The "special armament" designation may confuse some. All P2V-3B Neptune versions were previously P2V-3C versions, which were the first USN aircraft carrier-launchable atom bombers in the early Cold War days, in USN Heavy Attack Composite Squadron VC-5.
Once the AJ-1/2 Savage aircraft became operational in VC squadrons VC-5,6,7,8 and 9, the P2V-3C Neptunes were modified by installing the AN/ASB-1a Bomb Director System (which was in the AJ Savages, and later in the A3D Skywarriors of Heavy Attack Squadrons designated VAH).
The P2V-3B aircraft went to Heavy Attack Training Units (HATU) for in-flight crew training with and AN/ASB-1a system.
The P2V-3C/3B aircraft also had tailhooks and while no aircraft carrier landings were accomplished, such arrested landings (traps) were done at NAS Patuxent River, and at small airfields in the Mediterranean area on special missions, staging from NAS Port Lyautey, FM in the early 1950's.
Please see:
P2V-3B and P2V-3C NEPTUNES
http://community.webtv.net/cerebralhush/USNavyHeavyAttack/page3.html
P2V NEPTUNES ASSIGNED TO VC SQUADRONS
http://community.webtv.net/cerebralhush/USNavyHeavyAttack/page5.html