[IronJack]

Hanging fire.
Keep your powder dry.
The whole nine yards.
Lock, stock, and barrel.

[dmcnash]

Jumping the gun
Give him both barrels
Shooting blanks
Under the gun
Smoking gun
Gunning for
Hired gun
Stick to you guns
...and a thousand more

[Ditter]

“Lock and load”

[Fiji Hill]

Hanging fire.
Keep your powder dry.
The whole nine yards.
Lock, stock, and barrel.

"Flash in the pan" is also shootin' talk.