Can any good shooter wring full precision from guns?

[Toby Bradshaw]

Interesting, I'll run the windage sensitivities tomorrow.

You will find that failing to account for even 1-2mph wind is enough to make groups uncompetitive, especially at 200.

Are these statements as applicable for the 100-200yard range? Obviously I'm unfamiliar with the sport, but I do recall reading once that at least some top benchrest shooters wait for calm/stable conditions and then try to get off the full string as fast as possible, and that 1 shot per second is not an unusual rate of fire.

Many top shooters are machine-gunners, but even then they are often holding into a changing condition and using each shot as a sighter for the next while reading the flags. A real "runner" can get off 5 shots in about 10sec.

If conditions are still a factor at short range is the dispersion of groups predominantly along the horizontal axis?

Horizontal stringing ("weather report") is common among less experienced/talented shooters, but most competitive groups are round. Some top shooters will deliberately add a little bit of vertical to their tune if that makes the load less wind-sensitive.

(I assume stdev of muzzle velocities is near or in single digits, and there are no other primary factors contributing to vertical spread.)

Muzzle velocity variation matters very little at 100-200, as you will see if you plug the numbers into a ballistics program. I've never met anybody who measures it or cares about it in point-blank BR.

It's important to remember that a very small differences in an agg can move you many places in the standings of a big BR shoot. A few thousandths of an inch often separate first place from tenth. To win at a big shoot you need a good barrel, good bullets, great tune, great technique, and great condition reading skills.

 

[CatShooter]

What are typical muzzle velocities for these matches? With that we could estimate how much wind could impact results at these short ranges.

Interesting, I'll run the windage sensitivities tomorrow.

Without knowing the BCs of the individual bullets, you cannot run the wind sensitivitiess.

With gun #1 shooting at 3300 and gun #2 at 3400... you will not necessarily have the predicted sensitivities unless the BCs of the bullets are the same.

If #1 has a higher BC, it can drift less than gun #2, even though gun #2 is faster.

 

[David Bookstaber]

True, but that's a second-order concern given that everyone's shooting bullets roughly the same shape. And I assumed roughly the same calibers and weights (and therefore similar sectional densities), although maybe that's also an incorrect assumption?

In any case, TobyBradshaw was right: with groups this small even failing to account for 1mph of crosswind will have a measurable effect -- on the order of .1MOA per 1mph. So unless we can confirm negligible winds during the event even at these short ranges we're compounding shooter wind-reading skill with pure bench skill.

If I could rephrase my original question it would be: Does an average "competent" shooter introduce significant dispersion into his groups (i.e., relative to the dispersion inherent in a good sporting rifle with match ammo, so say "significant" is adding more than .1-.2MOA vs the same gun in a machine rest)? The closest answer I've found could be provided by people familiar with the activity at the Houston Warehouse, where there was no wind and lots of different shooters and guns came through.

The NBRSA data sort of put a lower bound on the answer: The best shooters appear to be able to shoot within the margin of error of the same shooters on rail guns. But it's answering a different question since the primary source of dispersion at that level in that sport is wind. Not to mention a premium bench rest and rifle are easier to shoot without disturbing than any other rifle and rests an average rifleman would have at his disposal.

 

[FergusBailey]

I don't think you are seeing the true benefit a rail has over a bag gun from your analysis. The difference between 5 shot groups and 10 shot groups is significant - for example a 5 shot "screamer" at 100 is anything under .100, and under .200 at 200 yards. With 10 shot groups, a screamer is sub .200 and sub .450 respectively (note this is as per the Australian rule book, but from memory the US awards are the same).

To more accurately undertake your analysis, you need to find matches where 5 shot unlimited is held, along with the bag gun classes. While these are not held at a nationals, they are held in some regional areas, Visalia CA and the south east region come to mind. I THINK I have results from some of these matches, but will have to go looking for them.

You will see a lot of advantage goes to a rail over a bag gun in a like-for-like comparison (yes, there are exceptions such as http://bulletin.accurateshooter.com/2011/06/0-022-group-possible-new-unlimited-100-yard-nbrsa-record/ but remember this is a group, not an agg record).

