by B.B. Pelletier
The Gamo PT-85 Blowback Tactical air pistol is a different air pistol in several ways that I will describe to you today. For starters, the most dramatic difference that strikes me is this pistol has a 12-inch barrel! You read that correctly, a 12-inch barrel. So, when Gamo makes the claim of being the fastest CO2 pellet pistol around, they have done their homework to make it so. The extra-long barrel means additional “burn” time to the gas, which is really extra acceleration time in the barrel. Carbon dioxide is a relatively sluggish gas that needs a longer time to act on the base of the pellet because of its lower pressure. With just 850 psi at 70 degrees F, it has about one-half or less the pressure of air found in a precharged pneumatic gun, plus the large CO2 molecule moves more slowly through the valve than the much smaller atoms found in air. In recent testing reported on the internet, a barrel length of 16 inches was found to be about optimum for CO2, as far as terminal velocity is concerned. That was with the valve in the gun that was being tested, but the valve in the PT85 pistol is certainly in the same class.