We’ve all been there. In fact, we go there on most, if not all, shoots. We miss! (some more than others) After a drive the conversation invariably turns to our performance and we will start listing the excuses for our poor showing. The normal allocation of blame is down to how much lead we failed to give the bird. Sometimes we may claim to have given too much lead. On a rare occasion we will accept we weren’t on the right line or simply shot badly. Have you ever sat down to really think of why you miss though? There are many influencing factors including your ability, experience, correct gun mount, gun fitting, weather conditions, the bird’s ability to change direction, your frame of mind, and cartridge load and size. There will undoubtedly be other reasons but the one I want to chat about today takes us back to school mathematics. (just for 1 period, I promise!) Specifically, trigonometry with the added dimensions of speed and time.
Many shooters will have a preferred cartridge load for different quarries. For example, 36/4 might be used for duck, 32/5 might be considered standard for pheasant, and 30/6 is good for partridge. As most of you will know, the first number is the weight of the load of ball bearing shot which determines how many there are packed into the little cylinder, and the second is the size of the ball bearings from an international standard. There are other specifications to consider however and one of these is velocity. Different manufacturers produce different performance cartridges, and all will have different velocity specifications. This means that once shot the ball bearings, from different brands and model of cartridge, travel at different speeds to their target. We all know that the faster an object travels the quicker it reaches its destination. So different cartridges will perform slightly differently. Furthermore, as the shot travels it loses its energy, so its speed decreases the further it goes. This decrease can be as much as 50% at 40 yards. Some commonly used cartridge brands (muzzle) velocity specifications (in feet per second - fps) are as follows:
- Hull, The Partridge Cartridge (12 Gauge) 1410 fps
- Hull, Driven Grouse (12 Gauge) 1450 fps
- Hull, High Pheasant (12 Gauge) 1450 fps
- Hull, High Pheasant Extreme (12 Gauge) 1400 – 1450 fps (dependent on load and shot size)
- Hull, Driven Grouse (20 Gauge) 1430 fps
- Hull, High Pheasant (20 Gauge) 1430 fps
- Hull, High Pheasant Extreme (20 Gauge) 1360 – 1430 fps (dependent on load and shot size)
- Gamebore, Black Gold (12 Gauge) 1450 – 1500 fps (dependent on load and shot size)
- Gamebore, Black Gold (20 Gauge) 1425 – 1475 fps (dependent on load and shot size)
- Churchill, Hellfire Cu (12 Gauge) 1425 fps
- Churchill, Hellfire Cu (20 Gauge) 1350 – 1400 fps (dependent on load and shot size)
- Eley, VIP (12 Gauge) 1450 fps
- Eley, Gran Prix High Pheasant (12 Gauge) 1425 fps
- Eley, Classic Game (12 Gauge) 1350 fps
- Eley, VIP Game (20 Gauge) 1375 – 1400 fps (dependent on load and shot size)
- Eley, Gran Prix (20 Gauge) 1325 fps
We can see from the table above that the range of velocities is pretty wide. As a basic rule, having a bag of assorted cartridges will do nothing to assist consistency throughout a day’s shooting. In addition to the velocity specifications cartridges have patterns and load parameters to consider. These become important when we look at the penetration power of shot required to cleanly kill a bird – how often have you seen a bird ‘absorb’ the shot and continue to fly? You should have a better understanding of why this occurs when we look at the difference in the lead to kill point intersection numbers in the next paragraph.
I said at the start of this article we were going to return to school and apply trigonometry so let’s do that now.
Looking at the image below, if the shooter is at point A, and the intended destination of the shot is point B, what is at point C? That’s easy, it’s the start position of the bird. The problem is, it’s moving all the time (or should be!) and so we need to take its speed into consideration. How fast do our game birds fly? Are partridges quicker than pheasants? What about duck and geese? The list below shows some of our most common quarry in order of speed performance. These figures are the average fastest speeds in no wind conditions (i.e. they aren’t slowed by a headwind and aren’t assisted with a tail wind). Unfortunately, the conditions are always changing so we can only use these values for explanation purposes.