 

[David Bookstaber]

The statistics showing extreme spread on 10-shot groups should be 1.24x 5-shot groups assume the shot dispersion is roughly symmetric.

If wind reading and compensation are the primary sources of dispersion then we might say a horizontal dispersion model would be more accurate, but in that case 10-shot groups are still only 1.32x bigger than 5-shot groups.

A key assumption of these statistical models is that each shot is identically handicapped (i.e., drawn from the same distribution). For what you say to be true longer shot strings have to be disproportionately handicapped. If that is the reality it would be great to figure out why. Here are some plausible sources of such a handicap:

[list type=decimal]
[*]Conditions affecting point of impact change more over the time it takes to fire 10 shots than 5, and shooters' abilities to compensate for those condition changes is limited (or non-existent).
[*]Shooters physiologically can't maintain the same level of performance for 10 shots as they do for 5.
[*]Something happens to these guns over longer strings that increases their dispersion -- e.g., maybe they have to be cleaned every 5 shots to avoid losing accuracy, or maybe even these massive BR barrels suffer from heat distortion.
[/list]

 

[M14AMU]

What's the point??

 

[Toby Bradshaw]

A key assumption of these statistical models is that each shot is identically handicapped (i.e., drawn from the same distribution). For what you say to be true longer shot strings have to be disproportionately handicapped. If that is the reality it would be great to figure out why. Here are some plausible sources of such a handicap:

[list type=decimal]
[*]Conditions affecting point of impact change more over the time it takes to fire 10 shots than 5. [/list]

This is the reason.

A shortcut to answer your original question would be to ask the top guns whether they would shoot a rail gun or a bag gun if there were no restrictions. We can see from the "unlimited" class entries (overwhelmingly dominated by rail guns) which one they would choose.

You can bet that those at the top of the HOF rankings have produced a mountain of lead in testing under real-world conditions to reach their conclusions.

As the old canard goes, "In theory, theory and practice are the same. In practice, they're not."

 

[David Bookstaber]

That's compelling enough. Now, especially in light of the previous observation/question, do you happen to know why they choose rail guns when they can? Is it because having to nudge a heavy bag gun back into place introduces enough error that you have to sight each shot, whereas with a rail gun you can just sit back and watch the wind flags? Is there anything else that makes rail guns intrinsically more precise, or are they just easier to shoot?

And are you sure it's not just because anyone who owns one is going to bring it out to play every chance they get? This is actually a serious question, because you did note before that occasionally someone shooting a bag gun in unlimited will beat all the rail guns, but that it's not common. The simplest conclusion from these observations are that rail guns are intrinsically more precise.

But I wonder if there is evidence to reject this alternative hypothesis: You can't be competitive in BR if you have financial constraints. Skill alone can't make up for not having the best equipment. The guys shooting the bag guns in unlimited presumably couldn't afford to buy and load for a rail gun, so the fact that they aren't shooting one suggests a high probability they have financial constraints that may be hampering their bag gun as well.

Or are there top competitive heavy bag shooters who just haven't gotten into rail guns, but who do have every resource at their disposal, and who shoot their bag guns in unlimited and can't consistently place with the rail guns?

 

[Toby Bradshaw]

A human isn't as consistent as a return-to-battery machine. It's about that simple. And when the winning margins are measure in thousandths of an inch, consistency is everything.

To some extent the competitive BR game is also a money game. Not every barrel is great, or even good. Top shooters are willing to buy and test quite a few barrels to find one that's competitive. It's a similar story for bullets (jackets, really). But anyone who is OFTEN at the top of the BR standings did it with hard work and lots of practice and plenty of native ability, not just with money.

Given the cost of components over several seasons of competition, the price of rail gun isn't scaring away a serious competitor. So it's safe to assume that no human being can CONSISTENTLY outshoot a rail at the highest levels of the sport.

 

[David Bookstaber]

Thanks again for the great info and explanations!