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    286 Discussions

    In the US, you don't need a 'gun license', because it doesn't exist. You need a 200$ tax stamp, and a Class III/II Weapons License to buy a silencer.

    Would a shorter barrel increase or decrease power? It would provide less friction on the ammo, but also provide less length for the pressure to push the ammo, so which would prevail?

    3 replies

    barrel length shouldnt "increase" power. it merely makes the energy more efficient. with a short barrel, the projectile gets out fast and the extra pressure will be ejected as well and just wasted. try measure your pressure in atm. it would roughly indicate how much it would expand. i.e. 2 atm will expand to 2 times the chamber volume.

    now V = Ad. and we know that the cross sectional area of the pipes are roughly same. so just use length instead of volume
    . i.e. 50 cm pipe for chamber at 3 atm shold expand to 150cm.

    chamber length + barrel length = final length of air
    50 + X = 150
    X = 100
    so no use of making the barrel longer than 100 cm.

    but remember that friction exists and the air cools off on expansion. so it wouldnt expand to 150 on the dot. so, instead of 100cm barrel, cut off some at the end

    hope im not wrong, but hope this could help

    For everything that has a barrel, there is a 'perfect length'. Where its at the point where its most efficient. If the barrel is too long it will lose momentum because the gas or air is expanding, but too short and it wont expand enough.

    Thanks for the amazing explanation (that wasn't sarcasm). It helps, and I think is is interesting how even the simplest types of math can be confusing with explanation (I first saw the math, and my jaw dropped, then looked more closely).

    If you put a t-angle on the barrel with a length of pipe and add a locking tire chuck with an air-compressor...could you make this semi auto? I am going to make this (my 4th airgun, 3 are ball valvers :D)
    p.s. put marbles in the t-angle?

    2 replies

    im going to use co2 instead, and then i can maybe make it semi, or possibly full even. make some marble mags.

    I gotta say that building this as only a 12 year old is quite impressive. Im only 16 and I am on an FRC robotics team (electrical subteam co-leader!) so i work with these kinds of things a lot. nevertheless, i love the fact that younger kids are getting into this kind of stuff. Kudos to u, good sir.

    Nope, no license needed. At least in the US, I remember just walking into big 5 when I was twelve and buying a high power rifle scope, they didn't say a thing except "Thanks come again".

    They are usually exactly the same, except that car valves are seperate pieces and bike valves are integral to the inner tube.

    Because the way they are designed makes it so it is a lot easier to release all of the air at once, where ball valves depend on user speed. The sprinkler valves allow more air out quicker thus resulting in a faster and more accurate shot. Also, its much less of a pain to squeeze a trigger than to rapidly twist a valve.

    I watched that video.

    Do I bloody like apples? That pained me.

    ...on a more serious note, excellent build.

    Excuse can somebody plzz tell me wat does "over under bit" mean on one of the pvc pipes when u hover your mouse over it???????!!!!!!!.............PLEASE REPLY I WANNA SHOOOT MANY MANY SQUIRELS