Kevin, the graduations in range are only correct with the exact sight radius the original rifle had. If you are interested in using the range marks on your new Krag sight I will bore you with some simple math which will enable you to use the Krag sight effectively.
First you need to know the trajectory of your new rifle and ammo. There are free trajectory calculators online, here is one
http://www.biggameinfo.com/BalCalc.aspxIn my BC I shoot a 405 grain bullet at 1300fps, ballistic coefficient is .259 for my bullet. I zero at 100 yards. Drops are in Minutes Of Angle (MOA), not inches. One MOA equals approx. 1 inch for each 100 yards so 4 MOA at 400 yards is 16" and 1 MOA at 50 yards equals 1/2".
My drop chart in MOA:
50 - +4.16
100 - 0.0
200 - -12.09
300 - -26.64
400 - -43.11
500 - -61.36
600 - -81.36
For mid ranges like 350, 450, 550, you can take half the incremental drop and be very close (it is actually about 45% of the incremental).
Now, the graduations on the Krag sight can be used but the numbers on the sight will only be references. They will have nothing to do with the actual range in hundreds of yards. Start by determining the exact length on your sights that equals 1 MOA. This is easily accomplished by multiplying the sight radius of your new rifle by a constant (.000291). Just trust the constant. It is correct. If I tried to type the explanation my fingers would fall off. If you really need to see it then get a copy of E. C. Crossman's "The Book of the Springfield". The sight radius on my BC with Krag sight is 31". 31 x .000291 = .009. So the length of 1 MOA on my sights is .009". You will need a set of calipers to measure this on the sight or you can get a 1903 sight micrometer from here
http://www.ray-vin.com/ which might work on your sight, it does on mine but mine is a little different from yours.
So, you just zero the rifle at 100 yards then add or subtract the MOA from the drop table using your caliper. Once you know the setting for any range you can write down the number from the Krag sight and use it is a reference. For example, zerod at 100 my Krag sight shows "3". So in order to hit the steel targets at 400 yards at my range I use my caliper to add 43.11 MOA or 43.11 x .009 = .38799 or simply .390". To get to 500 yards I would add an additional 18.25 MOA or .164".
Easy right???