A pneumatic sealant gun comprising: a sealant gun valve body, configured to fluidly couple with a compressed or pressurized source of gas or air, the sealant gun valve body including a valve-controlling mechanism configured for selectively blocking or allowing the gas or air out of the sealant gun valve body; a hollow sleeve having a first opening and a second opening opposite the first opening, wherein the hollow sleeve is fluidly coupled with the sealant gun valve body via the first opening of the hollow sleeve; a sealant tube configured to fit within the hollow sleeve and to contain sealant therein, wherein the sealant tube has a first opening, a second opening opposite the first opening, and one or more pressure release openings located between the first opening of the tube body and a plunger wherein the sealant tube is fluidly coupled with the sealant gun valve body at the first opening of the sealant tube such that gas or air can flow from the compressed or pressurized source into the sealant tube and between the sealant tube and the hollow sleeve, thereby equalizing pressure on an inner surface and an outer surface of the sealant tube; wherein the sealant tube includes an engagement portion extending therefrom, sandwiched between the sealant gun valve body of the pneumatic sealant gun and the hollow sleeve of the pneumatic sealant gun; said plunger configured to fit in slidable contact within the sealant tube and configured to be pressed toward the second opening of the sealant tube when gas or air flows through the sealant gun valve body; and a seal or gasket proximate the second opening of the hollow sleeve, forming an airtight seal between the hollow sleeve and the inner sealant tube. a sealant gun valve body, configured to fluidly couple with a compressed or pressurized source of gas or air, the sealant gun valve body including a valve-controlling mechanism configured for selectively blocking or allowing the gas or air out of the sealant gun valve body; a hollow sleeve having a first opening and a second opening opposite the first opening, wherein the hollow sleeve is fluidly coupled with the sealant gun valve body via the first opening of the hollow sleeve; a sealant tube configured to fit within the hollow sleeve and to contain sealant therein, wherein the sealant tube has a first opening, a second opening opposite the first opening, and one or more pressure release openings located between the first opening of the tube body and a plunger wherein the sealant tube is fluidly coupled with the sealant gun valve body at the first opening of the sealant tube such that gas or air can flow from the compressed or pressurized source into the sealant tube and between the sealant tube and the hollow sleeve, thereby equalizing pressure on an inner surface and an outer surface of the sealant tube; wherein the sealant tube includes an engagement portion extending therefrom, sandwiched between the sealant gun valve body of the pneumatic sealant gun and the hollow sleeve of the pneumatic sealant gun; said plunger configured to fit in slidable contact within the sealant tube and configured to be pressed toward the second opening of the sealant tube when gas or air flows through the sealant gun valve body; and a seal or gasket proximate the second opening of the hollow sleeve, forming an airtight seal between the hollow sleeve and the inner sealant tube.