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What is a half MOA rifle?

#51
Re: What is a half MOA rifle?

Is this thread about the rifle or the shooter and the rifle? The title of the thread doesn't match the discussion (or maybe that was the point). A half MOA rifle is a rifle <span style="font-weight: bold">capable</span> of shooting half moa.
 
#52
Re: What is a half MOA rifle?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">If you measure the distance to the outside edges to the two most widely separated shots, you just subtract one bullet diameter to get the center-to-center distance. Either way is correct.
</div></div>

Or, if you have a digital caliper, you can just zero it on a bullet and measure directly. No need for the subtraction.
 
#53
Re: What is a half MOA rifle?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MontanaMarine</div><div class="ubbcode-body">A rifle that can hold half moa accuracy "all day long"....When the shooter "does his part".......grin</div></div> +1, Just that simple.....Well, the post, not the act of it.
wink.gif
 
#54
Re: What is a half MOA rifle?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MontanaMarine</div><div class="ubbcode-body">I like to know that I am the weakest link, not my equipment. </div></div>

Exactly.

It's hard to work on MY skill if the limiting factor is the equipment. However skill is what matters. A 1/4 MOA rifle doesn't matter for shit if you can't call wind or you mash the trigger.
 
#55
Re: What is a half MOA rifle?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LoneWolfUSMC</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MontanaMarine</div><div class="ubbcode-body">I like to know that I am the weakest link, not my equipment. </div></div>

Exactly.

It's hard to work on MY skill if the limiting factor is the equipment. However skill is what matters. A 1/4 MOA rifle doesn't matter for shit if you can't call wind or you mash the trigger. </div></div>

Good luck finding any safe rifle with a bore that isn't a frosty mess that can't shoot better than the majority of shooters, here or elsewhere.

The day that I can outshoot my equipment, I'll send it to GAPor someone else. Until then, I'm sure my stock "porn star" FN barrel will have to do.
 
#57
Re: What is a half MOA rifle?

Most MOA rifles on the internet are based on the keyboard the person is using.......so therefore if I get a new keyboard my old beat up rifles will become sub MOA at a kajillion yards
smile.gif
. And as usual, the best thing to do at your local range is to walk in, state you have a MOA rifle (pronounced- MOE WAH) and want to show the boys how they should be shooting like you do. THEN RUN LIKE HELL. LOL OK, Sorry for the funnies.
 
#58
Re: What is a half MOA rifle?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: palma</div><div class="ubbcode-body">Is this thread about the rifle or the shooter and the rifle? The title of the thread doesn't match the discussion (or maybe that was the point). A half MOA rifle is a rifle <span style="font-weight: bold">capable</span> of shooting half moa. </div></div>

You shoot enough groups with any rifle and you will find it <span style="font-weight: bold">capable</span> of shooting half MOA. I have shot exactly 2 groups below half MOA with my 22 at 100 yards. Is it a half MOA rifle? It averages about .8 or .9 at 100, so I would say not.

I have a sporter 270 that I have shot a few groups under 1 MOA. Is it sub-MOA? I would say not. It averages closer to 2 MOA.

A lot of people look at the smallest group they have ever shot with a rifle and assume that the group is what the rifle is capable if they did everything right every time. This simply is not the case.

Of course, these types of arguments always devolve into the shooter versus the gun type arguments and it is pretty hard to separate the two... a gun always needs a shooter and vice-versa. It was remarked earlier on that there aren't many half-MOA shooters around and I disagree. I think the rifle/ammo tends to be the weak link to a point for 100 yard center-fire where wind isn't really a factor.

IMO (and I could be pretty wrong on this), someone who actually works to develop their marksmanship skills can shoot pretty well under zero pressure and no time limit at a known [short] distance. The great shooters are the ones that can shoot consistently well under pressure, when rushed, when forced to shoot out of position or out of their element. Further, a great shooter will know how to read wind and range and dope accordingly. These things have nothing to do with small groups at 100 yards.

But what makes for a good shooter is highly subjective anyway. A good benchrest shooter will be very different from a good across-the-course shooter, who will be very different from a good field shooter (what most people call tactical shooters and hunters). A good benchrest shooter probably won't be able to shoot that great offhand. A good across-the-course shooter probably won't be able to get the tiny groups that a benchrest shooter can work out. And neither of those could do that great at shooting at unspecified ranges like a field shooter. There are cross-overs, but there are different shooting disciplines for a reason. It is hard to be good at them all. Not really enough time in a day.
 
