Barrel/cylinder ratio - sorry for yet another thread

[Ianbuckwell]

If using a 150psi, iirc the barrel to cylinder ratio should be about 1:1, do you just use this figure or add say a 10% gain to the cylinder just to ensure your projectile gets at least enough air??? I guess it can't do any harm apart from waste a bit of air.

Was given the idea of an old fridge compressor by Smirkjacksrevenge, so if I can get one of these air over 150psi won't be a problem, as it sounds like shock pumps are a lot of hard work, especially if you have around 1 litre (sorry don't know it in cubic inches) primary tank. Just need to find an old fridge

[Gippeto]

Model it with ggdt. Swap variables for performance until you're happy....then build to that "spec".

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

[Ianbuckwell]

Only have access via phone and Nexus 7 have to go see my mum and use her computers, are there any instructions around as i will be have a lot more questions, i am sure!!

[jackssmirkingrevenge]

To answer your PM in public so others may benefit:

Shock pumps are a real pain in the posterior for anything bigger than a pen gun.

Think about getting a floor pump:

If you want more power, bigger is always better.

Here's a simulation at 200 psi with a 12mm bearing, 24 inch barrel and 10 inch long 0.75 inch diameter firing chamber:

There you're doing 36 ft lbs. If I up the pressure to 300 psi, GGDT predicts 52 ft lbs. Moar pressue = moar power, no two ways about it.

[Ianbuckwell]

Just seen this and it has answered alot of my questions in other thread, I need to increase bore and pressure.

Does barrel length (thinking) either way of 24" by 8 under or 12" over have much influence on power output, I am guessing longer rthe barrel better the accuracy or is this not true?