I have one and have seen another 1898 rifle, (both have great bores) that have 3 holes drilled in the receiver . One at the top and the others down about 60 degrees. each are about .250" . My hope is to pull the barrel, have the holes TIGed up and re-heat treat the receiver. With that , I will move forward to get it shooting again. Any information you can share will be appreciated. Thanks, Mark

I am with Cat Man on this. I recently learned from a fellow member that the case hardening was done in a cyanide bath. I thought they used the old bone and leather type of casing. The base metal in the receiver is a very low allow steel with a not very deep case and a very soft core. Around the filled holes you will get a blended alloy that would harden and temper very differently from the base material.
I would be flinching badly with such a gun wondering if the next time I pull the trigger something bad was going to happen.

'MkII' - I'm just curious. Do the three holes enter the barrel/chamber and compromise the barrel?

Photos of what was done to this Krag would be interesting to KCA Forum members.

I remember someone, maybe Butler's Rangers saying which case method was used on Krag parts. I maybe all wet but I think it was said that cyanide was used.
No possible ill effects for the end user since the parts were quenched in water and the krags have been cleaned a million times since they were made. For those doing the actual work precautions would have been necessary.
Here is a quote from Wikipedia
"Cyaniding[edit]

Cyaniding is a case-hardening process that is fast and efficient; it is mainly used on low-carbon steels. The part is heated to 871-954 °C (1600-1750 °F) in a bath of sodium cyanide and then is quenched and rinsed, in water or oil, to remove any residual cyanide.
2NaCN + O2 → 2NaCNO2NaCNO + O2 → Na2CO3 +CO + N22CO → CO2 + C
This process produces a thin, hard shell (between 0.25 - 0.75 mm, 0.01 and 0.03 inches) that is harder than the one produced by carburizing, and can be completed in 20 to 30 minutes compared to several hours so the parts have less opportunity to become distorted. It is typically used on small parts such as bolts, nuts, screws and small gears. The major drawback of cyaniding is that cyanide salts are poisonous."

Please note the case is very thin, so on a Krag with low alloy steel under the case little strength is there. You do too much polishing when bluing and you really hurt the strength and wear resistance of the steel.
As to who did it and how. I would like to see documentation and drawings or photos of the whole process of building a Krag. The setups and machining processes involved in making the Krag are hard to envision. The heat treating and stock making would have been a wonderful processes to observe also.  I think some of the later guns have some documentation on the processes in manufacturing, but I have seen nothing on Krags.

Whoops!
BR<
Cyanide was mentioned by someone recently, since you share so much good info I was thinking it was you.
You have done it again with that last post. Are the publications you just mentioned readily available.
I am a little afraid to look at them, I maybe tempted to build a new action and bolt out of L6 tool steel and chamber it for an elephant cartridge.

Found the Springfield Armory articles - (note they share pages with other articles).

The Scientific American articles on Springfield Armory appeared in Vol. LXXX, No.17, pages 267 & 268, (April 29, 1899) and Vol. LXXX, No.20, pages 330 & 331, (May 20, 1899).

Where did the heat treating chemicals go after use?  Where did the wash water go?  Was/is there a Springfield version of Love Canal.  Lots of this sort of manufacturing in Springfield and in the other cities of CT & MA, not just the Armory.

Reinc,
Not sure which biologic process would be involved in breaking down the cyanide remains but it is made of sodium, nitrogen, carbon, and oxygen. I doubt there would be anything toxic left after break down. It is only poisonous in the blood because it prevents oxygen from being transported. After the carbon in the original process was pulled into the steel most of the remains in the boxes would not have been "cyanide" anyway.

BR,  I am glad there is not enough info in the articles to duplicate a Krag, otherwise I would have to start telling myself I am too old to start a project like that. Anyway thanks as it is interesting info.