QEV + slide valve multi shot - HELP!

[encohen]

Hey,

I'm new to airguns and I've decided to build one.
I'm still testing for an effective setup, and was hoping you can help.

My first version was a 500cc soda stream air reservoir with a 1\2" ball valve (powered by a spring) and a 1\2", 38" long galvanised steel tube as a barrel. it was a single shot and it was really powerful. it could completely penetrate a 1" plywood from 15 meters shooting 100 grains nail dart at 160 PSI.

it was nice, but i wanted to upgrade it and get multi shots per fill, so i got a QEV and slide valve and connected them to the same barrel and air reservoir, as shown here:

so i get more shots per fill now, but the power has decreased dramatically, the same nail dart does not penetrate the plywood.

volumes:
air reservoir: 500cc
firing chamber: 50cc
barrel: 120 cc
--------------------------------------------------------
so after doing some reading in this forum i have come to understand i need to make some changes.
I think these are my options:

1. increasing firing chamber volume
2. decreasing barrel volume
3. increasing air pressure (got a new shock pump - 600 PSI)

which will make the most impact?
it there any better options?

Thanks

[jackssmirkingrevenge]

The best idea is to first download GGDT:

http://www.thehalls-in-bfe.com/GGDT/

This excellent program will allow you to virtually model the parameters (chamber volume, pressure, barrel length etc.) to give you a very good idea of what will give you optimal performance.

Higher pressure is definitely the parameter that will give you the biggest boost. Also reducing your barrel length will almost always reduce performance unless you have a really tiny firing chamber or are using extremely low pressure.

(got a new shock pump - 600 PSI)

It will take you forever to pressurize that size of bottle to 600 psi with a shock pump, consider a fridge compressor:

http://www.spudfiles.com/how-to-databas ... 11866.html

[encohen]

That's what i came up with

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