how far the piston must open?

[far_cry]

i am almost finish my co-axial rifle
the barrel is 10mm (outside) and a 8 mm bore, the chamber is 3/4" steel pipe he had 2cm diameter inside.
how much the piston must open far away from the barrel when release the air?

[Mr.Sandman]

looks like it will be fine but your piston doesnt need to move that much but how long is your piston?

[mark.f]

For a barrel with an I.D. of 8mm I would suggest 2 millimeters.

[far_cry]

looks like it will be fine but your piston doesnt need to move that much but how long is your piston?

i have to build it soon ,i think about 1 to 1.5 cm
and i think about 1 cm gap

[jook13]

They say that a good rule of thumb is to have the piston travel be at around 1/4 of the barrel diameter... I usualy go with a tad more, just to be safe.

[Velocity]

For a barrel with an I.D. of 8mm I would suggest 2 millimeters.

I agree. However, just in case, you might want to bump it up to 3mm, to make sure you are not choking flow.

[far_cry]

thank you fellas that's will help me a lot
just in case what if i make the gap 1 cm instead 2 mm ??

[daberno123]

just in case what if i make the gap 1 cm instead 2 mm ??

More flow, but 1 cm is way overkill and all it will do is add to your pilot volume, therefor reducing overall performance. Do what Mark and Velocity said and aim for 2-3 mm.

[Sticky_Tape]

You will ALSO be exspanding the air in your chamber making the gun less powerful. Once the piston opens past 1/4 the barrel i.d. then you are just exspanding air into the extra area but it wouldn't make much of a difference.

[far_cry]

roger comrades

[jackssmirkingrevenge]

>>Some thoughts on the subject<<

[ALIHISGREAT]

personally i would aim for 5mm

[BlackH]

I think 5mm too

[far_cry]

ok i will try thanks