It is not a great trick to push a 200-220 grain cast GC bullet out of a Krag at 2K velocity. There are any number of powders and bullet combinations that will do that. Now comes the "but"...but, doing so with good accuracy is a great trick. It can be done, but it takes work.
The problem comes from the rifle itself. The barrel groove diameter can vary greatly. They run from .308 to as much as .315 in the grooves. .310 groove diamter is common. So, now you have to find a mould that fits the throat and groove of your barrel and many will not. There is also the problem of the nose riding portion of the bullet being the correct size.
Let's add the fact that these rifles have very long throats and when most cast bullets are seated out to touch the rifling, the rounds are too long to feed through the magazine. Seat the bullet deep enough to feed and accuracy suffers.
As far as powders go, I am having great luck with WC872 for full 2K loads and 4759 for 1.5K loads.
I have not tried every mould yet, but thus far I have had the best luck with a 220 grain Hensley and Gibbs design and good old Lyman 311291. 311291 only weighs 170 grains or so, but does fit the Krag well. I have several of these moulds and one DC cast bullets that run .316 on the body and .302 on the nose (No. 2 alloy). One of my Krags runs .3095 in the grooves and the other a full .311. I size my bullets in a .311 Lyman die, which in reality sizes .3117. Any bigger than this and I have problems chambering the round without neck turning the cases to give a little clearance.
311291 can be seated with the first lube groove just covered by the neck of the case and this bullet will fill the throat and the body touch the riflings while the nose engraves .001 - 002 on the top of the lands. This bullet so loaded will also feed like glass through the Krag magazine.
For 2K loads I load a 50 grains of WC872 with either bullet. I get 2-2.5 MOA groups with either bullet.
However, 311291 loaded over 16/459 with 2ccs (20 grains) of shotshell buffer on top to form a slightly compressed load will give a full 1.5 MOA with a velocity of 1,600 fps. I am talking ten shot groups all day long. This is all these old girls have to give in terms of accuracy.
So..I have been trying to put together a 220 load to match the old military load, it is easy to match the specs, but gilt edge accuracy has thus far eluded me. I continue to work with new bullets and maybe I will find the magic combination...In the mean time I shoot lots of 311291/16/4759 with outstanding accuracy and no stress on the hundred year old rifles.
Sorry for the long post, but I got carried away..I do so love the 30-40 round the rifles chambered for it.