Yes, it is common for the firing pins on AK and AK Variant rifles to leave a dimple mark on the primers. This is due to the firing pin being free floating, without a spring containing the firing pin. So when shaking the bolt, you should hear the pin move freely. However, when the round is chambered, the inertia from the free floating firing pin within the bolt, will travel slightly forward just enough to dimple the primer. This is also common on AR15's/M4 rifles. So, go ahead and purchase that Saiga.
Have gun, will travel :50cal:
By the way, I am still clinging to my guns and religion