Forum rule nr 1.
Not nr.2...
1!
Don't be a jerk.
Keep the flaming to a minimum. Remember, you were a noob once too. Also, keep in mind that this is a text-based medium, and as such, sarcasm does not always translate well.
Boys!
Behave yourselves.
now..
Hi, i'm new relatively new to this but I'm planning to build a QEV or pistonvalve airgun with a hammer valve as the pilot, allowing semi-auto firing. Any suggestions on chamber volume ( i'll use 1/2 inch copper barrel) or general help will be greatly appreciated
Small chamber volume would give you very few shots and pressuredrop between shots is drastic.
No matter what pressure you intend to use a basic principle is that for multishot you want as much volume as possible.
Only you can decide how much is too much.
I like both performance and looks so I generally go as big as possible without making it look bulky.
Using high pressure allows you to get powerful multishots from a relatively small package.
But size still matters at high pressure.
The bigger, the better.
Big means better power and less dramatic pressuredrop.
Now another thing that comes into play with a hammered QEV:
The pilot can be used to tune the powerlevel.
A strong hammerspring and heavy hammer give what I like to call "deep"shots, the reverse will give you "shallow"shots.
The amount of gas expelled by the QEV is closely related to the pilotvalve settings in this kind of setup.
The very size of the hammervalve also makes a difference.
All this makes it very hard to give an exact answer to your question.
Leaving out the information on pressure, barrellength, ammo, personal taste and last but not least your expectations on performance makes it downright impossible.
Hope this helps.
welcome to the forum!