#59
Re: What is a half MOA rifle?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: MontanaMarine</div><div class="ubbcode-body">I had one that was horribly inaccurate, and obviously the weak link. It was an SKS. It would hold about 6 moa at 100 yards, and no it didn't "tighten up" downrange......grin </div></div>

I would suspect this had more to do with the economic system in the country in which it was produced (socialism) than the design of the rifle itself.

Sure, some commie piece of shit doesn't hit. But find me a $500 savage that won't shoot 1 MOA with the right ammo and I'll be really shocked. Even a $500 AR can do that.

Sure, $4000+ bolt guns have their place...but it's just a tube with a cap on the rear in the end. It's the driver that aims that tube where it belongs that really matters. Sure, some hardly measurable amount of mechanical accuracy is gained by cutting a tighter chamber with a shorter leade, developing loads perfectly, and truing the action. But I'd submit that the overwhelming majority of button rifled, mass-produced, long leade, factory stock rifles are capable of 1 MOA accuracy all day long. Sure, some are not, but in the days of CNC machining, these are clearly the exception, not the rule.

I'm not saying there is no use for a Robar, GAP, White Oak, etc. What I am saying is that the difference between those and a Remington off the line is that the absolute best of shooters can decipher a difference at the margins. The rest of us pee-ons are lucky to hit the target.
 
#62
Re: What is a half MOA rifle?

If i'm reading that article correctly, what it's saying is that say if my rifle averages .600" groups at 100m, then it's normal for it to go as low as .25, or as much as .8", but that that range doesn't indicate that there is necessarily a problem with the rifle, shooter, or load. Am I correct in that thought?

Branden

BTW, thank you for posting that article. As long as i'm interpreting it correctly, it makes me feel better about my performance today, which was lousy for the most part, but I do have excuses, it was my fault, period.
 
#63
Re: What is a half MOA rifle?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Dust_Remover</div><div class="ubbcode-body">If i'm reading that article correctly, what it's saying is that say if my rifle averages .600" groups at 100m, then it's normal for it to go as low as .25, or as much as .8", but that that range doesn't indicate that there is necessarily a problem with the rifle, shooter, or load. Am I correct in that thought?

Branden

BTW, thank you for posting that article. As long as i'm interpreting it correctly, it makes me feel better about my performance today, which was lousy for the most part, but I do have excuses, it was my fault, period.</div></div>

That is correct. Although, if you fire a bunch of groups on a single day that are wider than your long run average, that might indicate an issue, then again, it might not... clear as mud, right?

I took a statistics class once and the professor asked several students to draw a random pattern on the board... every single student alternated high and low dots on the board. The professor pointed out that one of the greatest capabilities of humans is to detect patterns. As a result, if we see something happen, such as prices to rise in real estate five years in a row or for us to get five consecutive good (or bad) groups in a row, we tend to sense a pattern and thinks something is going on, when in fact, it is just random statistical variation.

This is why it is important to log every shot... you want to see if something you are doing results in a change in your long run average (be it different ammo, different shooting technique, etc.). And also why you shouldn't dump a target because you "weren't shooting well that day" (I am guilty as charged).

Statistically, a sample size of thirty starts to give you good results (I don't want to get into the math, but the standard deviation of a sample tends to underestimate the actual standard deviation of what you are testing. The degree to which you need to correct for this plateaus at around 30 samples). Thirty 5-shot groups is a lot of groups. More than most people shoot at a single range session. Unfortunately, over several range sessions, we will tend to blame different things for poor or good performance. This is not to say that there aren't actual variables that change over these sessions that may actually affect groups size.

And so there is the big quandry about using statistics with shooting. You might find that nothing you are doing is making a difference OR by the time you have figured out whether you are doing something that makes a different, you have shot your barrel out. You have to walk a thin line.
 
#64
Re: What is a half MOA rifle?

His conclusion:
"If you want to test the long-term group size of your rifle, I suggest that you shoot three 5-shot groups and take the average. This average will give you the true value, plus or minus 25%, 95% of the time"

meaning the average of the three five shot groups will be pretty close to the accuracy of you and your rifle.
 
#65
Re: What is a half MOA rifle?

