1) A one in twenty twist was required for the new design projectiles (see below) to be stable in flight, which accounts for the twist difference between the prototype and the production barrels.

2) During test firings in 1973 the sustained rate of fire was determined to be 11.7 to 12.6 rounds per minute.

3) The gun blast profile for this gun was established as being slightly less severe than that for an 8-inch bag gun.

1) The baseline shape of the new projectiles was 5.5 calibers in length with a one caliber boattail and had a discarding rotating band.  These projectiles were not completed at the time of the cancellation of the Mark 71 program.

2) In addition to the rounds listed above, there was also a Paveway or CLGP guided round.  This round had a special ramming sheath which was a modified cartridge case that supported the projectile, protected the fin assembly and provided a standard interface for the handing system.  Loading and firing of this round did require a double operation due to its longer length.

3) Ready service rounds were carried in a single drum containing 75 complete rounds.

4) The Mark 71 installation on USS Hull was restricted to the ready service magazine as no additional hull volume could be spared for further magazine capacity.  One version of the CSGN shows a magazine capacity of 400 rounds in addition to the ready service rounds.

5) The planned ammunition stowage for the Spruance class (DD-963) was as follows:

The first platform magazine (Fr. 77-94) held 129 ballistic projectiles, 119 standard propellant charges and 32 reduced charges.

The second platform magazine (Fr. 58-94) held 256 ballistic projectiles, 266 standard propellant charges, 40 Guided Projectile (GP) charges and 24 clearing charges.

The third platform magazine (Fr. 58-94) held 40 guided projectiles.

Including the ready service drum, the total ammunition stowage was 500 projectiles (ballistic and guided) and 556 propellant charges (standard, reduced, clearing and GP).

There have been many stories over the years about cracks in the structure of the USS Hull resulting from firing the Mark 71.  Most of these I would classify as "urban legends."

The Forest Sherman class ships were some of the first to be built with all-aluminum superstructures.  Beginning with the DD-937 [USS Davis], the ships were built with a higher bow to improve sea keeping in heavy weather.  [USS Hull] DD-945 and subsequent ships were built with a slightly different bow design.  These high bows are often referred to as “hurricane bows” and are the reason why DD-945 through DD-951 are sometimes referred to as the "Hull Class."  These high bows added significant weight to the forward part of the ship and placed additional stress on the superstructure.  Over time, all of these ships experienced cracks in the superstructure.  These cracks were generally located around frame 50 where the expansion joint was located in the hull.

When the ship modifications were being designed to permit installation of the Mark 71, special attention was given to the stresses that would result from the firing loads.  Later, during the structural firing tests, the Ships Engineering Center installed several hundred strain gages in the bow of the ship.  The data collected during these tests showed acceptable stress level in all locations.

When the Hull returned from her first WESTPAC deployment, I talked to the engineers doing the structure inspection.  They told me that the cracks they found were no different from what was found in every ship of the class.  They said the only difference was that the rate of cracking was slightly increased which was probably due the increased weight added to the bow by the Mark 71 installation.

It should be noted that all the ships built with aluminum superstructures experienced cracking.  This problem is still haunting the Navy.  Recently several of the CG-47 [Ticonderoga] class ships have had to be pulled from deployment in order to have their superstructures repaired.

I have never seen anything in official documents that reported or alluded to cracks in the hull.  This is the best explanation I can give for the stories about cracks.

CNO Project 186, consisting of ten Eight-Inch Unpowered SAL Guided Projectile firing tests from the USS Hull (DD-945) Mk 71 Major Caliber GP's (as well as 24 nonguided rounds, consisting of nine Ballistic Shapes and fifteen conventional rounds) were fired against shore and seaborne targets.  Two GP's were fired at a bunker target (MULE Laser - 13 KYD firing range), two at a stationary truck (MULE Laser - 13 KYD firing range), one at a moving tank (Spot Laser - 16 KYD firing range), and five at an ex-destroyer target HULK (13 to 16 KYD firing ranges).

The five hits on the target destroyer were with the 8-inch Paveway GP.  Actually, we were not supposed to sink the target, but the laser spot on the hull reflected down onto the water and one of the rounds hit low and put a hole below the water line, which meant that we were stuck with a slowly flooding target.  We had to pump about 50 rounds of 5-inch into the target before it finally sank.

1) The weight given above is only for the rotating gunhouse.  Not including ammunition, total weight was 224,471 lbs. (101,819 kg) including 32,611 lbs. (14,792 kg) below decks.

2) Standard manning was six enlisted men.

3) This weapon requires a stronger supporting foundation than that for the 5"/54 (12.7 cm) Mark 45 in order to accommodate the increased recoil forces.  Only the bow position on the Spruance class was strengthened to take this weapon, the stern position was not modified to support the larger gun.  As far as I have been able to determine, all Spruances were completed with the strengthened bow foundation.

4) Some of the early design alternatives for the DXG development program of the 1970s show a Mark 71 on the bow.  After the Mark 71 was cancelled in 1978, all new design alternatives for what ultimately became the Ticonderoga CG-47 class showed a 5"/54 (12.7 cm) Mark 45 in the bow position.  Like the Spruance class from which it was developed, the stern position for the Ticonderoga class was always planned for the Mark 45.

5) When Long Beach (CGN-9) was being considered for conversion to an Aegis cruiser during the 1970s, at least one proposal shows her with Mark 71 mountings on the bow and stern.

6) Plans for the canceled Strike Cruiser (CSGN) show one Mark 71 on the bow.

7) A study performed in 1991 by Gibbs and Cox showed that it was technically feasible to install a Mark 71 on a DDG-51 Flight I variant; however, the installation had some serious drawbacks.  The height of the required barbette caused the mount to restrict the view of the bow from the bridge.  This was considered to pose a safety issue when maneuvering the ship in congested waters.  In addition, the height of the mount would have imposed severe restrictions on the use of the forward VERTREP station.  This plus the cost and the small magazine size - 204 8-inch (20.3 cm) projectiles vs. 600 5-inch (12.7 cm) projectiles - caused the installation to be deemed undesirable.