Intuitively if you shoot only one series, the result will be highly susceptible to random deviations. If we shoot not one series, but two and more the result the influence of randomness will be less, we will become a little closer to the Truth. With each new series, the Truth becomes closer, but you can go to the Truth infinitely and you still run into the infinitely small and you run out of cartridges.
The criteria for "sufficient" closeness to the Truth - the universal URURA scale are bellow.
(ATTENTION: the figures in the table correspond to half the confidence interval, ie, for example, 37.3% means +- 37.3%. Colors and calculations correspond to URURA.)
| shots | number of series | |||||||||||
| in series | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 | 11 | 12 |
| 3 | 72.6% | 51.3% | 41.9% | 36.3% | 32.4% | 29.6% | 27.4% | 25.7% | 24.2% | 22.9% | 21.9% | 20.9% |
| 4 | 60.1% | 42.5% | 34.7% | 30.1% | 26.9% | 24.5% | 22.7% | 21.3% | 20.0% | 19.0% | 18.1% | 17.4% |
| 5 | 52.8% | 37.3% | 30.5% | 26.4% | 23.6% | 21.6% | 20.0% | 18.7% | 17.6% | 16.7% | 15.9% | 15.2% |
| 6 | 48.1% | 34.0% | 27.8% | 24.0% | 21.5% | 19.6% | 18.2% | 17.0% | 16.0% | 15.2% | 14.5% | 13.9% |
| 7 | 44.6% | 31.5% | 25.8% | 22.3% | 20.0% | 18.2% | 16.9% | 15.8% | 14.9% | 14.1% | 13.5% | 12.9% |
| 8 | 42.0% | 29.7% | 24.2% | 21.0% | 18.8% | 17.1% | 15.9% | 14.8% | 14.0% | 13.3% | 12.7% | 12.1% |
| 9 | 39.9% | 28.2% | 23.0% | 19.9% | 17.8% | 16.3% | 15.1% | 14.1% | 13.3% | 12.6% | 12.0% | 11.5% |
| 10 | 38.1% | 27.0% | 22.0% | 19.1% | 17.0% | 15.6% | 14.4% | 13.5% | 12.7% | 12.1% | 11.5% | 11.0% |
| 11 | 36.7% | 25.9% | 21.2% | 18.3% | 16.4% | 15.0% | 13.9% | 13.0% | 12.2% | 11.6% | 11.1% | 10.6% |
| 12 | 35.4% | 25.0% | 20.4% | 17.7% | 15.8% | 14.5% | 13.4% | 12.5% | 11.8% | 11.2% | 10.7% | 10.2% |
| 13 | 34.4% | 24.3% | 19.8% | 17.2% | 15.4% | 14.0% | 13.0% | 12.2% | 11.5% | 10.9% | 10.4% | 9.9% |
| 14 | 33.4% | 23.6% | 19.3% | 16.7% | 14.9% | 13.6% | 12.6% | 11.8% | 11.1% | 10.6% | 10.1% | 9.6% |
| 15 | 32.6% | 23.0% | 18.8% | 16.3% | 14.6% | 13.3% | 12.3% | 11.5% | 10.9% | 10.3% | 9.8% | 9.4% |
| 16 | 31.9% | 22.5% | 18.4% | 15.9% | 14.2% | 13.0% | 12.0% | 11.3% | 10.6% | 10.1% | 9.6% | 9.2% |
| 17 | 31.2% | 22.0% | 18.0% | 15.6% | 13.9% | 12.7% | 11.8% | 11.0% | 10.4% | 9.9% | 9.4% | 9.0% |
| 18 | 30.5% | 21.6% | 17.6% | 15.3% | 13.6% | 12.5% | 11.5% | 10.8% | 10.2% | 9.7% | 9.2% | 8.8% |
| 19 | 30.0% | 21.2% | 17.3% | 15.0% | 13.4% | 12.2% | 11.3% | 10.6% | 10.0% | 9.5% | 9.0% | 8.7% |
| 20 | 29.5% | 20.8% | 17.0% | 14.7% | 13.2% | 12.0% | 11.1% | 10.4% | 9.8% | 9.3% | 8.9% | 8.5% |
In other words, the next time a sniper (or worse, a rifle manufacturer) posts a picture with a "group" of 3 holes, you will know that the truth is likely to lie somewhere within +- 72.6% of the declared value (not to mention the fact that for the D95 the resulting insanity needs to be doubled).
The average of two series of 5 shots, which is so worried about the Russian-speaking rifleman, goes with a confidence interval of +- 37.3%. In other words, for example: two series flew on average per minute with a high probability the truth is in the range of 0.627 - 1.373 MOA (and D95, respectively, in the range of 1 - 2.2 MOA).
Before declaring "my rifle is capable of ...", I now meditate on this tablet for a long time.
