Coast Guard photograph, PHC Ken Mather, USCGC Sherman (WHEC-720) in her original configuration with a 5″/38 and dual hedgehogs, April 1969.
This is hardly a current topic, but it is one I have seen discussed several time, most recently in comments on a post about the new Canadian Arctic/Offshore Patrol Ship (AOPS), e.g. why the Coast Guard used the 76mm Mk75 gun on the 378 FRAMs rather than the 5″/54 Mk45.
It is true that, although about four tons heavier, the early model 5″/54 Mk45 mounts were a drop in replacement for the 5″/38 mounts we had on the 378s. It would have appeared an easy choice, but in order to accommodate the additional weight of the Harpoons and CIWS, perhaps the Coast Guard had no choice but to go with a lighter gun. That gun (and its associated firecontrol system) was certainly seen as a significant improvement over what we had had in essentially all respects including reduced manning and maintenance.
If we look at the weights as built that were removed:
one 5″/38 (20.5 tons) and two hedgehogs (14.4 tons), totalling approximately 35 tons
and compare that to some of the weights added
one 76 mm Mk75 gun (8.2 tons), two Mk141 quad harpoon launchers (11.8 tons total), eight Harpoon (6 tons), and a Mk 15 Phalanx CIWS (6.8 tons). Total approximately 32.8 tons. Plus more weight for the addition of the hangar. Essentially the difference was a wash.
If instead, we had used the 5″/54 Mk45 mod 0 (24.5 tons) in addition to the harpoons and CIWS, the total weight would have been 16.3 tons higher or 49.1 tons.
There are other weights that might be added in calculating the total weight devoted to armaments, but obviously I don’t think this was an excessive amount, there are too many examples of smaller ships with far more weapons. I previously noted, (“OPC-Design for Wartime, Build for Peacetime”) that as built the little 255s had 140 to 150 tons of weapons.
Even so, an additional 16.3 tons topside (even if that is only about 0.5% of the full load displacement) might have been too much for the 378s. I don’t know. Perhaps a former 378 engineer or DCA could enlighten the discussion.
Photo: Navy photo, USCGC Mellon, with 76mm, Harpoon, and Phalanx CIWS
Chuck Hill's CG Blog 
How many tons of ballast had to added to make up for the lighter weight of the 76mm? In addition, the ammunition for the 5″/38 came in at 55 pounds a projectile and 32 pounds a powder case. The total weight of the Mk30 5″/38 was 25 tons that included the projectile hoist that was nearly all bronze.
The 311 originally had two closed 5″/38s forward and two open mounts aft. See the Coos Bay in 1943 http://www.history.navy.mil/photos/images/n40000/n47253.jpg and Unimak in 1944 http://www.history.navy.mil/photos/images/n60000/n61152.jpg
The forward magazines could hold over 1500 rounds (powder and projectile). Unimak had 200 tons of ballast in the bilges of the forward magazines to compensate for the removal of mount 52.
The reason the Coast Guard went with the 76mm was because the Gunner doing the selection was a FT. He really liked computers but not guns so much.
When did they take the Hedgehogs off? They were not on my 378′, w/ 5″/38 mount in 1987.
I only recall two 20mm weapon mounts up forward of the CO’s cabin. (what was that area called – Captains Bridge/deck/????)
I don’t remember exactly when the Hedgehogs were removed from the 378s, but it was probably when they removed the ASW equipment (hedgehogs, sonar, and torpedo tubes) from the older WHECs (327s, 311s, 255s). That happened 1970/71 (I believe). At one point, I think the 378s mounted the over and under .50 cal and 81mm mortar in place of the hedghogs on the O-1 deck forward of the bridge.
It would be interesting to know the reasoning being the removal of the the Hedgehogs from the 378’s.
I readily admit I don’t understand ASW but one would AssUMe that the Hedgehog should have been integrated with the other parts of a total ASW weapon system (i.e. Sonar and Torpedo’s).
My 378 still had sonar and the Mark-32 three-torpedo launcher in 1987-89…as well as another item we trailed behind us (some sort of noise maker I believe someone told me – to distract an incoming torpedo!) 😮
We shot a practice torpedo or two off of Kauai – I still have pics that I need to figure out how to post and link!
The hedgehogs were probably removed because they were very short range weapons, and by the 70s, getting that close to a sub was very dangerous.
http://en.wikipedia.org/wiki/Hedgehog_(weapon)
The noise maker was “NIXIE” intended to distract acoustic homing torpedoes
IRT the 311’s, how many were assigned to those cutters? With four 5″ mounts, that’s a LOT of personnel assigned at GQ – who’s left for the repair lockers and other GQ watch-bill stations?
😉
In Coast Guard service the 311s never had more than one 5″/38 (and a twin 40mm), Even in Navy service during WWII installations varied. http://en.wikipedia.org/wiki/Barnegat_class_small_seaplane_tender
The 270s, being built just before and during the 378 FRAM were built with the Mk75 76mm gun and Mk92 Fire Control. If you are going to have 13 systems on 270s, why not expand to have 25 and simply training, refurbishment and spares?
The FFG7 class, also being built before and during the 378 FRAM has the same basic system (the Mk92 Fire Control on a FFG has more features). Again, going to the 76mm allowed the Coast Guard to leverage a Navy program of record.
Having served on pre and post FRAM 378s, I would have preferred a 5 inch gun and a few extra weeks in San Diego conducting naval gunfire support.
Sorry you sill not get weeks more in San Diego. Maybe a couple of days. When the 378s had 5″ we did do shore bombardment at San Clemente. Refresher Training was four weeks, but we were also doing ASW.
Pre Fram on RUSH, the CIC team got a week of NGFS team training, a week each of ASW Phase I & II, a week of Target Motion Analysis team training, a week each of Intermediate & Advanced Multi Threat team training. After FRAM, the ASW and NGFS dropped off of course, but we added a week for Harpoon. All in all, better to be in San Diego on per diem than on the quarterdeck for the 4-8 watch. Or so it seemed.
Ah, you are talking about CIC team training in addition to Refresher Training. Why Target Motion Analysis training “pre-FRAM” on a ship that had neither a towed array or Harpoon?
I’m still thinking the 76mm is the best combination of light weight, “punch” (please no jokes from you 5″ advocates 🙂 ), and flexibility (NGFS, Anti-ship, & anti-missile/aircraft). It’s a shame we couldn’t get the light weight & firepower of the modern Oto-Melera Super-Rapid with the reliability of the Bofors. (It’s a shame the US doesn’t make things any more or we probably could…)