The smallest diameter US test device publicly known was the UCRL Swift device fired in the Redwing Yuma shot on 28 May 1956 . It had a 5" (12.7 cm) diameter, a length of 62.2 cm (24.5 inches) and weighed 43.5 kg (96 lb). The test had a yield of 190 tons, but was intended to be fusion boosted (and thus would probably have had a yield in the kiloton range) but its yield was insufficient to ignite the fusion reaction and it failed to boost in this test. This test may have been a predecessor to the W-48 design.
В мае 56го в серии испытаний Redwing бабахнули устройство Swift, диаметр 5", длина порядка 24,5", мощность 190 т. Мощность оказалась недостаточной для приименения ТЯ-усиления (fusion boosting) с целью достижения мощности в килотонном диапазоне.