I am in the process of building a parts Krag, using a model 1898 receiver picked up at a gun show, and an altered model 1896 carbine barrel, purchased on ebay.

The threaded breech of the 1896 barrel was too sharp-cornered to screw fully into the receiver. A slight bevel was put on the threaded barrel-shank to allow full seating into the receiver.

A bright 'ring' on the inside corner of the receiver barrel thread (from contact) allowed me to estimate the slight bevel.

This model 1896 barrel has an unofficial 'dovetail' added to the bottom of the barrel. (A gunsmith had made this modification for a drilled & tapped forearm anchor).
This bottom dovetail allowed me to use a piece of brass stock, opposite some laminated hardwood, to securely grip the barrel in a regular bench-vise. (Some blemishes and old vise marks were already on the barrel, when it arrived).
A 'nut' style Krag-action fixture, made by KCA member - 'Rcat7147', allowed a 'Monkey Wrench' to be used to fully screw the Receiver onto the barrel. (I put some 'Locktite' sealant on the barrel threads prior to final install).

The barrel over-rotated slightly so the Index Marks are a couple of degrees out of alignment. I had to slightly widen the notch on the barrel breech for the nose of the extractor. The rear-sight is slightly 'canted' to the Left.
I tested three Krag Bolts. They will close on a loaded round, but, will not close on my Field Gauge.

When I finish installing a 'banded' front-sight, "it will be off to the Range" to see how the barrel performs.

---