There may be a safe load but it won't be very fast as compared to some other powders. In my IMR guide for the Federal plastic field shell it states: 20.5 grs. of 700X with a Brenneke slug for 1230 FPS. 37 grs. SR 4756 for 1525 FPS
Both using a Fed 209 primer. A slower powder will give more speed. I'd use the 700X for target shells and get a 8 OZ can for the slugs when you can find a load. Check with Ballistic Products, they print a loading pamphlet on slugs that I believe has data for that slug.