Rarefied air! This airsoft AK-47 has been hot-rodded with an adjustable buttstock, internal hop-up gearbox, slick Aimpoint scope and Picatinny-railed forend. Hiro Soga Photo

From the very creation of weapons, their users have sought to modify them. You know there was a Neolithic man who thought sticking some feathers on the back of his spear would improve his chance of bringing home some meat. And made it look cool. When it comes to modern airsoft guns, an entire industry of aftermarket spring, piston, and gear manufacturers has sprung up to wring the most performance out of these 6mm plastic BB firing arms.

While hot-rodding your Airsoft gun’s performance is generally called “hopping up,” “hop up” specifically refers to an adjustment in the gun’s gearbox that puts a backspin on the pellet as it heads down the barrel. Since gravity starts working on your projectile as soon as it leaves the muzzle, one of the keys to accurately firing a centerfire rifle or an airsoft rifle is getting the projectile or bullet to fly as straight as you can for as long as possible. Centerfire rifles do this with the proper spin and powder charge to increase velocity and range. Airsoft guns use the hop-up’s backspin on the BB to cause it to rise upward as they are fired, extending the time before gravity pulls it to the ground.

Watch Your Speed
The hop-up adjustment also allows the shooter to raise or lower the feet per second (FPS) achieved by their weapon’s ammunition. Why would you want to lower your velocity? Well, public airsoft ranges have FPS limits to keep injuries down. Outdoor ranges usually have a limit of 400 FPS, while indoor ranges top out at 350. Shooters will have to fire their weapons through a chronograph screen to ensure they are not over the limit. Since airsoft rifles will come “out of the box” with velocities ranging between 360 and 415 FPS, they will need adjustment to be legal at these ranges.

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Rarefied air! This airsoft AK-47 has been hot-rodded with an adjustable buttstock, internal hop-up…