I doubt that a Saiga will shoot inside 1.5 inches at 100 yards. That's 1.5 MOA.
Your typical military rifle from a NON-combloc country will shoot 2-4 MOA at best, using commercial ammo. At typical commercial bolt rifle will shoot 1-2 MOA at best, unless fed unusually good ammo (handloads).
Thus, you are asking for commercial bolt action type accuracy out of a rifle that has the following inhibiting features:
1. Combloc barrel/action tolerances
2. Stamped sheet metal receiver
3. Short sight radius, with inferior "notch-type" rear sight.
4. Light but creepy trigger.
Given those characteristics, I would be happy if a Saiga gave 3-4 MOA.
By the way, it is well documented that a typical Combloc military AK-47/AKM will deliver about 6-8 MOA with milspec Combloc ammo, and about 4-6 MOA with commercial ammo.
I see no reason to expect a Saiga to be significantly better than this.