GR translation: hammerfall and doomcrack

[David Morris]

"Hammerfall" refers (I think) to a gun's hammer as it strikes the bullet.
"Doomcrack" would be the sound of the explosion.

On Tue, Dec 13, 2011 at 1:40 AM, Mike Jing
<gravitys.rainbow.cn at gmail.com> wrote:
> P26.1-7   It’s nothing he can see or lay hands on—sudden gases, a
> violence upon the air and no trace afterward . . . a Word, spoken with
> no warning into your ear, and then silence forever. Beyond its
> invisibility, beyond hammerfall and doomcrack, here is its real
> horror, mocking, promising him death with German and precise
> confidence, laughing down all of Tantivy’s quiet decencies . . . no,
> no bullet with fins, Ace . . . not the Word, the one Word that rips
> apart the day. . . .
>
> What is "hammerfall and doomcrack" referring to here?