The Krag Jørgenson: Working up a Load

 

My 1896 Krag Jørgenson and Mills Belt

I was recently fortunate enough to acquire an 1896 Krag Jørgenson rifle in nearly pristine condition.  I loaded 20 rounds of ammunition, with five rounds each of 4 different powder loads to determine which shot best in my specific rifle.  10 rounds of each would be more precise, and I will test later with that many when I tune these results, but my goal was to get a rough idea of where to start.

As always, my goal is to attempt to match original ammunition as closely as possible, but that is difficult in this case since they used smokeless powder and modern powders are different.  I was told that IMR 4350 is very close to the Dupont powder used in period, so I used that along with a Hornady RN interlock bullet weighing 220 grains since it is a very close match to the originals.

Original Krag .30-40 cartridge design.

My reproduction cartridges.

I will post a detailed discussion of my loading procedure later, but the key here is to note that I made four different loads:
Load I:    34.5 grains
Load II:    36.5 grains
Load III:   38.5 grains
Load IV:  40.5 grains.

Load IV came closest to matching the velocity of the original cartridges at just over 2,050 f.p.s., with the originals coming in at 2,000.

I shot each Table of Fire at 100 yards from a rest, with a 6:00 hold using a full sight picture (this will be important below) on the black disk shown on the target pictures below, with the disks being 3 inches in diameter.  The day was bright and sunny, temperature 85 deg., wind from 3:00 at 10-15 m.p.h. with 27% humidity.

I will show the target pictures below along with the string test results.  I will show the Figure of Merit for tables 3 and 4 only since the FoM is tedious to go through, and these (representing Load III and Load IV respectively) were the best of the day.

To learn more about the Figure of Merit and how to do it, along with a link to a calculator to do all the hard work for you and to a video I made showing the theory behind it, go here:
https://historicalshooting.blogspot.com/2021/01/calculating-figure-of-merit.html

To understand the String Test, go here:
https://historicalshooting.blogspot.com/2020/12/the-string-test-measure-for-historical.html

Table of Fire One: Load I
String Test: 27.5 in./5 rounds = 5.5 in./rd.

Table of Fire 1: Load I.

Table of Fire Two: Load II
String Test: 9.5 in./5 rounds = 1.9 in./rd.

Table of Fire 2: Load II.

Table of Fire Three: Load III
String Test: 8.25 in./5 rounds = 1.65 in./rd.

Table of Fire 3: Load III.  Note that all the spots are from a neighbor trying out birdshot at 100 yards!

Table of Fire Four: Load IV
String Test: 9.25 in./5 rounds = 1.85 in./rd.

Table of Fire 4: Load IV.

So, from these results, it would seem that Load III gave the best results with a String Test of 1.65 in./rd., which is, incidentally, far, far better than I have ever achieved with any other rifle at 100 yards.

Next, however, we will consider the Figures of Merit for Tables 3 and 4, which will show that the mean radial deviation of Load IV was slightly better than that of Load III.  Remember that the FoM only determines the consistency of the group, not how close it came to actually hitting the spot at which you are aiming, whereas the String Test takes both factors into account, just not as precisely.

Here is the target diagram and FoM calculations produced by Rob Enfield's FoM calculator (see the link above) for Load III:

Load III FoM target diagram.

Load III FoM calculations.

Here is the target diagram and FoM calculations produced by Rob Enfield's FoM calculator (see the link above) for Load IV:

Load IV: FoM target diagram.

Load IV FoM calculations.

Thus, from these results we can see that both loads III and IV are excellent, with very similar String Tests and Figures of Merit.  In this case, however, the String Test results actually tell us something important that gives the lie to the seeming superiority of Load III when trying to reproduce the original cartridge:  The Krag sight was designed with a 200-yard battlesight, meaning that at 200  yards you should hit precisely on your point of aim when using a full sight picture.  Since I was shooting at 100 yards, an accurate reproduction bullet should hit slightly high, as these with Load IV did when using a full sight.  This fact, combined with the fact that Load IV came closer to the 2,000 f.p.s. muzzle velocity of the originals, shows that Load IV is a superb reproduction of the original cartridge.