Dear reader, you have one more table which says how many series you need to shoot to reach each level of URURA.
| Confidence interval, +-% | ||||||||
| shots | 25% | 20% | 15% | 10% | ||||
| in series | series | shots | series | shots | series | shots | series | shots |
| 2 | 16.8 | 34 | 26.2 | 54 | 46.6 | 94 | 104.9 | 210 |
| 3 | 8.4 | 27 | 13.2 | 42 | 23.4 | 72 | 52.6 | 159 |
| 4 | 5.8 | 24 | 9.0 | 40 | 16.1 | 68 | 36.1 | 148 |
| 5 | 4.5 | 25 | 7.0 | 35 | 12.4 | 65 | 27.9 | 140 |
| 6 | 3.7 | 24 | 5.8 | 36 | 10.3 | 66 | 23.1 | 144 |
| 7 | 3.2 | 28 | 5.0 | 35 | 8.8 | 63 | 19.9 | 140 |
| 8 | 2.8 | 24 | 4.4 | 40 | 7.8 | 64 | 17.6 | 144 |
| 9 | 2.5 | 27 | 4.0 | 36 | 7.1 | 72 | 15.9 | 144 |
| 10 | 2.3 | 30 | 3.6 | 40 | 6.5 | 70 | 14.5 | 150 |
| 11 | 2.1 | 33 | 3.4 | 44 | 6.0 | 66 | 13.4 | 154 |
| 12 | 2.0 | 36 | 3.1 | 48 | 5.6 | 72 | 12.5 | 156 |
| 13 | 1.9 | 26 | 3.0 | 39 | 5.3 | 78 | 11.8 | 156 |
| 14 | 1.8 | 28 | 2.8 | 42 | 5.0 | 70 | 11.2 | 168 |
| 15 | 1.7 | 30 | 2.7 | 45 | 4.7 | 75 | 10.6 | 165 |
| 16 | 1.6 | 32 | 2.5 | 48 | 4.5 | 80 | 10.2 | 176 |
| 17 | 1.6 | 34 | 2.4 | 51 | 4.3 | 85 | 9.7 | 170 |
| 18 | 1.5 | 36 | 2.3 | 54 | 4.1 | 90 | 9.3 | 180 |
| 19 | 1.4 | 38 | 2.2 | 57 | 4.0 | 76 | 9.0 | 171 |
| 20 | 1.4 | 40 | 2.2 | 60 | 3.9 | 80 | 8.7 | 180 |
The most effective series (in terms of the consumption of cartridges for information content) are 5, 6 and 7 shots. Even with "effective" series of 5 to achieve URURA.3 you will need no less than 65 rounds - 13 series. To add up the minimum idea of the spread, you need already 5 series (the so-called "NRA method").
Do not lose your vigilance!
Meet:universal scale URURA = "Confidence Level in Scatter".
The level of trust is set by the generally accepted 95%.
The URURA itself is determined by the confidence interval (CI) around the obtained value of the spread as a percentage of its value. The estimate does not depend on the units of measurement or on the actual value of the spread.
For example if there is an experimentally obtained scatter of 1.1 MOA with a confidence interval of 0.81 .. 1.33 MOA, the total interval in percent = (1.1-0.81) /1.1 + (1.33 - 1.1) /1.1 = (1.33-0.81) / 1.1 = 0.4727272. . = 47.3%
Threshold values were determined based on common sense and the number of rounds that the average amateur shooter is willing to spend on shooting for accuracy.
| URURA.0 | CI > 50% : Completely untenable claim to "estimate", the confidence interval is more than half of the quantity itself. A typical case of a senseless waste of cartridges (the background color seems to hint). |
| URURA.1 | 50% >= CI > 40% : Red level. It is not suitable for most practical applications, it gives "approximate direction towards the pole". |
| URURA.2 | 40% >= CI > 30% : Orange level. Perhaps the lower limit, giving an idea of the real spread of the rifle. |
| URURA.3 | 30% >= CI > 20% : Yellow level. The score is "chorus". It can be used for modeling, calculations, estimating the probability of hitting a certain target, etc. 25% and below - Level 3+, confidence sufficient for most practical applications. |
| URURA.4 | 20% >= CI : Green level. Excellent rating. Enough, it's time to stop, cartridges are not free, barrels are not eternal. |
| URURA.5 (IDKFA) | 10% >= CI : Ahh! Dude, pour the cartridges! URURA5 characterizes not so much the barrel / cartridge as the owner. If an amateur shooter is able to plant about 400 rounds (then measure the coordinates of each hole, and then drive them into the computer) just to assess the spread of the rifle, take off my hat, bow my tusks - this is a maniac and a bore, a champion out of categories! I didn't even think of colors for the level. |
URURA.1 requires approximately 16 rounds, URURA.2 - 24 rounds, URURA.3 - 45 rounds, URURA.3 + - 65 cartridges, URURA.4 - about a hundred, URURA.5 - about 400.
source: https://geladen.livejournal.com/50902.html
source: https://geladen.livejournal.com/50456.html