Paul, Thanks for your perspective on AA2520 powder and your responses to my other posts over the last few weeks as I try to "get up and running" with my Model 1899 carbine.  Evidently, AA2520 has not been used by forum members.  I wrote to its maker, Western Powders, and they shared that they have not tested 2520 with the .30-40 Krag cartridge.  However, they ran a couple of projections and sent me .30-40 load data for 165 gr and 180 gr loads.  In a few months, I may try their starting loads with those 2 bullet weights.
In the meantime I continue to work on hitting paper with the rifle.  You may recall that I was 24" to 28" high at 50 yds using IMR 4198.  I recently bought R/L 15 along with Hornady 220 gr Interlock bullets.  I have loaded 20 rounds with 30 grs of R/L 15; and 20 rounds of 180 gr Hornady RN atop 40 grs of IMR 4350.  I had planned on testing these 2 recipes at the range today, but the wind has been gusting at about 50 MPH all day. I will try to get this done later this week.  Lastly, I bought 2 boxes of Hornady 180 gr factory ammo.  It is possible that I am doing something horrendously wrong in my reloading process.  That will be confirmed if the Hrn. factory ammo shoots accurately.