Tyranids always roll one D6 more than normal when checking to see how far they can move through difficult ground. However, if a brood of eight or model models rolls two or more 6's on the dice it suffers one wound from the stampeded (saving throws apply as normal).
Building an army? Create, validate and share your list with New Recruit, army builder for Warhammer 40,000 3rd Edition and many more games.
Try the builder