You also need to use a different drag law for slugs, (G1) I believe. ChairGun will get you close but BC changes with velocity so it will be off at longer distances. Strelok is better for slugs IMO because you can enter multiple BC’s for different velocity ranges.
Strelok Pro has all the NSA slugs in their database. For most slugs I use the RA4 profile vice the G1 profile. Seems to work better and be more accurate for distances greater than 150 yards. Shorter than that it doesn't really matter.