Twist rate is an optimal number based on the length of the given bullet and projected velocity. If the twist rate is too fast, the bullet will literarily blow up. Usually within a 100 yards. If the twist rate is too slow the bullet will begin to tumble though the air, although this is more uncommon and is generally only seen at extreme distance. You can see it on paper where the bullet doesn't cut the paper in a nice circle, it will create an oblong hole. Most bullet Manufactures publish the optimal twist rate for their bullets.
The published data isn't the gospel, for instance Berger recommends a 10 twist for their 210VLD, I know a lot of guys using an 11 Twist for that particular bullet.
A Remington 243 comes with a 9.125" Twist. That is a real general twist for a variety of bullets, it covers everything from the 107 grain bullets to the 70 grain bullets. But optimal for a 107 grain Target bullet (Longer than Hunting Bullets) would be an 8 twist. Which too is subjective. Some guys like 7.75" twist for longer bullets. Some guys will use a gain twist barrel, starting at the breech with 8.8" and getting faster towards the muzzle 7.5". Sierra actually recommends a 7twist for their 107SMK. Which by the way no one I shoot with uses a twist that fast.
Bullets tumbling or exploding will not be witnessed by the general hunting crowd. But under match conditions where guys are trying to push the accuracy envelope you occasionally see it happen. Most of the time when a guy is experimenting with different bullets vs twist rates. Say a 210VLD in a 14 twist, pushing high velocity, for sure you'll see a little black cloud of lead about 80 yards out. You probably wouldn't see it happen with the same situation under a reduced load. As you might see it tumble with the same bullet in an 8 twist barrel shooting 2000fps