Define a 1MOA rifle

[Mungo]

I have been approached to do some statistical analysis of load development data. He wants to know if he has a 'true' 1MOA rifle.

I asked him what criteria he'd like me to use to define a 1MOA gun. He couldn't say, and it turns out to be quite hard to find any standard definition online.

So: what would people say is a numerical definition of a 1MOA gun? The options I have at the moment:

1. All shots fall within a 1" circle at 100 yards (that is ALL shots ever fired).
2. Some proportion of shots fall inside a 1" circle at 100 yards. Popular options include 95%, 90% and 80%. However, we also need to specify how many shots we need to shoot to be satisfied that the gun is putting n% inside an inch. This is essentially the 'Circular Error Probable' concept that is commonly used for things like artillery (though here they use 50% as an acceptable threshold).
3. The mean distance of all shots is 0" from the point of aim, but with an SD of some number. However, there is considerable confusion about what the appropriate SD should be. My own simulations suggest that if you're shooting 5 shots groups, you will generally see all shots go inside a 1" circle if you have an SD of no more than 0.3. If you're shooting groups of 10, that drops to 0.2.

What do people think?

 

[stubear]

I think you’re overthinking it - if the rifle generally and on average puts shots on a 1” circle at 100y then it’s a 1MOA rifle. There’s going to be flyers, there’s going to be shots that fall outside that and I think trying to come up with a hard and fast rule is an exercise in futility, because everyone has a different view on acceptable and repeatable accuracy.

Personally the question I would ask is “is this rifle accurate enough to do what I need to do with it?” If it is then you’re set. Job done.

 

[cjm1066]

Zero and grouping need separating.

If it groups 1moa it's likely to vary slightly in point of impact due to operator issues.

 

[takbok]

I think that you both have way too much time on your hands

 

[billgatese30]

Statistically speaking my opinion would be, sample size of at least 25 shots, plot distance of POI to POA (regardless of angular direction) centre to centre. Check for normality and assuming normal distribution then anything outside of +/-3SD can be disregarded as a flyer/pulled shot. If +/-3SD is <1MOA then you have a 1MOA or better rifle. This assumes we are interested in point of aim. If its purely group size regardless of point of aim, then do the above but assume the distance of each shot to be relative from the statistical mean centre point.

Even better would be to use this data to create an IX chart to monitor trends, or in a perfect world have each shooting session considered a subgroup on an XBar chart.


But that would be a data nerds wet dream

 

[Tim.243]

I have been approached to do some statistical analysis of load development data. He wants to know if he has a 'true' 1MOA rifle.

I asked him what criteria he'd like me to use to define a 1MOA gun. He couldn't say, and it turns out to be quite hard to find any standard definition online.

So: what would people say is a numerical definition of a 1MOA gun? The options I have at the moment:

1. All shots fall within a 1" circle at 100 yards (that is ALL shots ever fired).
2. Some proportion of shots fall inside a 1" circle at 100 yards. Popular options include 95%, 90% and 80%. However, we also need to specify how many shots we need to shoot to be satisfied that the gun is putting n% inside an inch. This is essentially the 'Circular Error Probable' concept that is commonly used for things like artillery (though here they use 50% as an acceptable threshold).
3. The mean distance of all shots is 0" from the point of aim, but with an SD of some number. However, there is considerable confusion about what the appropriate SD should be. My own simulations suggest that if you're shooting 5 shots groups, you will generally see all shots go inside a 1" circle if you have an SD of no more than 0.3. If you're shooting groups of 10, that drops to 0.2.

What do people think?

I think scopes and rifles are much better than people shooting them.
A good example

 

[Mungo]

I think you’re overthinking it

I think that's rather the point. I have been asked to do a formal analysis, so I intend to do that properly.

- if the rifle generally and on average puts shots on a 1” circle at 100y then it’s a 1MOA rifle.

But this is my point: what does 'generally and on average' actually mean? What do you consider 'on average' to mean? 8 shots out of 10 inside an inch? 4 groups out of 5 sit inside a 1" circle? People think they know what they mean, but when you press them, they do exactly what you've just done and resort to very vague generalities.

Personally the question I would ask is “is this rifle accurate enough to do what I need to do with it?” If it is then you’re set. Job done.

But this is not the question my client has asked me. They have specifically asked me to measure the accuracy of the rifle, and establish whether it is a 1MOA gun.

If you went to a mechanic and said 'please calculate the fuel economy of this vehicle', and they said 'ah mate, you're overthinking it - turn the key and she goes, job's a goodun', you'd be a bit unimpressed, no?

