I was thinking that if the donut gets too fat the bullet will get pinched when the round is chambered. The pinch will cause pressure spikes and big ES.
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ES too high
- Thread starter markl323
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I was thinking that if the donut gets too fat the bullet will get pinched when the round is chambered. The pinch will cause pressure spikes and big ES.
Yeah, whether it's the donut or the carbon ring causing a pinch, it will cause pressure spikes. But, unless the round is seated long enough for the bullet to make contact with the lands, I don't know why chambering would cause the bullet to move into the donut . . . ??? I suppose if the neck tension wasn't sufficient, recoil might move the bullet to touch the donut to some extent, but then, that would mean there more than just the donut at play that would cause such an ES.
yes. I have been going through the mandrel step very slowly! same with shoulder bumping and bullet seating.
I have tried the followings and have not been to get rid of groups with high ES:
H4350
Alpha SRP + CCI 400
RL 16
Alpha SRP with CCI 450 ad BR4
Lapua LRP with CCI 250
I'm going to try a new primer Federal 205Match next trip to the range. Plus I'll do an OCW test as well. Plus I have the Annie annealer coming LOL. I'm so committed now.
Something always keep in mind is exactly how SD and ES work statistically. Most aren't aware what the actual SD numbers their chrono spits out actually mean.
To get the correct data, you'll need to extrapolate the SD using confidence intervals and the amount of shots fired. 95% is the most common interval used.
So, for example, if you fire a 10 shot string, and have an SD of 8......using a 95% confidence interval, your true SD is somewhere between 5.5 and 14.5fps. Meaning if you were to shoot enough rounds to be very sure your SD is the true SD of the ammo, it would be somewhere between those two, 95% of the time.
Now, SD itself is a distribution. Meaning 68% of your shots will be within one standard deviation. If you have an 8sd, 68% of your shots will have an ES of 16 (8 each way).
95% of your shots will be within two standard deviations. Which means if you shot 100 rounds, 95 of them would be inside an ES of 32fps (two SD of 8 each way.
99.7% of your shots will be within three standard deviations. We'll just round up to 100%.
Which means, if you have a true sd of 8, if you shoot 100 shots, you will have an extreme spread of 48fps.
If you only shoot a 10 shot group and get an SD of 8, with the confidence interval calculated, you could actually have an ES of up to 87fps.
To get the correct data, you'll need to extrapolate the SD using confidence intervals and the amount of shots fired. 95% is the most common interval used.
So, for example, if you fire a 10 shot string, and have an SD of 8......using a 95% confidence interval, your true SD is somewhere between 5.5 and 14.5fps. Meaning if you were to shoot enough rounds to be very sure your SD is the true SD of the ammo, it would be somewhere between those two, 95% of the time.
Now, SD itself is a distribution. Meaning 68% of your shots will be within one standard deviation. If you have an 8sd, 68% of your shots will have an ES of 16 (8 each way).
95% of your shots will be within two standard deviations. Which means if you shot 100 rounds, 95 of them would be inside an ES of 32fps (two SD of 8 each way.
99.7% of your shots will be within three standard deviations. We'll just round up to 100%.
Which means, if you have a true sd of 8, if you shoot 100 shots, you will have an extreme spread of 48fps.
If you only shoot a 10 shot group and get an SD of 8, with the confidence interval calculated, you could actually have an ES of up to 87fps.
If you have a true to life SD of 5, your ES is 30.
That should put a lot of this in perspective.
Most people would agree a true to life real 5fps SD is extremely good ammo. Some of the best ammo you could ever make.
And that ammo will still have an ES of 30fps.
That should put a lot of this in perspective.
Most people would agree a true to life real 5fps SD is extremely good ammo. Some of the best ammo you could ever make.
And that ammo will still have an ES of 30fps.
I always looked at ES/SD like, "Big numbers no good, small numbers better, and single digit best".
SD really gives you all the info you need. Anytime you have an ES smaller of around 6 times your SD, all that means is that you haven't shot enough shots to get your real ES.
And ya, the smaller your SD, the better. Even when shooting very small sample sizes, the smaller your observed SD, the smaller the range of a 95% confidence will be.
For example, 10 shot strings
5sd = 3fps - 9fps
8sd = 5.5fps - 14.5fps
If your 10 shot string has a 5sd, you should not be worried if your ES is 54fps or less.
