Inside the Gun

                                                                                                                                                                            The mechanics of a paintball gun are pretty simple. Initially the user cocks the bolt                                                                                                                                into place, this compresses a spring. When the trigger is pulled the bolt will be                                                                                                                                        thrown forward do to the spring force. The bolt will collide with a pin connected to a                                                                                                                            valve that holds back the compressed gas. The gas will then be released into the                                                                                                                                    barrel and contact the ball. The compressed will gas expand creating a force on all the                                                                                                                            surfaces around it. The ball now inside the barrel is only blocked from rolling out by                                                                                                                                the friction of the barrel and the force of the gas being much much greater then this                                                                                                                                friction the ball is expelled out of the barrel at great speed.

                                               (Spyder Animation courtesy of

Lets Look at the Physics

The initial release of gas is controlled by how long that valve can remain open. That valve has its own spring inside it to re-close after the bolt is reset.
So the more Force that can be delivered to the valve wider the value can open

Spring Force


F=Spring Force, k=Spring Constant, X=Compressed Distance, Xo=Initial Distance

If the positive Axis is down the barrel then X is less then Xo making this force in the positive direction
since the mechanics of the gun require a trigger latch and the valve distance cannot be changed this leaves only one variable
the value of k can be changed by replacing the spring with one of the same dimensions but stiffer.
Manufactures sell spring kits for this reason, older guns with more friction in the bolt slide need stiffer springs to open the valve.

The spring is trying to do Work on the valve. It applies a force through the small distance that the valve requires to open.
While this is happening Friction in bolt slide is creating negative work on the bolt.
This work done by friction is in the opposite direction of the spring work which decrease the amount of work done to the valve.

Friction Force

F=μ (N)

F=Friction Force,
μ=coefficient of Friction, N=Normal Force

Friction always opposes motion, here the bolt is moving in the positive direction because the spring force is positive.
Frictional force is then in the negative direction. If the goal is to increase the performance of the marker then there is two variables
The coefficient of friction can be lessened by lubricant. Also the Normal force between the bolt and slide can be lessened by replacing
the bolt with a lighter version.

Work done to the Valve

The amount of distance the valve covers is limited by the dimensions of the marker, meaning at some point no more work can be done to the valve.
To ensure your marker reaches that point these equations will benefit you.

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