I've got to say that while I am not a fan of combustions your guns are truly awesome
and all aluminum
ohh I've just noticed that post
do you mind if I ask what exactly do want to use as the chamber ? just a plain alu pipe or something else?
I suppose that building the chamber out of pipes and fittings (whether you buy them ready-made or machine them yourself) might not be the best option as far as price and mass is concerned
I think you could cut a lot of weight and make a nice compact gun if you use a HPA aluminium cylinder - for example something like this
of course if you can disclose that info... I am assuming it's not a secret?
set to be semi auto
lol you can add a large air cylinder to act as both the meter and to operate the bolt
ohh I just realized that's you'll also need a source of compressed air to pump the chamber... but I'll cut it now as I think I am asking too many questions that you might not want to answer