Mickey,

An intercepting sear is a second sear that is not normally engaged in its notch or bent on the hammer. This to keep the trigger pull light and clean as can be had with just the primary single sear. A DR equiped with them will have two intercepting sears. The intercepting sear for, say the right barrel, is disabled, by rotating out of the way, when the trigger for that barrel is pulled, allowing the hammer to drop home when the primary sear is moved out of its notch or bent by the movement of the trigger.

If the trigger is not pulled but the primary sear lets go, the intercepting sear which has a larger, deeper notch or bent, will catch the hammer, ie, intercept the hammer, before it can strike the pin.

The intercepting sear only works when the rifle has malfunctioned since the primary sear shouldn't let go without the trigget being pulled. On the other hand it allows a rifle equiped with them to have nice, light trigger pulls without risk of accidental discharge from mishandling or from doubling due to recoil.

Shotguns equiped with intercepting sears work the same way.

JPK