 

[Mungo]

I think that you both have way too much time on your hands

Do you have specialist skills that people are willing to pay you to deploy?

Do you tell them they've got too much time and income, or do you think about how best to do the job?

 

[Mungo]

Zero and grouping need separating.

If it groups 1moa it's likely to vary slightly in point of impact due to operator issues.

Yes.

But I'm not measuring divergence from point of aim. I'm measuring group size from mean point of impact (ie. each group defines its own centre).

 

[JamesH]

From a rifle manufacturer guarantee point of view they often say that the rifle will put a 3/4/5 shot group within 1 MOA (this might only be once!)
This is very unsatisfactory to me but often what is quoted as the 1 MOA guarantee.

Personally I would like to think a 1 MOA rifle will put a significant majority of shots (75%?) into 1 MOA

 

[Malxwal]

We have to assume rifle and ammo combo, with ammo a constant. It's the combination rather than just the rifle ?

 

[takbok]

Do you have specialist skills that people are willing to pay you to deploy?

Do you tell them they've got too much time and income, or do you think about how best to do the job?

Different strokes for different folks...

If he's paying you then that's a different story, but it still makes the mind boggle that he needs somebody to tell him how accurate his rifle is.

I'm not judging, it just makes me laugh.

 

[Mungo]

If he's paying you then that's a different story, but it still makes the mind boggle that he needs somebody to tell him how accurate his rifle is.

I'm not judging, it just makes me laugh.

Why?

Do you pay attention to your fuel consumption in your vehicles? Do you pay attention to energy usage in your house? I could list an enormous number of things that we all measure (or have measured for us). We largely take it for granted that (a) there is a standard way of doing this, and (b) the equipment being used is doing it right.

By contrast, people on here go on at great length about accuracy, and often spend enormous amounts of time and money attempting to improve accuracy. And yet there appears to be no consistent way of measuring it.

And if someone with an inquiring mind has paid a premium for a gun that is 'guaranteed to shoot 1MOA', they naturally start to wonder what that really means and how you would actually test that.

 

[Mungo]

We have to assume rifle and ammo combo, with ammo a constant. It's the combination rather than just the rifle ?

Yes - assume all other variables kept as constant as possible.

Obviously the accuracy depends a lot on the shooter, so when analyzing the data, you're really asking 'is the rifle + shooter a 1moa set up'.

 

[Mungo]

I think scopes and rifles are much better than people shooting them.
A good example

As a wise man once said 'if your reply isn't based on facts, don't press the button'...

I'm trying to establish some facts here

 

[billgatese30]

Yes - assume all other variables kept as constant as possible.

Obviously the accuracy depends a lot on the shooter, so when analyzing the data, you're really asking 'is the rifle + shooter a 1moa set up'.

Which is why a statistically appropriate sample size is required. Then you can determine flyers which can be excluded from the dataset.

 

[Mungo]

Which is why a statistically appropriate sample size is required. Then you can determine flyers which can be excluded from the dataset.

I’m not a believer in removing outliers from data sets. With large sample sizes, they become informative.

The only time I would do it is if there was a genuine failure with the equipment. In this case, something like a bipod giving way or the target falling over!

 

[Tim.243]

Yes - assume all other variables kept as constant as possible.

Obviously the accuracy depends a lot on the shooter, so when analyzing the data, you're really asking 'is the rifle + shooter a 1moa set up'.

With Accuracy the biggest flaw is the shooter of every firearm proven day in day out all over the world.
Cars don't have "accidents" by themselves well apart from EV's lol
That is why we miss with a 20k Purdy or a £600.00 Rem 700
Both have to be as good as each other and the shooter is the biggest flaw with a number of factors

You can not build the perfect rifle and there is not a person born to match the rifle that is why we miss

Shot guns are the best example as that is where the greatest error occurs it is the person who misses least wins a world title not the gun.

 

[takbok]

And if someone with an inquiring mind has paid a premium for a gun that is 'guaranteed to shoot 1MOA', they naturally start to wonder what that really means and how you would actually test that.

I guess that shooting at a target and measuring group size is way too simple then? Find out how many shots the manufacturer guarantees 1 MOA for, then check if the rifle does that.

The rifle itself is only a small part of the equation accuracy wise so good luck with isolating it.

 

[Tim.243]

As a wise man once said 'if your reply isn't based on facts, don't press the button'...

I'm trying to establish some facts here

The facts are in post #18