You might try the fellows over on Double Guns, this site is dedicated to Single Shot Rifles and primarily cast lead bullets. There is wealth of knowledge to fit your immediate need and a great bunch of fellows to go with it over on the Double Gun site.

I've shot some with jacketed in my 30/40 HW, match rifle.

With 168 Sierra match bullets, 31.0 gr of AA2520, shoots about as well as 45.0 gr H414 (top end for the Krag bolt). 31 gr 2520 will also give excellet groups with GC cast bullets.

45 gr of H414 gave me my best ever group (.312 @ 100) with that rifle, using the old Speer 190 match BT but, it's over pressure for the Krag rifle. You might try about 41.0/42.0 gr with a 180 gr.

Frank

The Krag has almost the same case capacity as the 308Win.
You might look at heavy 308W cast bullet loads in the 
handbooks and here, but use your jacketed bullets. Just keep at or below these 40,000 cup type loadings.

As for a bullet, if for deer, consider the 170 gr 
"30-30" type RN jacketed bullets. The Rem Core Lokt
170 RN does in deer quite well shot out of a 308 
at modest velocities-2300fps or so,  in the "Krag" range.
beltfed/arnie