The XR-003 Sapper Explosive Delivery System exclusively appears in Resistance: Fall of Man and is obtained from a dead SRPA Black Ops soldier. The weapon fires organic explosive globules based on those used by the Widowmaker. This explosive material is highly sensitive and likely to explode when approached. Due to this, they are able to serve as proximity mines, or can be remotely detonated from the Sapper's secondary function.
Try to preempt where the enemy, especially quick ones such as Leapers and Gray Jacks, is going to move, and lay down traps for them. As soon as the sacs sense an enemy nearby, they will explode causing considerable damage if a cluster has been left.
The XR-003 "Sapper" mine launcher is believed by British Intelligence tp be the product of secret US weapons programs. Pressing R1 fires a stream of organic cluster mines. Each mine is encased in a living cell similar to those used by the Widowmaker. The mines stick to most surfaces, including each other. In combat, the Sapper can be used most effectively by setting large cluster mine traps for ambushing Chimera. Aiming at a mine and pressing L1 will detonate the targeted mine. Other mines within the blast radius will also explode. Holding L1 detonates all mines in the vicinity.
The Sapper is believed British Intelligence to be a product of a secret U.S. weapons programs, which can be proven correct upon the release of Resistance 2 and the introduction of SRPA. It can be presumed that the U.S. Armed Forces replaced the Sapper with the HE .44 Magnum.
In the Resistance 3 extras video "Remembering R1," it is shown that the Sapper model was originally assigned to a totally different weapon, a physics manipulator resembling the Gravity Gun from Half-Life 2. Developers state that the weapon was axed in this form because it could not be made to function correctly in time to make the ship date.