Das ist schwierig. Da sonst niemand die Anfrage beantwortet hat, versuche ich es mal.
to step in the way of an assassin's bullet
Hast du einen ganzen Satz?

catch the bullet

is fine

Meet the agents inside the Secret Service
They'd Take a Bullet For The President

Headline for an article in "Parade" magazine.
http://www.parade.com/news/2009/01/they-would...

"Take a bullet for someone"

is also a standard phrase.

("Bite the bullet" is, however, something entirely different. :-))

"but still, I'd leap in front of
a flying bullet for you..."

for a more lyrical approach...

Danke!