Though unconventional, the Jackhammer can best be described as a gas-operated revolver.
Many parts were constructed of Rynite polymer to reduce weight.
Layout was of a bullpup configuration with a 10-round revolving cylinder that fired conventional, 12-gauge shells.
The cylinder's method of rotation was very similar to the Webley–Fosbery Automatic Revolver, an operating rod being used to rotate the cylinder.

The Jackhammer is capable of semi-automatic and fully automatic fire by way of a thumb safety/selector switch.
 At the moment of firing, the front of the shell sealed inside the breech of the barrel much like the Nagant M1895 revolver.
 Unlike the Nagant, whose cylinder moved forward to form the seal, the barrel of the Jackhammer was driven forward and away from the cylinder by a ring-piston, using gas tapped from the bore.
 As the barrel moved forward, the breech cleared the front of the fired cartridge and an operating rod attached to the barrel rotated the cylinder through a "zig-zag" cam arrangement.
As the next shell aligned with the bore, the barrel returned under spring pressure back into the front end of the cylinder.
 Spent shells were retained in the cylinder, as in a traditional revolver.
 The Jackhammer has a charging handle in the forward grip to charge the weapon and a cocking lever in the buttstock to recock the firing mechanism in case of light strikes to the primer.
 For reloading, the cylinder was removed from the bottom of its housing and shells were manually extracted.
Removing the cylinder required the barrel be moved and secured in the forward position.
Though unconventional, the Jackhammer can best be described as a gas-operated revolver. Many parts were constructed of Rynite polymer to reduce weight. Layout was of a bullpup configuration with a 10-round revolving cylinder that fired conventional, 12-gauge shells. The cylinder's method of rotation was very similar to the Webley–Fosbery Automatic Revolver, an operating rod being used to rotate the cylinder.
The Jackhammer is capable of semi-automatic and fully automatic fire by way of a thumb safety/selector switch.  At the moment of firing, the front of the shell sealed inside the breech of the barrel much like the Nagant M1895 revolver.  Unlike the Nagant, whose cylinder moved forward to form the seal, the barrel of the Jackhammer was driven forward and away from the cylinder by a ring-piston, using gas tapped from the bore.  As the barrel moved forward, the breech cleared the front of the fired cartridge and an operating rod attached to the barrel rotated the cylinder through a "zig-zag" cam arrangement. As the next shell aligned with the bore, the barrel returned under spring pressure back into the front end of the cylinder.  Spent shells were retained in the cylinder, as in a traditional revolver.  The Jackhammer has a charging handle in the forward grip to charge the weapon and a cocking lever in the buttstock to recock the firing mechanism in case of light strikes to the primer.  For reloading, the cylinder was removed from the bottom of its housing and shells were manually extracted. Removing the cylinder required the barrel be moved and secured in the forward position.
Pancor Jackhammer