FWIW: To fit the barrel-band, I suggest you take your rifle apart.

Make sure the top inside radius of your barrel-band matches the radius of the barrel at the point where it will be located.

With the barreled/action off of your stock, check the fit of the barrel-band to the wood.

There is an obvious shoulder that positions on the top of the barrel-channel.

The inside radius of the lower part of the barrel-band is a 'pattern' for the front part of the forearm wood contour.

Once the forearm tip can easily enter the barrel-band, you can reassemble your Krag and use the barrel as a guide as you slowly remove & contour wood and carefully fit the band into position.