Other developments also continued. In 1958 a fusion warhead was developed and tested, the "UCRL Swift". It was 622 mm long, 127 mm diameter, and weighed 43.5 kg. At its test it yielded only 190 tons; it failed to achieve fusion and only the initial fission explosion worked correctly. There are unconfirmed reports that work on similar concepts continued into the 1970s and resulted in a one-kiloton warhead design for 5-inch (127 mm) naval gun rounds; these, however, were never deployed as operational weapons.