Minute of Angle, MOA, or even sub-MOA are phrases that are thrown around a lot, but the vast majority of people have it all wrong.
This is because the MOA is usually referred to as an imperial measurement, which is one inch at 100 yards. This is the first mistake. It is not one inch. Secondly people forget to calculate the difference between 100 yards and 100 metres.
To quickly cover the science: The word ‘minute’ is a way of referring to 1/60th of something. For example, one second of one minute is 1/60th of that minute. One minute is 1/60th of one hour and so on.
When we are talking (one) Minute of ‘Angle’, the size of the angle we are referring to is one degree. In other words, MOA = 1/60th of one degree.
The following description is courtesy of Gun University. The figures are in imperial measurements, but it works for this explanation:
‘Imagine holding two laser-pointers in your hand and pointing them at a target 100 yards away. Now, if you spread those two laser pointers apart at a certain angle, the lasers’ dots on the target will spread further apart.
‘If the laser-pointers were spread apart at a 45-degree angle, the dots would be very far apart at 100 yards. However, if the laser pointers were spread apart at a small angle, let’s say 1/60th of one degree (one MOA), then the laser pointers’ dots would be about 1 inch apart.’
By the way, one MOA is just called ‘MOA’: the numeral ‘1’ is dropped when referring to a single Minute of Angle.
MOA is actually 1.047 inches at 100yds (not one inch as is often thought).
Convert 1.047 inches to mm = 26.5938mm.
Multiply this by 1.0936 to go from 100yds to 100m = 29.083mm.
So MOA at 100m is 29.1mm (with rounding).
I fully appreciate that this is a difference of approximately four millimetres from the rough calculations of an inch to mm, as one inch = 25.4mm, but it is more significant and relevant than you may think. It has to do with the effect this has on the shooter’s confidence ‑ a key contributing factor towards how accurate a shooter is.
Many years ago, I was away on a hunting trip. I had taken a freshly-licensed novice shooter with me. I asked what his new Tikka .233 rifle was zeroed at and received a blank stare in reply. No problem. He was a good bloke and eager to learn so I was happy to share with him whatever knowledge I had.
I set up a target at 25m so he could start the zeroing process by firing three shots in each group. I pushed it out to 50m and then finally to 100m to complete the task. This is when I joined in to check zero on my Ruger .223. His groups were very respectable around the 55mm mark** (which we now know is less than 2 MOA).
I was still rating groups under the incorrect assumption that MOA was 25.4mm at 100m. I shot group after group in the high 20s but could not break the ‘one-inch barrier’ which frustrated me no end. At one point, my mate turned to me and asked: “Is there some sort of special ‘MOA Christmas party’ which you’re trying to land an invite to?” I laughed and immediately felt better about it. We went on to have a successful and fun trip.
On the drive home I began thinking about the figures involved, which eventually led me to ring my long-suffering brother who is much better at maths than me (but much less enthusiastic about the topic) and he confirmed the number at approximately 29mm for MOA at 100m. At silly as it sounds, suddenly I felt like I’d had a breakthrough.
From that day on I was comfortably able to take eight or nine rabbits out of 10 shots at 200m-plus with this rifle/ammo combo. I’m not relaying this as any particularly brilliant marksmanship, but only to show that once I felt like I was shooting better with what was a budget rifle and factory ammo combination, I actually started to do so.
I’ve included some 100m groups in the attached photographs with a 20 cent piece for reference. Australian 20 cent coins are approximately 28.7mm in diameter, so close enough to MOA at 100m. This shows some sub-MOA and some not sub-MOA groups. I’ve also included one ‘miracle’ group of around .05 MOA shot at 200m with my .30-06 at the range. My mate Thommo was with me so I have a witness, but I’ve never been able to repeat it.
To calculate MOA at various ranges (using 29mm as the rounded down MOA dimension):
MOA at 200m is 29mm x 2 = 58mm.
300m is 29mm x 3 = 87mm.
400m is 29mm x 4 = 116mm, and so on.
That 0.5 MOA 200m group steered me down the path of longer-range shooting. I began to spend lots of time at the range calculating holdover for 300m, 350m, 400m, 450m etc. I imagined myself taking game at more than twice these distances.
But then I started to understand about flight times and downrange winds and a whole bunch of other factors. The flight time of virtually any centrefire projectile travelling at say 2500 feet per second, at 1000m is around 1.3 seconds. That’s long enough for a deer to be in its second stride by the time the round hits.
Then there’s the wind to consider. The further you are away from the target, the less you know about the wind immediately around the target. With no lovely tell-tales fluttering away like they are at the shooting range to help you out, the average shooter is guessing at best. It goes without saying that it is completely unethical to take shots at game at these types of ranges as wounding is a much more likely outcome.
This brings me to the question, ‘How far is too far to shoot?’ The answer to this depends on many factors such as the shooter’s ability, the accuracy of the rifle, the conditions, the quality of the rest and more.
I recently heard it summed up perfectly by American hunting author and TV host Steven Rinella, who said: “If you aren’t completely confident of humanely killing game at the range you’re shooting at, it is too far for you.” For me, I consider anything beyond around 200m to be a long shot which I will avoid if I can. This is despite having good quality equipment, lots of regular practice, a pretty thorough understanding of ballistics and accurate range determination via a rangefinder.
I suspect that there are plenty of shooters out there who if they are being honest with themselves would be in the same boat. It isn’t your shooting that you need to worry about improving, it’s your hunting skills. Learn and practise stalking to within your comfortable shooting range and forget about the ‘MOA Christmas party’. The confidence boost I gained when I discovered I had a MOA rifle was nothing compared to the thrill of stalking in close and putting game on the ground. I guarantee you will find it extremely rewarding.
I shot a South African impala, (roughly similar in size to a fallow deer) at 80m with a full-length timber-stocked .308. This rifle looked to me like a semi-ancient relic, topped with an equally antiquated-looking fixed 6x scope. This combination was flat out keeping 3 MOA in my hands.
But as the impala was shot at a range of 80m, and with 3 MOA being around 70mm at this distance, I aimed for the centre of the shoulder-ball, the shot easily hit the engine room and the animal piled up quickly.
** A 50mm group at 100mm is roughly 1.7 MOA. For hunting, 1.5-2 MOA is more than adequate. 2 MOA would equate to a 116mm ring at 200m which is easily sufficient to place a fatal round into the vitals of a deer, pig or even a fox.