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Model48 (no login)
Posted Jul 1, 2009 8:25 PM
You leave out one important variable in your force per unit area analysis:
The TOTAL potential energy in the system (the compressed spring) is the same regardless of caliber.
As the spring releases this energy, it builds pressure in front of the pision, which acts on the area of the pellet (or bore diameter)and truely, for a larger diameter a greater force is applied.
However - for every force, there is an equal and opposite force. And a .22 caliber pellet weighs more than a .177. By nature of it being heavier, it provides more resistance to the pressure (opposing force) developed by the piston.
In your example, for a given spring/piston arrangement that develops a consistent pressure when released, regardless of caliber, a .22 cal pellet, given its larger diameter, would exit the barrel FASTER than a .177 due to the large force applied to it. Except for the fact that a .22 weighs more and takes more force to get moving. Ironically, all .177/.22 guns deliver lower velocity in .22 than .177.
Now, having read that "heavy pellets damage spring guns" so many times, I'm going to have to do some math (ugh!). The reasons being: 1)I respect Hector's experience (and others) that heavy pellets decrease spring life and are in fact "harder" on spring guns; 2) Given a fixed amount of potential energy for a cocked spring, there should be a mathmatical relationship between velocity, pellet weight, and pellet diameter. The fact that (generally) a given airgun model delivers (relatively) the same energy (as measured in ft-lbs based on pellet velocity) regardless of caliber, tends to follow the laws of physics.
What is lacking in my analysis is the energy lost engery due to friction, etc and any differences of lost energy between calibers. There's also some dymanics issues bound to be in this equation(which is not my strong point,) perhaps that are related to the rate at which pressure developes behind a .177 and .22 cal pellet....
Anyway, its an interesting topic that I'm going to spend some time with.
Good shooting to all and no disrespect to Hector who is a treasure chest of knowledge here at the Dianawerk Collective!
Model48
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