I have done a lot of work with Ti material, it is very difficult to machine vs stainless or Chrome-Moly. I make my recievers a bit larger than the std stock reciever for the added strength. I only do full bolt type receivers so there is not a lot of weight reduction due to the bolt being a larger dia it weighs more.
End product is an action that is very close in weight to that of a standard action only much stronger. (Like what James has stated) I usually go at least .100 larger dia on Ti action, rem 700 1.350" my Ti would be 1.450" dia.
I have built several for 408 C-T type wildcats, 1.700" dia Octagon style 11" long. It was right at 3# completed, the same in steel would of been over 5#, quite a savings in weight. This rifle with ABS carbon bbl, carbon stock was 11# finished weight.
It is very expensive to have a Ti billet deep drilled and Wire EDM machined, 300-400$ for a small run of parts. This would be the 700 Clone type of action. The full bolt action only requires the billet to be deep drilled and honed, much more reasonable. This is the reason you dont see more Ti recievers being sold to date. Tooling dont last very long, takes special taps and they are spendy.
I only work with Ti for specialty projects, it takes at least three times longer machining time. Mostly i build muzzle brakes
, firing pins and other small parts for weight reduction. I'm working on a proto type Ti action that will be the lightest and strongest avalible, i will post results when testing is started. It will have the 375 chey-tac chambered into an ABS bbl, total overall weight estimated 9.5# (bare rifle)
Depending on what cartridge your going to use i would just buy a Rem or Browning for the action.