Here is a couple of suggestions sent in by fans.

I take no responsiblilty if a spring pokes out your eyeball.



To add extra power with springs

From invisiblelight386:



first unscrew both guns. take the spring out of one of them. now take the other gun and remove the plunger, toob thing and the barrel that holdes the darts. the plunger should already have a spring on it. remove the trigger lock on the plunger and slide the other spring on put the lock back on (this might take a wile). when the spring and the lock are on insert the plunger back into the toob. reassemble the gun leaving out the dart barrel. now take a bic pen and remove the ink. cut off the top black stopper. spray DW40 or any other silicon lubricant into the pen. pinch one end of the pen and insert in to the ovle thing at the end of the toob. now there are two things you can do: 1. fill the front of the gun with expandable foam. this will hold the pen in place and muffle the sound. cover the front with duck tape. to fire insert the bb then cock it (the first couple times it wont go very far because of the lubricant). you can take a very smal pice of cotton and stick it into the barrel to dry out the lubricant.



also the more springs you put in weakens the trigger lock and can fire unexpectedly. so becarful. i shot myself to test how much it hurts from 5 feet away and it inloged into my hand. THIS IS VERY POWER FULL.



Heres a good idea from KnextGeneration:

To increase accuracy of bullets, enlongate the barrel. This is true for all guns. For pen barrel guns though, it is hard to line up 2 pen barrels right next to each other without one aiming in a different direction then the other.

KnextGeneration's idea was to take a pen grip, the rubbery things you put on pencils or pens to make the grip more confortable, and put half of it on one end of a pen, and half on the other. This way, you know that they are aligned. You may want to tape both ends of the grip on the pens, and maybe add a long knex piece for strength. Before long, Youll be making sniper rifles. If only pen guns and shoot at 1000 fps. sorry, daydreaming. anyway thanks for the tip, and good luck on making these.



There were also some questions about measuring fps. theres basically 2 ways to do by yourself.



1. Get a friend to get a stopwatch. Shoot your gun at a target 20 feet away, to give you friend a chance and starting and stopping the stopwatch at the right time. Take how long it takes, for example .25 seconds. Take 20 feet divided by .25 seconds. 20 divided by .25 is 80. that means the bullet traveles at 80 fps.



2. Get a gun you know the fps of, like a friends airsoft gun. Shoot that at a wall far away and time how long it takes. Then shoot the homeade one. If they are the same, they have the same fps. If it take the real airsoft gun a short time, the homeade one is less. If it takes more, well, you get the picture.

You can also shoot a real airsoft gun at a piece of styrofoam from about a foot away, and then shoot your homeade airsoft gun at it the same distance away. Use and exacto knife to cut the styrofoam down the side and find the bullets.



example: if a 300 fps airsoft gun shoot in 10 inches, and you shoot your gun and it goes 5 inches, your gun probably shoots around 150 fps.



hope this helps. -Perjak