Quote Originally Posted by Henry Rifle
The old wives' tale about Grade 8 breaking easier than Grade 5 is just that - a tale, a falsehood, a myth. Kitz - who has much more knowledge in that area than I do commented on it sometime back. Grade 8 is stronger in both tension and shear than grade 5.

Read THIS for more info.
Yep, exactly correct.....That's the same article I linked to