Magnesium or very lightweight rifle chassis

Those two are really the lightest I've found ; You can find the XLR carbon used for quite a bit less, it isn't quite as light but its still pretty light.
 
The hunt26 dampens vibration better than a xlr magnesium. If folder isnt an absolute must, I'd get the new manners LRH with carbon arca rail and carbon mini chassis.
 
Might be a bit pricier, but the Q SideChick chassis is extremely lightweight (about 2.5 lbs) for what it offers. I've got a .223 barrelled action in mine, and it's excellent. Incredibly adjustable, without feeling like a boat anchor or a canoe paddle in form factor.