, even if some time ago. The Soviets never threw anything away. And their brass loved to write theoretical plans and procedures that were wonderful, on paper. They had a vast draft and thus almost no military labor costs, so yeah, they had a myriad of small coastal vessels, often WWII vintage and often with KGB crews, to putter around looking busy. They had DCs and RBU-1000s (-6000 only on corvettes and bigger.)
But they also have a vast coastline. And their ASW assets were clustered at ports like Vladivostok. Helos are great, but they don't live in fishing villages. And their very few helo-equipped skimmers were meat if they went out alone. Mobbing is a fine theory. They wrote about it endlessly. But it ignores size and space. It ignores that they weren't facing SSKs after the late-50s (when the RBU weapons were designed.) It ignores that Skipjack-class and 637-class SSNs could simply outrun almost all ASW skimmers in a stern chase, particularly if there were any sea state. And it REALLY ignores that their primary problem, still unaddressed when the USSR fell, was primary ID of a penetrating SSN. They simply didn't know ours were there. There's a good reason no member of USS Parche's crew ever has to buy their own drinks. I'm sure you have, as I have, discussed northern spec ops with that era's crews. A lot of the best ops were nowhere near Soviet centers of ASW power. They just weren't worried about RBUs. Helos and Bears? If they got into the zone they were no fun. But a Grisha with an RBU? Please.
In blue water RBUs are even dumber. Engagement ranges are 20-30 miles in unclassified sources. A sub's FC party could go have a sit-down meal during the run-in time of a Mk 37 or Mk 48. Folks just don't get what a massive change there was in anti-surface submarine ops after 1960. Any ship with an RBU was going to die, or be running for its life, long before it got to even a fraction of 1000-yards of an SSN. Before it knew there was an SSN around. (Or two. Or three.) RBUs were weapons designed and fielded just as their usefulness against DE subs was disappearing. Better plate armor against gunpowder.