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Dag Evert's "American Classic"

As mentioned on the forum, heres a picture I took some time back, with natural winter daylight. A 2100, and a 1377, both guns have been recrowned, and had their trigger parts shimmed for play, contact surfaces stoned, and trigger springs somewhat reduced within safe limits. The 2100 has had its barrel shimmed with tape to remove play.
Both guns give great accuracy for the money if they are given good pellets!
The combination of pellets and guns in the picture represents something close to my boyhood dreams:-)


-- Dag Evert

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Gas velocity - port hogging relationship

June 29 2012 at 8:23 PM
Airfierce  (Login Airfierce)
Crosman Forum Member
from IP address 66.81.28.107

I don't have much experience with airgun mods, also haven't been on the forums for quite a while.

I got to wondering about opening up ports. Seems that where you have a large volume chamber and a small orifice for air to pass through on its way to being exhausted, the restriction would work under the venturi effect. This would cause the gas to speed up exponentially at point of restriction, effectively causing a ram induction force into exhaust, increasing volume more quickly and speeding gas flow.

If that transfer port or whatever is opened up then there would be a loss of venturi effect and loss of gas velocity. Has any research or data crunching been done regarding this, to show where an intended improvement actually causes a net loss in pressure or gas velocity behind pellet? I can see advantage to smoothing contours or sharp edges however it seems there's a danger of backpedaling when hogging ports. Apologies if this has already been over thunk and discussed ad infinitum...

 
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