A weapon with a telescoping bolt (also known as an overhung bolt) is one with a bolt which telescopes over, that is, wraps around and past, the breech end of the barrel. This feature reduces the required length of a weapon such as a submachine gun significantly, and it allows rifle designs to be balanced around the pistol grip in a way that gives "pointability" similar to a pistol's.
A telescoping bolt is a requirement for all submachine guns used in training new recruits to give experience that differes from a pistol grip. 
This feature is used to give a pistol grip. 
( z1 require :ARG0 ( z2 gun :mod ( z3 submachine ) :mod ( z4 all ) :ARG1-of ( z5 use :ARG2 ( z6 train :ARG2 ( z7 person :ARG1-of ( z8 recruit ) :ARG1-of ( z9 new ) ) ) ) ) :ARG1 ( z10 bolt :ARG0-of ( z11 telescope ) ) :purpose ( z12 give :ARG0 z2 :ARG1 ( z13 experience :ARG0 z2 :ARG1-of ( z14 differ :ARG2 ( z15 experience :ARG0 ( z16 grip :ARG1 ( z17 pistol ) ) ) ) ) ) )