I have attached a photo of the tools I used to do the barrel work on my sporter. The thinner two piece of aluminum clamp (on the left) was used on the action. A small 1/8 pin is protruding from the face, it was up against the action to insure the clamp did not slip and it was plenty strong as my barrel was not super tight. This clamp was original split on one side only and the 3/8 Allen screw provided adequate tightening force. I had to split it into 2 pieces to get it inside the sight mount when the new barrel was installed and the extra screw was added then. The Crescent "auto" wrench used to provide torque. This wrench say on the side no extensions or hammering and it was fine with no "cheaters".
The larger clamp in the middle has 5/16 screws on the same side. It for the barrel and was held in the vice on the milling machine. With the 2 screws and the additional force from the vice it did not slip at all and I am fairly certain that anyone else could use the same set up and not damage a Krag barrel. This is assuming that mine was representative of all others.
I did bore this clamp out to tighten the nut that holds the sight base on my rifle, then split round bushing (right) was used to go back and hold the barrel. I am getting old and I do not remember why now.
If anyone is wondering about the custom trigger in the early photos. It was made 40 years ago when I was working in a screw machine shop and the only manual machines available were a drill press and surface grinder. I modified the cam surfaces so the gun fires immediately after the first stage slack is taken out. This was made for my other all original Krag after I broke the trigger in it. The trigger from this rifle was swapped to restore the all original Krag. If anyone else removes a trigger from your Krag, ask about which side to push the tapered pin out so you do not break the trigger like I did. There are a lot of knowledgeable people that hang out here and they like to help.

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