Primers Every Time

If primers don't feed every time, check the following; The case sensor spring may be installed correctly, but something may still be preventing it from fitting all the way into the slot cut for it in the primer pin pocket. The straight leg of the sensor spring must protrude far enough into the primer pin pocket to fit under the shoulder on the primer pin. This is what holds the primer pin up high enough to prevent a primer from sliding down the trough. Check for powder in the primer pin pocket, or in the slot cut for the sensor spring.

Another possibility is something under the primer trough, preventing it from being pressed all the way down into the shell plate carrier casting. Again, look for powder or other foreign objects.

Last, look for an over tightened case sensor retaining screw, or a sensor bushing installed upside-down. Either will prevent the case sensor from pivoting correctly, and could cause the case sensor to hold the sensor spring in the "out" position.