Define a 1MOA rifle

[Malxwal]

I found this:
A 2008 United States military market survey for a Precision Sniper Rifle (PSR) calls for 1 MOA (0.3 mrad) extreme vertical spread for all shots in a 5-round group fired at targets at 300, 600, 900, 1,200 and 1,500 meters.[25][26] In 2009 a United States Special Operations Command market survey calls for 1 MOA (0.3 mrad) extreme vertical spread for all shots in a 10-round group fired at targets at 300, 600, 900, 1,200 and 1,500 meters.[27][28] The 2009 Precession Sniper Rifle requirements state that the PSR when fired without suppressor shall provide a confidence factor of 80% that the weapon and ammunition combination is capable of holding 1 MOA extreme vertical spread.

 

[Twodogs]

Chapter one, Understanding Dispersion, Modern Advancements in Long Range Shooting, Volume ll, Brian Litz is a fascinating read regarding precision and various methods as to how to measure it.

 

[billgatese30]

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!

Thats fine, in which case you I would have said that you will need the entire dataset to be <0.5MOA of the group centre to qualify. However in a normal distribution 6 standard deviations represents 99.9997% of the estimated population which by definition means that pretty much any shot outside of this is highly irregular and most likely due to special causes (such as shooter, wind or ammunition influence) and not common cause (i.e. The rifle we are evaluating just being inaccurate).

How many shots would you be firing to generate the dataset?

 

[Lateral]

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?

But you’d also be asking a question way too simple to give an answer to, because fuel economy can only be measured at a given speed/load, hence car manufactures attempting to give fuel economy at three different speeds, and we know that is unreliable.

IMPO, the accuracy of a rifle has to take into account user error, and ammunition fliers, because that’s part of the reality.

And that just measuring at 100yds/m, does not make a 1”/1moa, rifle, because to me, it needs to repeat that accuracy across any distance the rifle will be shot, and we know that whilst we hope it is, there’s no guaranty the accuracy will be linear at 100, 200, 300 etc’.

So at the very least, the owner should state the maximum distance they will shoot, and in an ideal world, the rifle accuracy tested out to that distance.

 

[shakey jake]

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?

If this is your specialist skill and your charging, what our cut for helping work it out?

 

[Tim.243]

Load testing a few years ago. First 3 shots @ 100 yds .270 rem 700 150gn head
First 2 shots were the ones touching, third I said to @paul o' I pulled it a bit.
so the human factor was the error as I could not repeat the other 2.
Fact...

 

[WalkedUp]

Coming from a technical and academic background this thread is of an intellectual interest from me. Before any accusations of Willy waving, I am not a good shot and have no interest in being a better shot or getting a better rifle etc. I work to MoF (Minute of Fox).

First, there does not seem to be an agreed standard. So let’s define a SD100-1MoA standard.

There will be many factors in this that create variation and so need to be defined. For illustration: some are environmental: wind, barrel temperature etc. Some are operational: using a 4 magnification scope, or a 4” black bull will create user deviation. Then you need to define range. Doing this test at 3 yards is not practical nor is it at 3,000 for e.g. 22LR.

Next there needs to be limits for practicality, otherwise it would be impossible to define a rifle’s accuracy until it has been disposed of. So is 1,000 shots a reasonable set? Probably excessive. Is two shots enough? No.

Any rifle will eventually put three rounds on top of each other. Something has to be able to consistently perform with repeatable results. Every time it produces X. Finally you need to give an allowance for flyers otherwise a single and very rare bad round etc will black list a rifle.

For example: “the SD100-1MoA standard defines the ability for a rifle set up from any loose position (not clamped) to fire 4 bullets from 5 shots within 1.04” at 100 yards. A rifle that achieves this standard 5 times in succession can be designated a SD100-1MoA rifle.”

 

[Mungo]

The facts are in post #18

Ok - so say you wanted to measure the accuracy of you plus your set up. How would you do it?

Actually measure, not just get a rough idea.

 

[Mungo]

I guess that shooting at a target and measuring group size is way too simple then?

How many shots? How many groups?

That is the simplest approach, but you still need to decide what sample size you want to use. The more shots you take, the larger the group will be. If I simulate groups assuming a vertical error of 0.5 and a horizontal error of 0.5, three shot groups return an extreme spread of around an inch, . But for 10 shot groups, ES goes up to around 2".

Find out how many shots the manufacturer guarantees 1 MOA for, then check if the rifle does that.

As you know, they usually specify 3 or 5 shots. But that's quite easy to meet, and does not actually measure the accuracy of the rifle. That's like saying 'this car goes at least 60mph'. It doesn't tell you how fast it COULD go.

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

Oh absolutely.

But the question remains: if you want to actually measure the accuracy of a rifle + shooter, how do you do it?

 

[Tim.243]

Ok - so say you wanted to measure the accuracy of you plus your set up. How would you do it?

Actually measure, not just get a rough idea.

No point as you would dismiss my idea (s) until proven wrong.

Put the action in a sled but again there is room for error.

Manufactures test things to destruction then work backwards, everything has a tolerance and fail point.


Other factors will be breaking in a rifle "who decides that" more snakes in the basket...
Who loads the rounds "did you make a mistake? "

 

[Mungo]

Coming from a technical and academic background this thread is of an intellectual interest from me. Before any accusations of Willy waving, I am not a good shot and have no interest in being a better shot or getting a better rifle etc. I work to MoF (Minute of Fox).

First, there does not seem to be an agreed standard. So let’s define a SD100-1MoA standard.

There will be many factors in this that create variation and so need to be defined. For illustration: some are environmental: wind, barrel temperature etc. Some are operational: using a 4 magnification scope, or a 4” black bull will create user deviation. Then you need to define range. Doing this test at 3 yards is not practical nor is it at 3,000 for e.g. 22LR.

