How long will the muzzle flash hider be?

I assume from 50 mm to 100 mm(?).

If so, a 15 inch or 38 cm barrel would be better anyway. IMO.

I don't know how long a barrel would have to be to burn up the powder properly and what the shortist practical barrel in 7.62 can be had in military rifles? But doubt normal ammo would burn all the powder up in such a short barrel.

For a follow up shortish barrel rifle for wounded boar, I would go for a heavier calibre size.