A Necessary Evil?
As we pour over the literature and listen to advice to develop our shooting and hunting skills, how often do we hear that a fouling shot is needed before going into the field to hunt? This advice tells us that a fouling shot is needed to ensure that our first hunting shot and follow up shots have more or less the same impact points. The advice is made extremely credible because the folks providing it are among the most accurate shots around.
It is all too easy for the developing hunter to experience a bit of frustration when listening to expert advice tailored for shooters with skill levels well beyond his or her current abilities. While a fouling shot frequently makes a difference for the top competitors, it is not usually important for the average deer hunter.
We explain why this can be true and offer suggestions on how to verify this conclusion for your rifle. The suggested effort has the added benefit of quality trigger time which will help one be more comfortable with the rifle and how it shoots.
The Attention Getting moment:
A humiliating moment at the range caused one of the authors to take a closer look at changes of impact caused by fouling and barrel heating for follow up shots taken during a hunting trip:
I went to the range with a family member. He shall remain anonymous. I told him truthfully that I had zeroed the rifle on my last shooting session so that five shots in the x ring could be covered by my thumb nail. Hence all future shots including that day’s would be in the x ring. I said I would shoot first to show him the rifle’s accuracy and we would remember that the first shot in the x ring was mine. Other shots in the x ring would be his. I fired the shot. To my horror it was inches off dead center. It was still in the black so technically would have resulted in a fatal wound to the target but inches off from the center of the x ring of the target. That was not supposed to be. I was embarrassed. I wondered, “What could I have done wrong?” I said very little more that shooting session.
That experience led him to search for the “true zero” for his scope through an experiment comprised of a series tests over a large part of a year. The experiment consisted of tracking the impact points for each of the first five shots during a range session. The experiment was repeated with reloads using different weight bullets over the same powder charge to determine the effect of changing bullet weight at 100 yards.
Those tests showed that his shots generally placed within 2 or 3 moa. Wow, what terrible accuracy you say!! A serious bench rest or long range varmint shooter would certainly draw this conclusion. We maintain, however, that this is acceptable hunting accuracy if it truly represents what you and your rifle actually do while in the field.
Here’s Why:
Figure 1: Example Target from Fouling Shot Testing. We see that the second and following shots are closer than 1.4 inches away from the first shot. Also, the 1.42 inch group size is well within the 3 inch diameter needed to be sure of hitting vital zone at 300 yards. This suggests that a wisely chosen zero will make this a 300 yard rifle.
The canonical 10-inch diameter vital zone is about 3 minutes of angle across at 300 yards. While the fouling shot advice is excellent when sub-moa groups and long range precision shots are contemplated, almost all hunting shots are taken from within 300 yards. Yes the outdoor adventure shows glorify shots at 400 yards, 500 yards and even further out, they do not represent you and the majority of us hunters.
Having acknowledged that 2 to 3 moa gives one an excellent chance of reliably harvesting medium game out to about 300 yards, we still advocate striving for the best possible accuracy. The more accurate your shooting at the bench and small targets, the more confidence you will have in getting the bullet into the middle of the vital zone.
Further, we conclude that, for many rifles, the difference in impact point when using a cold-clean bore and a cold-dirty bore is well within the 2- to 3-MOA max spread for reliable hunting shots out to 300 yards. The 3-MOA assumes a 10-inch diameter vital zone and that that you make the necessary range and wind corrections when more than 150 to 200 yards. Indeed, the differences in impact point will remain within the 3-MOA circle over a significant range of bullet weights for normal hunting ranges.
Does this mean that one can get by with a single range session and be OK if the first three shots at 100 yards impact within 3 inches of the desired point? Absolutely not. You need to do several range sessions to be sure the rifle, sighting system and ammunition give consistent results from day to day. One also needs to determine where the “First Shot” tends to hit so the sights can be adjusted for the most important shot. Finding where “Follow Up Shots” impact verify that they hit within the desired area with the newly established sight settings.