Next there needs to be limits for practicality, otherwise it would be impossible to define a rifle’s accuracy until it has been disposed of. So is 1,000 shots a reasonable set? Probably excessive. Is two shots enough? No.

Any rifle will eventually put three rounds on top of each other. Something has to be able to consistently perform with repeatable results. Every time it produces X. Finally you need to give an allowance for flyers otherwise a single and very rare bad round etc will black list a rifle.

For example: “the SD100-1MoA standard defines the ability for a rifle set up from any loose position (not clamped) to fire 4 bullets from 5 shots within 1.04” at 100 yards. A rifle that achieves this standard 5 times in succession can be designated a SD100-1MoA rifle.”

Exactly that.

And then anyone advertising a rifle can actually state that as a valid point of reference.

 

[tackb]

remove any human interference so you need a repeatable shooting device

stick to 100yds as environmental influences are reduced as much as possible

the rifle then needs to group into 1'' centre to centre consistently for your sample size , presuming you are monitoring temp etc

i'd want to see 10x10rd groups to call the rifle a 1 moa rifle , where the group is on the target is irrelevant.

i don't envy you the task because eliminating variables will be a nightmare

 

[nun_hunter]

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'.

I would say you need to remove the shooter from the equation in order to test the accuracy of the rifle. Barrelled action in a solid vice.

Use factory ammo that is as consistent as possible to try and remove any variations there. All components only used once.

For a hunting rifle I would deem the first 3 shots fired from a cold and clean barrel must all land within 1".

The parts you can't control precisely are the added wear on the rifle between shots and the level of fouling between shots. I expect replicating the cleaning regime would be difficult when you're measuring things so accurately as would be any variation caused by barrel wear or fouling between each shot.

If it's a target rifle then I would expect the groups to be 10 rounds.

Lastly the bullet choice should be of a design and weight to measure groups out to 300 yards at least to ensure the groups were still 1moa at ranges for expected use of a hunting rifle.

As previously mentioned, rifle manufacturers who say 1moa guaranteed means (at least I believe this is what they mean) that they shot a single group on at least one occasion at 100 yards and the 3 bullets all struck the target within 1" of each other.

 

[Mungo]

No point as you would dismiss my idea (s) until proven wrong.

Why would I?

You're an engineer. You deal daily with measuring tolerances and ensuring precision.

What, to you, would be a robust way to measure the accuracy of a given set up?

 

[Mungo]

remove any human interference so you need a repeatable shooting device

stick to 100yds as environmental influences are reduced as much as possible

the rifle then needs to group into 1'' centre to centre consistently for your sample size , presuming you are monitoring temp etc

i'd want to see 10x10rd groups to call the rifle a 1 moa rifle , where the group is on the target is irrelevant.

i don't envy you the task because eliminating variables will be a nightmare

Thanks.

You say 10X10rd groups.

Would all 10 groups need to be under 1"?

The reason I ask is that when I run simulations, for this to be satisfied, the x and y error need to be very small (having an SD of 0.1). I don't think very many rifles would satisfy this. The CEP for a set up that satisfies this would need to be 0.1".

 

[NoIDeer]

As Mark Twain famously said there are lies, damned lies and statistics. More useful is the phrase 'minute of deer'.

In my opinion a shooting system is only as accurate as the whole thing shooter and shooting platform, if it doesn't put every bullet into the kill zone then it's no good.
If you have to measure that then I would use some form of mode average, measuring the number of bullets into say 1 moa, 2 moa... allowing a maximum outlier.

I've got two 1 moa Sakos and a pet unicorn.

 

[Tim.243]

Why would I?

You're an engineer. You deal daily with measuring tolerances and ensuring precision.

What, to you, would be a robust way to measure the accuracy of a given set up?

Bench rest rifle sled

 

[billgatese30]

How many shots? How many groups?

That is the simplest approach, but you still need to decide what sample size you want to use. The more shots you take, the larger the group will be. If I simulate groups assuming a vertical error of 0.5 and a horizontal error of 0.5, three shot groups return an extreme spread of around an inch, . But for 10 shot groups, ES goes up to around 2".

10 shots is still too small of a sample size in my opinion.

As I stated above, 25 is generally accepted as the minimum for a statistically appropriate sample size, but if you could go to 50 or 100 then even better, as this will allow you to predict the population standard deviation more accurately than you could from a smaller sample. However increasing the sample size is a law of diminishing returns in its ability to accurately predict the population SD and of course we would have other factors such as barrel cleanliness coming into it as well.

Eliminate what variables you can or reduce as far as practicable (wind/ammo variation/barrel temperature varianxes etc), then shoot a statistically significant sample size, assess for a normal distribution, then remove outliers of >3SD either side of the estimated population mean. This is generally accepted as good statistical practice unless there are strong practical reasons for deviating.

Also just to clarify, I've done this subject as a career for over 20 years for multi billion dollar manufactures of everything from specialist batteries to medical devices. I'm a process control subject matter expert and a six sigma black belt (for what its worth).

 

[Mungo]

Bench rest rifle sled
View attachment 391793

Agreed - that's undoubtedly the best physical set up.

But then how do you measure the resulting accuracy?

Assume someone has done this. They have a stack of targets with holes in. How do you establish the accuracy of that set up?

 

[Tim.243]

Agreed - that's undoubtedly the best physical set up.

But then how do you measure the resulting accuracy?

Assume someone has done this. They have a stack of targets with holes in. How do you establish the accuracy of that set up?

Testing and more testing then more testing same a manufactures spend huge amounts on.
Any way I am going foxing later to test myself against oh slippery one. Good luck