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Originally Posted by brycelarson  yeah, I buy that.
think about low pressure this way - approximately the same number of air molecules need to reach the ball. The lower pressure the gas the larger the passage that needs to open to allow the same volume of uncompressed air to reach the breech of the gun. So, anywhere there's a restriction on the flow of gas will require a higher pressure to get the ball moving.
It's been a while since I've working on my Spyder clone - but basic idea is that you're going to need a valve that opens wider to run low pressure than high. This means you should look at the soft valve spring, any if you feel up to it, see if you can open up the passage through the valve after the cup seal - maybe you can get a bit more flow through there.
If you do achieve super low pressure the problem that you're going to run into is getting the gun to re-cock. Since the design uses the air pressure to return the bolt / hammer - at some point you'll turn it into a single action gun that you have to manually re-cock between shots. There's a thread somewhere on here about getting spyders to shoot at 177fps for use in Japan. Just reducing pressure was possible - but was goofing up the function of the gun. |
I've bored out an extra valve a bit to try to increase flow. Haven't tested it yet. Also modified a valve pin with an extra blow back slot to try to increase airflow to recock. I'll try combining those two along with the lighter valve spring and see what drive spring I can use. Thanks for the help.