Below are a couple of small excerpts from the chapter “Sighting In”, taken from the second edition of “Shooting the Bull”. Optical sights are strongly encouraged in order to get the most usefulness out of any projector. The trajectory charts mentioned are placed on the index cards in a table style of format for easy reference once you are in a pasture setting. (Make backup copies to store at home as you would not want to have to do all the work over again in the event you lost your “field” cards.)
In the book, impact trauma is mentioned several times. RDDs should strike animals with just a slight amount more force than is required to implant the RDD’s needle into the tissue. With excessive impact you are not only unnecessarily bruising the animal, you are also inviting your RDD to bounce out and waste your drugs. Should this happen you have two choices for your next shot. Either turn the power down on the projector, or get further away from the animal. If you do not observe “arc” in the RDD’s flight towards the target, you are most likely shooting it too hard.
“Your goal should be to float the RDD into the animal. Keep in mind that you are shooting a projector and not a 30-06. Also, an optical sight is not for magnification, but is utilized as a precise aiming point. There can be instances when the sight needs to be held 12 inches over the crown of a calf’s neck at longer distances in order for the RDD to strike 6 inches below the top of the calf’s neck. Iron sights just cover up too much real estate at longer distances, making precise holdover estimation very difficult.”
“Document your work and make a trajectory chart as you proceed. I always list the RDD capacity at the top of an index card, and have a separate card for each size RDD. An example of one of my charts is pictured at the end of this chapter. I use five yard increments of distance. Let’s say you used a 7cc RDD and now have it zeroed at 20 yards. Again, you have picked this capacity as the one that you will most often use, and the 20 yards is the most common distance that you will be doctoring your cattle at. Move your target to 15 yards, turn the power on the projector down, and shoot another group. If it does not zero out, but is striking plenty hard, measure the group you have and reference where you need to “hold” your aiming point in relationship as to where the practice RDDs are hitting. In other words, if at 15 yards your group is striking 4 inches lower than where you are aiming, write down under “hold” (+) 4”. When you get out in the field and want to make a perfect injection, you will be holding the sight four inches higher than where your RDD is going to hit at this distance. The same is applied for negative hold. If groups are hitting above your point of aim, but are not striking excessively hard, your hold should be that distance held below the injection site. You should reference this in the hold column of the trajectory card as (-4) inches.”