My shooting today wasn't that great, however it wasn't horrendously horrible either. I do my best to call every shot, and my first 4 groups weren't good. However there was a significant change on the way that the rifle was held, rested, and recoiled. When I went back to the bipod, and a good bad setup on the rear, my groups shrank by close to half. It was only shooting ~1" groups initially, then down to .6's on my amax's, then I went back to Hornady 168 match and out of the 3-5shot groups the first group got the first 2 virtually in the same hole, then the 3rd shot I didn't follow through on and it dropped low and right. 4th shot with the first 2, then the 5th shot I screwed up the follow through again. 2nd group was 5 good shots with good follow through getting me a .353" CTC group. 3rd group was much the same as the first of this group of 3. I'm working on getting a log book as my memory of all the shots i've taken is getting a little crowded so to say. I mostly pay attention to cold bore placement, zeros between different loads, temperature changes and how they affect zero, those types of data. My lesson learned today is not to shrug off the dry fire practice the evening before range day just because it's getting a little late.

After today I believe I have a completed "do-all" load. Now I can start to obtain my averages so that I can understand what the norm is and be able to identify a problem when/if it comes up. It is comforting knowing that the possibility of a "bad day" isn't necessarily me, however I have the ability now to identify whether a bad day was just a normal day in the variation of the performance of the rifle and not me just sucking, or if there is a serious problem with the rifle that needs to be addressed, or perhaps it really was just me sucking.

Branden
 
#67
Re: What is a half MOA rifle?

yes. The author hides a lot of math. The math behind everything is simple statistics: a computer simulation based on even chances of direction throughout 360 degrees and distance based on standard deviation and a normal distribution. I think it would be +/- 18% 95% of the time for the average of 10 groups of 3. (I didn't run a simulation, so this is an approximation)

However, I find the idea of 3, 5, or 10 shot groups based on distance between farthest points of little importance outside bench shooting.

There will be differences depending on the shooter's fatigue level, accuracy of scope adjustment for dead center, etc., so I would try a much simpler approximation for useful information: shoot a bench target (the one that one can aim for the bottom corner of a black square) with your scope set for a few mils off in elevation and windage (so you don't shoot out the aiming point). Fire 20 rounds. Take the smallest circle that encompases 19 of those shots. The radius of that circle will be the distance from the bullseye that 95% of your shots will be.

I think that is accurate enough. If you shot 1000 rounds, you would get a slightly better approximation, but your MOA accuracy will decline with further distance shots (related to wind, etc.), so a rough approximation is good enough.

Back to that circle radius: 95% is roughly 1.65 standard deviations, so if you want 98% guarantee, you need around 2.05 standard deviations. So take your radius and multiple it by 2.05/1.65 or about 1.25 and that will be the radius 98% of the time your shots will be within that distance from your crosshairs.
 
#68
Re: What is a half MOA rifle?

GoughIsland, I like that technique, although you are making a big assumption that the SD of your 20-shot sample reflects the SD of the population. It will still underestimate it by a bit... but I like the simplicity.

What I like to do is a 5 X 5 and forget the extreme shot-to-shot distance, use On Target to calculate Average-to-Center, a much better metric that the extreme shot-to-shot (which is great for simplicity, but there are better tools available today).

There are target analysis tools that are better than On Target, but I like On Target for its bullet hole input mechanism. I wish that On Target could display horizontal and vertical shot distributions and show shots on a Cartesian as well as a polar coordinate system so I could do the analysis myself using JMP or some similar program.

This is all over the top for figuring out how accurate your gun is, but for load analysis, this type of statistical analysis is pretty critical.
 
#69
Re: What is a half MOA rifle?

Mr. Mayfield: you are right that the calculated SD will be slightly smaller than the real SD as it will be calculated from the center of the 20 shot group, which will be slightly off from the real center (of thousands of rounds). But it should be close enough, since other factors like angular accuracy at different distances, accuracy of centering the crosshairs on a sampled set of rounds at 100 yards, different accuracies with mirage, etc. will far outweigh these errors. The problem with statistics is that to get much more accuracy, you will have to shoot a logarithmic increase in rounds, and that gets both expensive and wears out your barrel. By that time, your personal accuracy may have changed with all that range time. For me, good enough is good enough.

Before I took one of my son's hunting, I made sure he knew how far away he could shoot a paper plate offhand. That was the distance I told him he could take the shot with me around. In military sniping, one might take a shot with a 30-40% likelihood of success if it didn't blow your cover and was an important target. In LE, I would assume one would generally not take the shot unless the success rate was a lot higher (but I am not in LE, so I'm guessing).
 
