I would never use a powder with SP10's characteristics in this roomy cased cartridge. A 68% fill-ratio is WAY too low. 90% plus is what you're looking to obtain with a normal pressure load, and even loads in the 80% range are 'lowish'. Doing a quick & dirty QuickLOAD run, I assume you're thinking of a charge weight around 40gn? If so, you're running at ~40,000 psi and this in combination with a low fill-ratio will likely give you very inconsistent velocities. As SP10 is a double-based ball type, it is possible it won't respond well to this mismatch - ball / spherical types often need quite high pressures, 50,000 psi and upwards, to perform as they're designed to and burn consistently.
Some years back a now defunct Portuguese outfit loaded FMJ ammo for various historic military rifles - 303, 8X57 Mauser, 6.5X55 and more. It also used the low fill-ratio / low pressure ball powder approach and although it worked in some cartridges, it was very poor in others (some say actually verging on dangerous), in particular 6.5X55mm Mauser where it produced sooted cases, large 'gas dents' in case shoulders, and it was alleged serious over-pressures on occasions.
Of the ball powders that are reasonably freely available, Ramshot Big Game is a near perfect match to 7X57 with a 130, 'Wild Boar' a little less so. The recently introduced Hodgdon CFE223 is an excellent match if you believe QuickLOAD (which you can't always, but it does usually point the right way at least), also the still slower burning long established H414, the only fly in the ointment a predicted 94.4% charge burn at 45,000 psi in a 24-inch barrel. (Will improve if you work charges up to the point where you break 50,000 psi.)
I personally would use Viht N150 here with this weight of bullet. For heavier projectiles, move to the slower N160. But there are many others - Alliant Re19, the 4350s, Lovex SO70, Reload Swiss RS62 which is also a very good internal ballistics match and gives higher MVs than N150 (which you may not particularly want of course). The Viht powder has the advantage of being one of the not quite as expensive as most and is very widely available in gunshops around the country, and is rarely out of stock waiting shipments from the factory.