I have made 9 of them for customers over the years. I worked on 3 others that I didn't build. All were everything the customers wanted.
The 308 Norma is perhaps the best of the 300s overall. Some are faster, but none are better in terms of power and accuracy without excessively fast recoil and short barrel life.
It's not popular here in the USA, but I am sure I can't say why.

But like all the 300s, you should have a longer barrel then 21" I would not go less then 24 if I were you.