now referring to fig8 of the present invention the flange 150 has been eliminated and a connection is made directly between the outer surface 141 of the outer casing tube 140 and the interior surface 91 of the breach block housing 90 by this arrangement the constriction 152 is eliminated and area 156 defining the open space at the location of the connection between the breach and barrel has a size at least as large as the annular space 146 between the barrel tubes 140 and 142 therefore the annular space 146 within the barrel is able to more quickly evacuate creating greater initial pressure within the cavity 134 this greater pressure achieved within the cavity causes the soil nail to be propelled at a faster rate through the barrel the user therefore has the option of either providing less pressure within the annular space 146 to achieve adequate penetration or may achieve greater penetration of the soil nail with the same applied pressure as compared to the prior art by redesigning the connection between the breach and the barrel improved air flow is achieved which allows a more immediate evacuation of the compressed gas into the breach chamber thereby increasing the.