The Ontos was designed as a family of infantry vehicles, the first two built were the T55 and and longer-hulled
T56 personnel carriers (6 and 10 troops respectively). The production M50 six-rifle anti-tank version was based
on the T55 hulled T165E2 developmental vehicle, all SP developments were T55 based. The T166 mounted one
rifle on a hydraulically operated version of the ground mount, four-rifle T164 and eight-rifle T167 variants were
proposed but never built.
Titanium hulled single and twin-turret assault vehicles were also planned, along with heavier anti-tank vehicles
using Ontos family components. Project AT-2 used the hull of the 90mm T101 aka M56 Scorpion/SPAT.
from Hunnicutt - Sheridan.