Gismo, American Krags have a guide rib alongside the bolt that ends just short of the right side upward extension of the receiver. It a shows clearly on Steve Hughe's photos, above. On Norwegian and Danish Krags this rib extends further to the rear and fits against the receiver shoulder, forming a second locking surface, albeit it is not symetrical with the front lug. It is possible to alter a US Krag to lock up like this too. There are three methods. First, you can relieve the rear face of the bolt locking lug which lets the bolt go a bit to the rear. But this increases headspace so this method only works if you are rebarreling. It also can cut through the hardened surace on the back of the lug. Alternatively, you can weld up the front of the receiver shoulder. Disadvantage, risk of spoiling the receiver. Third method and the one I use, weld up the rear face of the guide rig. Disadvantage, spoiling the bolt, but Krag bolts, even brand new ones, are in good supply and out of perhaps half a dozen I have yet to ruin one. Another disadvanage is that if you shoot in the rain, your zero may change. I understand that for that reason Norwegian military rifle matches were shot on ranges with roofed firing lines.