You ask “Why not sight in using the group obtained when shooting three to five shots in a two to ten minute period? The first shot truly is the most critical because it is frequently the only one you get. That means that the sight in needs to reflect the area where the first shot is likely to hit. The follow-up shots only need to be in the vital zone.
Our tests show that the second and third shots tend to cluster in a slightly different area than the first one. Therefore, our range sessions need to verify that these shots tend to be within 1.5 moa of the first to ensure the entire group is within the canonical 10 inch vital zone at 300 yards or within a 3 moa circle at that range.
This suggests that one needs to complete several range sessions, each of which starts with a clean bore or a dirty one if you are comfortable storing the rifle in that condition. The first shot is taken on one target while the second and third are taken on an adjacent target. Retrieve these targets to use again during the next trip to the range. The first three shots are followed with whatever range and practice activities you like to do BUT ON DIFFERENT TARGETS! You need to preserve the first pair of targets to learn how your rife performs over a span of time.
A related and occasionally critical issue is the question of how far off of your standard zero does different ammunition strike?
Back Up Ammunition
Recent USA buying panics suggest that there will be occasions where your favorite ammunition or components are not available at the store or online. Actually, there are multiple reasons why you may not have your favorite hunting ammunition on the day of the hunt. The obvious question deals with how to prepare for this so a hunt won’t be ruined for lack of ammunition.
This question is expanded with observations by one the authors during his experimental campaign:
The research question I am facing today is to find the one “true zero” if it exists for the scope of my rifle. Typically, I measure the data every shooting session and make the incremental adjustments when it seems they are needed.
The problem was further defined when I was having trouble getting ammunition for a while, a couple of years actually, and was dependent upon the kindness of strangers to get anything to shoot without regard to manufacturer or bullet weight.
It seemed I was making too many little adjustments. Every time I changed manufacturer or bullet load I had to move the zero on the scope to represent that difference in grouping. It was frustrating. I had to take the little cap off the scope, use the screwdriver to move a click or two, sometimes more, then screw the cap back on. No, that does not build character. At my age it just made me anxious thinking it was maybe me and not the ammunition. My vision and sensory-motor reflexes are not the same as 50 years ago. Maybe the stories about old age are true?
His research confirms that the impact point will change when ammunition or load recipe is changed. The real question is “How much change can we make and still keep the impacts inside the tan regions at 100 yards.
The best and most effective path for this determination is to shoot other suitable hunting ammunition and determine which, if any, meets the impact area criterion. Guess what, following this advice leads to more trigger time and fun at the range!
Be sure to look over the Hunting Zero discussion for a more specific discussion of a method to apply the principles discussed here.
About the Authors
Allen J. Schuh, Ph. D. is a retired college professor. He received his academic degrees in Psychology: A. B. 1963 San Diego State University, M. A. 1965 University of California, Ph.D. 1971 Ohio State University. During the 1960s he served in the US Navy. During service was a range officer for two years and qualified Navy Expert Pistol Shot with the 1911A1. He has published several dozen scholarly papers, nine patents, and a textbook. He maintains membership in scholarly and professional associations including: American Psychological Association, Association for Psychological Science, Institute of Operations Research and Management Sciences (INFORMS), and American College of Forensic Examiners International (Psychological Assessment).
Joseph Smith is a retired mechanical engineer who devoted several decades to research in weapons effects and weapons development at both the Air Force Armament Laboratory at Eglin AFB in Florida and at the Lawrence Livermore National Laboratory in Livermore, California. He is an avid shooter and reloader who has competed in the NRA 2700 matches (.22, .38, & .45 bullseye shooting) as well as international style air pistol. Among other things, the competitive shooting resulted in a team national record and the 1973 Arizona State champion in the air pistol. He is a Vietnam Veteran and an NRA Life Member. He has instructed rifle and shotgun skills for Boy Scouts of America shooting sports. He recently retired from the University of California after more than thirty years dedicated to research and development of a wide variety of weapons. Joe currently manages the website ShootersNotes.com focusing on a variety of rifle-related topics.