The faulty round, that failed on steenbok, I put in pocket to keep separated from other ammuntion. On arrival to my room I examined it more closely.
There was only a hardly visible firing pin scratch on the primer.
The round did not go off, because primer was too deeply seated in the casing.
I took it back home, and will try to test it on next range session.
For those who were following my report earlier:
Today I went to the range, and test fired the norma swift a frame, 300 grains, that did not go off when badly needed on steenbok.
After examination, upon failed to fire, there was no trace of firing pin striking the primer.
Not a scracth.
My conclusion at that point was that primer was pressed to deep, and firing pin did not strike the primer.
And then, I decided to test again, on first chance.
Today, at range:
On test firing it surprised me, and in the same time did not.
So, the round was chambered, trigger squeezed and round went off, in a usual manner to same poi as zeroed. (business as usual?)
1. I was surprised because this time it went off, but the question remained why it did not go off, during the hunt when really needed? This, will remain without answer, for time being.
2. I was not surprised, because in my experience, sometimes it happened that old mil surp ammo, vintage 1953 (and similar), sometimes does not go off. Then, on second attempt, it usually does. (8x57, in vinatge k98).
But on the other hand this should not happen with brand new, premium ammo, out of factory, such as norma. (?!)
So, i came to current conclusion, nothing is 100% safe or certain.
Photo of fired subject casing below. (with very good indent on primer)