There are two principal autofrettage processes. One is ‘‘hydrostatic,’’
based on the use of high hydrostatic pressure that is applied
inside the tube and the second is ‘‘swaging,’’ which is based
on the use of an oversized mandrel forced through the tube bore,
thereby causing it to expand.
The residual stresses, which have a compressive effect on the
internal barrel surface, increase the barrel elastic strength pressure
and slow down the development of cracks. Furthermore, it is
sometimes necessary to machine the barrel to its final dimensions,
which reduces the contribution of residual stresses.