Who thought he 'd won

The field as certain as a gun.

Samuel Butler (1600-1680): Hudibras. Part i. Canto iii. Line 11.

For this is England's greatest son,

He that gain'd a hundred fights,

And never lost an English gun.

Alfred Tennyson (1809-1892): Ode on the Death of the Duke of Wellington. Stanza 6.

That's a perilous shot out of an elder-gun.

William Shakespeare (1564-1616): King Henry V. Act iv. Sc. 1.

As sure as a gun.

John Dryden (1631-1701): The Spanish Friar. Act iii. Sc. 2.