chamber size

[Spudblaster]

would a 4"x30" chamber be too big for a bicycle pump? combustion would be too loud for where I want to use these. I intend to attach a 5' tennis ball barrel and I think anything less then 30" would not be optimum. any insight would be helpful

[Lockednloaded]

well its really a matter of how well you want this gun to perform/ how much work you want to put in. I've pumped a 3"x16" chamber to 120psi... not that fun.\, but i always like to think that the energy put in will equal the energy of the shotnot true, but it makes my aching arms feel better. Your valve will also determine how big you want your chamber to be. A little more detail would be helpful and you could also play around in GGDT

P.S.
We have quite the infamous Spudblaster here already

[Ragnarok]

A two and a half litre chamber with a bike pump? Depends on the bike pump. A vertical track pump would be alright, but a hand pump would a problem.

I'd note however that a chamber of that size would be very noisy - a pneumatic can be just as loud, if not louder than a combustion.
In truth, if you're looking for a quiet launcher, I'd actually say a combustion has a lot of merits. Provided you get the right chamber to barrel ratio, then they can be a lot quieter than a pneumatic.

P.S. We have quite the infamous Spudblaster here already

Yeah, you've got to laugh when a new member comes along with a username only fractionally removed from a forum regular.

Myself, I never use usernames that have any relation to the subject of the site - they're too likely to be similar to other people's (be they current or future members).

[Lockednloaded]

you could also cut down the chamber by a whole lot and up the pressure, granted you have a setup that could produce high pressure. This gun is a perfect example of high pressure compensating for chamber volume