#70
Re: What is a half MOA rifle?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: sobrbiker883</div><div class="ubbcode-body">Its been my experience that 1/2 moa shooters are probably rarer than 1/2moa rifles....... </div></div>

I think a lot of it has to do with conditions as well, not everybody has/wants a benchrest rifle. I target shoot the same way I'm going to hunt with the same rifle.
smile.gif
 
#71
Re: What is a half MOA rifle?

GI, what I like about your approach is that it is more valid and easy to measure.

I like going to distance-to-center because, while it is less easy to measure, it throws away a lot less data. You can use every single piece of data and throw it on a cross-plot and see if your data is normal or not. If it isn't, you have fliers. And... technically, you should take the log of the distance-to-centers. Otherwise, the data will truly not be normal and things like SD will have less meaning.

Anyway, I am always interested in hearing new approaches.
 
#72
Re: What is a half MOA rifle?

I'm not sure how best to deal with fliers. The article referenced on SH above discusses fake fliers - just related to the distribution from normal variability. But you are right, that a real flier needs to be thrown out. The statistical tests I know to deal with such things are 5% trimmed mean or use of medians. I'm not as scientific as you (don't have that chemical engineering degree), so I pretend fliers are just part of the real variability in shooting (you and your rifle and the particulars of the day). I don't throw them out, and that leaves a big assumtion (maybe not true) that shots are normally distributed.
 
#73
Re: What is a half MOA rifle?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:</div><div class="ubbcode-body">...that leaves a big assumtion (maybe not true) that shots are normally distributed.</div></div>

I've wondered about that myself. It would take a lot more testing than I have the budget for to establish whether that's really the case.
 
#75
Re: What is a half MOA rifle?

Some phenomena with variations are not normally distributed. I could make some guesses about that, but they'd be...guesses. As an engineer, I'd like to <span style="font-style: italic">know</span> - but not enough to attempt to find out. I wish someone else would, though...
laugh.gif
 
#76
Re: What is a half MOA rifle?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: cavemanmoore</div><div class="ubbcode-body">If someone says they have a half MOA Rifle, does that mean all their groups are sub .500" at 100 yards, when using the correct ammo? Or does that mean the rifle shoots 1/2 MOA on a good day?

-Chris</div></div>

MOA is what it is, a unit of measurment; and, seems to me, since most rifles today, if they're not broken, will always shoot a bullet in the direction the barrel is pointed, the question is not what a .5 MOA rifle is as much as it's what a .5 MOA shooter is.
 
#77
Re: What is a half MOA rifle?

Fortunately, even if one does not have a normal distribution, statistical tests using the assumption of normality usually work. Most assumptions in statistics are not technically true (like absolute equality of variances in t-tests etc.) but they work. From my perspective, the reason a circle encompasing 19/20 shots works is that it really represents two different direction roughly normal distributions where the assumption is that the elevation distribution and the windage distribution are roughly the same.

Sterling: your comments are correct. In the end the variability represents a chain which includes the rifle, shooter (with all the variabilities involved in life), scope, and conditions at the time of firing.
 
#78
Re: What is a half MOA rifle?

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lindy</div><div class="ubbcode-body">As an engineer, I'd like to <span style="font-style: italic">know</span> - but not enough to attempt to find out. I wish someone else would, though...
laugh.gif

</div></div>

Here, here. I am happy to read the paper, not so happy to do the legwork. Everyone is a critic
wink.gif


If you take the log of these numbers, you should end up with a normal or close-to-normal distribution. You already know that it is non-normal because you can't have negative numbers and all fliers result in larger groups, not smaller ones.

Another important factor here is that I would suspect distribution is different for the windage axis versus the altitude axis. I would expect a true group of many shots to be oval shaped with more variation on the windage axis. So really, you need two distributions.

That is not to say that to determine accuracy, it is wrong to figure that the distribution is circular, but for instance, in selecting ammo / developing a load, I tend to focus more on the y-axis than the x-axis, which will be much more influenced by wind.

All of this is theoretical, but when it comes to load development, or for a gunsmith, determining whether to employ a different practice, it does get applied. We all need to use the same language, though. For that reason, back to the thread topic, when someone asks me what a gun shoots, I tell them the average of all 5-shot groups the gun has ever shot, minus load development / ammo selection shots, sighters, or any other types of testing done. If I change practice that results in a change of group size, then I use the new long-run average of 5-shot groups.
 
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