Like stevelyn I too have had trouble lighting H-110 between about 0df and +25dF.
I personally sold my magnum and bought a Redhawk in .45Colt so I cold fool with a bunch of powders other than H-110.
I like all three of Universal Clays, HS-6 and TiteGroup from shirtsleeve weather down to -30dF.
The 270 SAA ought to be a terrific bullet against anything on two or four legs likely to be encountered in the lower 48, cast at about BHN 12-15 and driven to about 900fps with any of the three powders above.
I fooled a little bit with a 315gr cast Keith style SWC over the weekend. Hodgdon was expecting about 850 fps out of their test barrel with a smallish pinch of TiteGroup, so likely 650-700fps muzzle out of my 4" Redhawk. Pretty stout without over working the primers.
I am still looking for my bear load, but the nice thing about a capacious case like the .45Colt is it can get a lot of work done without having to lean on H110/Win296/H4227.