I made this one a couple of years ago:
The barrel in it is for my savage 112BVSS 7mag. I originally planned to bolt it to the bench but clamping it to the mill table works great.
I machine aluminum inserts from chunks of 1-1/2" Al rod to fit the barrel of the rifle I'm working on and save them. Over time I'll have a set of the ones I need.
I've used it to work on Savages, Remingtons, Mausers, Winchesters, and Springfields. Works just fine. The clamp bolts are 1/2-20 Grade 8 bolts. I torque them lubed to 90 ft-lbs. No problem with slippage so far.