Posted: 5/5/2017 9:56:04 AM EDT
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What range do you usually test different rounds at before deciding that's the best round for your set up? I was sighting in my 6.5 creedmoor the other day at 100. I shot both the 140 and 147 grain ELD-M rounds. The 140 seemed to be the best here but it could have been me.
The guy at my LGS said to go at least to 300 before deciding. He told me that at 100 the round might not be fully stabilized yet and the 147 might be better at 300. He kept saying the bullet needs time to go to sleep. Is that true or was he blowing smoke? I know him and know he shoots distance quite a bit but I haven't heard this before. |
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Quoted:
Bullets do not "settle" at longer ranges. Your 300 yard groups will always be bigger than your 100 yard groups. That being said, your should test at the ranges where you'll be doing most of your shooting. I'm still new to this game and have a lot to learn. At our cabin we can shoot to over 800 so I'm working on getting there with the intent to go past that when I'm good enough. I was just wondering where guys do most of their testing/development. |
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100 yard testing will tend to minimize the atmospheric variables, however you need to either verify that with longer range comparative testing or also test velocity.
In essence, you may have two loads that shoot equal good consecutive 5 shot groups, but one may have a standard deviation in velocity of 12 fps while the other has a standard deviation in velocity of 36 fps. The difference is, for example, with an average velocity of 3000 fps and an SD of 12 fps: 1) 68 out of 100 rounds fired will have velocities between 2988 fps and 3012 fps; 2) 13 out of 100 will have a velocity between 2976 fps and 2988 fps; 3) 13 out of 100 will have a velocity between 3012 fps and 3024 fps; 4) 3 out of 100 will have a velocity between 2964 fps and 2976 fps; and 5) 3 out of 100 will have a velocity between 3024 fps and 3036 fps. In other words, 68% of the rounds fired will have an extreme spread of just 24 fps, 27% of the rounds fired will have an extreme spread of 48 fps, with the 3rd standard deviation outliers having and extreme spread of 72 fps. However if you triple that SD to 36, you also triple the extreme spread to 68% of the rounds having an extreme spread of 72 fps, 27% will have an extreme spread of 144 fps and the 3rd standard deviation outliers will have an extreme spread of 216 fps. Those larger SDs and extreme spreads will increase both horizontal and vertical dispersion at longer range. Consequently, if you've got two loads that are equally accurate at 100 yards, the load with the lowest SD will almost always be more accurate at long range. And, if you can't confirm this at a 600-1000 yard range, your best bet when accuracy is otherwise equal is to always take the load with the lower SD. ---- The other caution with ammo testing is to use a large enough sample. Even a bad load can occasionally post an abnormally good group. Accuracy also has a normal distribution curve like velocity, so you have to shoot enough groups to ensure you didn't get 1 or 2 groups that just happen to fall on in the right hand tail of the distribution by random chance. If you're testing accuracy and velocity together, a half dozen 5 shot groups will start to give you a good basis for both group analysis and a sufficiently high number of data points for a reliable SD in velocity. Rifles also vary in terms of how much variation there is in group size - one of the things that leads people to regard some rifles as more accurate than others. I have a pair of otherwise identical rifles that have similar average group sizes, but posts 5 shot groups that vary from one half MOA to 1.5 MOA, while the other one very consistently holds 1 MOA, even sequential 10 shot groups. The former will post better groups from time to time, while the latter is much more consistent. |
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Quoted:
100 yard testing will tend to minimize the atmospheric variables, however you need to either verify that with longer range comparative testing or also test velocity. In essence, you may have two loads that shoot equal good consecutive 5 shot groups, but one may have a standard deviation in velocity of 12 fps while the other has a standard deviation in velocity of 36 fps. The difference is, for example, with an average velocity of 3000 fps and an SD of 12 fps: 1) 68 out of 100 rounds fired will have velocities between 2988 fps and 3012 fps; 2) 13 out of 100 will have a velocity between 2976 fps and 2988 fps; 3) 13 out of 100 will have a velocity between 3012 fps and 3024 fps; 4) 3 out of 100 will have a velocity between 2964 fps and 2976 fps; and 5) 3 out of 100 will have a velocity between 3024 fps and 3036 fps. In other words, 68% of the rounds fired will have an extreme spread of just 24 fps, 27% of the rounds fired will have an extreme spread of 48 fps, with the 3rd standard deviation outliers having and extreme spread of 72 fps. However if you triple that SD to 36, you also triple the extreme spread to 68% of the rounds having an extreme spread of 72 fps, 27% will have an extreme spread of 144 fps and the 3rd standard deviation outliers will have an extreme spread of 216 fps. Those larger SDs and extreme spreads will increase both horizontal and vertical dispersion at longer range. Consequently, if you've got two loads that are equally accurate at 100 yards, the load with the lowest SD will almost always be more accurate at long range. And, if you can't confirm this at a 600-1000 yard range, your best bet when accuracy is otherwise equal is to always take the load with the lower SD. ---- The other caution with ammo testing is to use a large enough sample. Even a bad load can occasionally post an abnormally good group. Accuracy also has a normal distribution curve like velocity, so you have to shoot enough groups to ensure you didn't get 1 or 2 groups that just happen to fall on in the right hand tail of the distribution by random chance. If you're testing accuracy and velocity together, a half dozen 5 shot groups will start to give you a good basis for both group analysis and a sufficiently high number of data points for a reliable SD in velocity. Rifles also vary in terms of how much variation there is in group size - one of the things that leads people to regard some rifles as more accurate than others. I have a pair of otherwise identical rifles that have similar average group sizes, but posts 5 shot groups that vary from one half MOA to 1.5 MOA, while the other one very consistently holds 1 MOA, even sequential 10 shot groups. The former will post better groups from time to time, while the latter is much more consistent. |