From Pathfinder Guns & Gears, which isn't enabled.

Silencing Shot

ITEM 11

Price 300 gp

Bulk —

Ammunition any

Activate (concentrate)

This shimmering, golden-hued ammunition never makes any sound. A creature hit by a silencing shot is subject to the effects of a 4th-rank Silence spell unless it succeeds at a DC 25 Will save.

Craft Requirements Supply one casting of silence at 4th rank.

Pathfinder Guns & GearsORC