People have been shooting at this target for 75 years, and no one has ever gotten a perfect score. One competitor got a 50+24, but there is debate whether he had his scope cranked up beyond 4X. What's interesting is that despite the enormous advances in rifle accuracy we've seen in that time, the scores have not kept pace. A good score is 50+12. Usually, it's won with 50+17 or 50+18. Scores in the 50+20 range are infrequent. Thus it was 25 years ago when I started shooting at the sheep, and so it is today, despite the fact that the equipment is probably twice as good as it was in 1991.
I've predicted that no one will ever shoot a perfect score unless there's a radical change in the equipment that's allowed. If the rules are changed so that you can use a 10X scope, it's going to be a new ball game, or sheep game, as it were. Even so, the margins for error are so infinitesimal that it will never happen.