Article 7 – 2024 (August)
Australian Shooter Magazine
Question and Answers
Article 7 – 2024 (August)
Question: I get very confused by much of the firearm terminology, but I feel I am slowly getting a better understanding of it. I really want to start shooting Sporting Clays seriously once I finish University and I am looking at buying a shotgun that is specifically made for this task. I have read many of your previous articles in ASJ and going with your advice I have narrowed my choices down between a second hand Miroku MK 60 Grade V and a Beretta DT 10. Both are Sporting models and after much deliberation I have decided on eighty one centimetre barrels.
What I need to get my head around is the difference between the point of aim of these two guns as opposed to their point of impact. In layman’s terms can you explain the difference in this terminology.
Grant Bradshaw, Kangaroo Flat VIC
Answer:
Both are great shotguns and I am sure either will get you off to a great start in our sport.
Your question regarding point of aim and impact is a good one and it needs to be clarified as an understanding of it is essential if you are to perfect where you want your shotgun to shoot.
Let me explain it on the assumption you can get access to a pattern board. Every decent shooting range should have one of these. Ideally the bottom of the board should be about 1.2 metres off the ground. A good size pattern board is approximately 1.2 metres wide and 1.5 metres high.
Go back twenty metres and mark a spot on your pattern board pretty much in the centre. This spot will become your point of aim. Fire a shot at the board and let’s assume your shot imprint is forty centimetres in diameter. I will assume it is dead straight, but 30 centimetres of it is above the point of aim and 10 centimeters is below. This equates to seventy five percent hence this shot pattern is called a 75/25 pattern (25 percent below the point of aim). This percentage will stay the same at all distances until gravity starts to affect the shot payload.
The point of impact for this shot can be referred to as a numeric measurement also and this will vary with distance. The point of impact for this shot can be referred to as “10 centimetres high at 20 metres”. At forty metres it will be 20 centimetres high and at 60 metres the point of impact for this firearm can be referred to as 30 centimeres high, but once again the pattern percentage of 75/25 will remain constant until the shot starts to lose its battle with gravity and it will become lower. Bigger shot sizes obviously hold their energy at distance for longer.
Your point of aim should not be a variable, but the point of impact will vary from shotgun to shotgun largely due to the configuration of the stock and how it allows your eye to look down the barrel. Different brands of ammunition will throw different diametre shot patterns due to a variety of factors that include velocity, wad configuration and even quality and size of shot, but I have never patterned a shotgun that throws a different point of impact based on a brand name. Testing the actual quality of your ammunition can become much more complex task and will involve counting shot strike percentages and as a general rule this is done at forty yards. This becomes a different topic altogether.
Different disciplines of shotgun shooting generally require your shotgun to have a different points of impact. As a general rule the slower disciplines of Trap have the higher points of impact whilst shooters in the field generally prefer points of impact that could be as low as zero or that can be referred to as a 50/50 pattern. Trap shooters always shoot at a constantly rising target, whilst in the field you may be face game birds that are falling to the earth quickly therefore there is an advantage that a lower impacting shotgun will give you in terms of accuracy. I would never recommend anyone have a point of impact for any shotgun, regardless of what you are using it for, to have a point of impact lower than this.
I hope this helps you understand the terminology that is often mistakenly referred to as the same, but in reality, they can be vastly different.
Find a pattern board or do this exercise safely using some cardboard nailed to a tree or a couple of posts. Shotgun shooting is no different than rifle shooting. If your new shotgun has an adjustable comb on it then making these point of impact adjustments to find the perfect shot pattern for you is very easy.
Know where your firearm is impacting and you are well on your way.