This is an easy one to give a rough answer Rocky.... Just for fun.
(Although I can say that in my professional life, I have rarely ever seen a hit probability distribution that was actually a "normal distribution".)
Since we called it a 1 MOA rifle, that means it would be for 6 SD worth of the group. So, from that starting point, the probability for the first part of your question is roughly 100 percent because you are covering that with your definition. For this to be called a 1 MOA rifle, all 10 of those shots are within the 1 MOA.
If we keep looking for the probability of the inside 0.5 MOA, then roughly speaking there would be roughly 80% of them. Your probability is roughly 7/10 - 8/10 should land inside the 0.5 MOA zone with an 1 MOA rifle. So any given single shot has about 7 to 8 out of 10 chance of landing inside 0.5 MOA, but only in a perfect world....
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