- English Partridge 45 mph / 66 fps
- French Partridge 40 mph / 59 fps
- Pheasant 56 mph / 82 fps
- Pigeon 37 mph / 54 fps
- Grouse 52 mph / 76 fps
- Woodcock 30 mph / 44 fps
- Snipe 60 mph / 88 fps
- Mallard 55 mph / 81 fps
- Teal 32 mph / 50 fps
- Canada Goose 60 mph / 66 fps
To denote our shooter, bird, shot placement parameters into a triangle for representative purposes I have drawn the relationship between the points as shown here:
Applying the formula shown below therefore, a pheasant is travelling from point C to point B at its average maximum speed of 82 fps and from the time we see it to the time we mount, swing and pull the trigger is approximately 3 seconds then the bird will have travelled just over 240 feet. The distance from the shooter to the intersection point is in the region of 170 feet. Using a cartridge with a velocity of 1350 fps the shot will arrive at the intersection point in 0.13 seconds. If the shot velocity was higher at say 1500 fps, then it would only take 0.11 seconds, so the difference is only 0.02 second. However, a pheasant can cover 1.64 ft in that time.
This brings us back to the shot pattern point from earlier. Shooting at a 40-yard (120 ft) pheasant our shot will have travelled further than 40 yards and lost over 50% of its power. The shot pattern will have spread to something in the region of 30 inches dependent on the chokes used so the 1.64 feet / 20 inch difference based on cartridge choice won’t really affect hitting the bird but there could be a chance that not enough shot with enough energy will be available to kill the bird.
To add another value into this ever increasingly complex calculation, we need to consider the force required to kill a bird humanely. For the majority of our game birds it is accepted that a pellet needs to have 0.8 foot pound (ft lb) of energy to penetrate and kill the quarry. This increases to 1.5 ft lb for our larger birds such as geese and is slightly lower for our smaller species such as woodcock. The formula to calculate this is complicated so you will have to trust me when I say that a single No.5 pellet with a muzzle velocity of 1350 fps has a ft lb value of 8.1. This is over ten times the value required. However, this is its value at the start of its journey and it’s also based on the velocity quoted by the manufacturer. In reality the actual measured velocity is less than the specified muzzle velocity and its energy reduces as it travels. A target at 40 yards will see the velocity of the pellet reduced by something like 50% thus resulting in a ft lb value closer to something between 0.7 and 2, dependent on the actual velocity. This is where the pattern becomes important. We need to try and ensure the bird is hit by a number of pellets in a close pattern so the more accurate the shot, with an appropriate choke, the more likely the chances of a successful clean kill.
What I’m sure you are asking now is “how much lead therefore do I need to give to hit the bird?”. Due to the many external factors affecting our mathematics it’s not an easy question to answer. In conditions where there is no wind and the birds are flying at their maximum speed, the cartridge velocity is as specified and doesn’t lose energy as it heads towards its target at say 40 yards, then we can calculate the distance you need to be in front. However, the key relationship in this scenario is between how long the shot takes to get from the shooter at point A to the kill point at B and where the bird is when the trigger is pulled. This distance will change dependent on when you pick up the bird and where you decide to ‘set’ your kill point. A crossing bird for example is likely to have a longer A-B distance than a bird flying directly overhead. Let’s use the distances in the image above. We know a pheasant at full speed is flying at 82 fps and it takes the shot 0.13 seconds to arrive at the kill point if the velocity is 1350 fps and the distance between point A and B is 170ft. We can also calculate that the pheasant can cover 10.66 ft in 0.13 seconds so that’s the lead we need to have in order for the bird to arrive at the kill point at the same time as the shot. If we add a little bit of reality into the calculation however and accept that the actual velocity is less than the specified and that the shot decelerates as it travels then our distance will increase as the shot will be travelling slower and take longer to get to the kill point. Similarly, the bird might not be at full speed and will take longer to cover the same distance meaning less lead is required.
Well, now you know a little more of the science that often leads to our frustration. Of course, nothing beats practice, so get down to the clay range as much as you can before the season starts. Hopefully though this short overview of speed and distance gives you some appreciation and understanding of what you need to do to accommodate the competing factors when taking the shot. However, we all like to challenge ourselves that is why we continually want to shoot difficult birds but please make sure you only shoot birds you know you are capable of killing cleanly. Good luck!