Meaning, if you take two different loads, shoot 10 of them across your chrono, both have a 5sd, but one has a 50es and the other has a 30es.....
You literally cannot say the 30es ammo is better as they are both inside the 95% confidence interval.
Not understanding this is a very big reason people chase their tale with ammo and chrono.
FYI, if your SD is 10......here is how your ES might play out. Based on 5 or 10 shot strings:
If you shoot a 5 shot string and get an SD of 10, your ES could be as high as 168fps
If you shoot a 10 shot string and get an SD of 10, your ES could be as high as 108fps
If your ammo is actually a true to life 10sd, your ES is 60. Just the way it works. So, being over 30 ES with a 10sd is extremely normal.
When you shoot a string and get an SD of 10, but your ES is 20......that 20es is not a valid observation. It is the product of not enough shots to make a proper observation of your ES, which is around 60(if your ammo is a true 10sd).
If people don't take into consideration the ammo temp vs ambient temp, that will have them chasing tails too! Like, ammo stored in air conditioned house then hit the range in hotter temps. I'm letting my ammo acclimate for an hour before shooting. Tells a lot about powder temperature sensitivity!
Holy shit! Great job!
I have a 708 120gr Hammer load 50 shots with 9SD and thought I deserved a medal!
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Anyone have a good load for 115 DTACS with Alpha brass and H4350?
I am getting 2850 with 109 Bergers and 36.1g H4350.
I am getting 2850 with 109 Bergers and 36.1g H4350.
Hi all,
I need to give an update on this! Everyone has been very helpful.
Shortly making this thread, I had to take a break from shooting. When I got back to this hobby, i had to switch to a new rifle a factory 300 PRC.
Taking what i have learned from this thread and some help from a member at this site, I have made some major changes. Initially my average SD for the 300 PRC was about 15. But I have since reduced it down to about 7.7. Things that I noticed and fixed:
- The Lyman press was not good it frequently caused brass to get stuck. I think concentricity issue. I now use two Rock Chuckers. One for FLS and depriming and one for the mandrel.
- I now try 3 different powders and 3 different brands of primers. I think this gives the biggest improvements for me.
- I also annneal, full length size, trim cases, sort primers by weight, chamfer, deburr case mouths.
- Instead of wet tumble with SS I use an ultrasonic cleaner.
- I seat primers 0.002” crush.
- I also upgraded all my equipments to 21st centuries, AccuracyOne and L.E. Wilson.
My next step is neck turning and see if I get even better ES/SD. This has been quite a ride
I need to give an update on this! Everyone has been very helpful.
Shortly making this thread, I had to take a break from shooting. When I got back to this hobby, i had to switch to a new rifle a factory 300 PRC.
Taking what i have learned from this thread and some help from a member at this site, I have made some major changes. Initially my average SD for the 300 PRC was about 15. But I have since reduced it down to about 7.7. Things that I noticed and fixed:
- The Lyman press was not good it frequently caused brass to get stuck. I think concentricity issue. I now use two Rock Chuckers. One for FLS and depriming and one for the mandrel.
- I now try 3 different powders and 3 different brands of primers. I think this gives the biggest improvements for me.
- I also annneal, full length size, trim cases, sort primers by weight, chamfer, deburr case mouths.
- Instead of wet tumble with SS I use an ultrasonic cleaner.
- I seat primers 0.002” crush.
- I also upgraded all my equipments to 21st centuries, AccuracyOne and L.E. Wilson.
My next step is neck turning and see if I get even better ES/SD. This has been quite a ride
Stand them up in a Tupperware container. Then it's easy to spray in the necks. I just lean my Tupperware against something at a 45 and start filling it like I would the hopper on my Giraud.
I wanted to comment on the behavior of sample ES at small sample sizes. It suffers the same consequence as sample SD. As can be seen below, sample ES can be underestimated much like sample SD when the sample size is small. Depending on the population SD, convergence onto the population value can be as small as 10 observations or as high as 30 observations. Since you do not know the population standard deviation, you have no idea how underestimated the statistic might be. Worse, the plots below show “on-average” results. No one is testing their rifle 500k times just to estimate a statistic. The minimums and maximums in the table illustrate how disperse any one test could be. As one would expect, more observations shrink the range between the minimum and maximum.
TLDR:
ES at small sample sizes are unreliable.
TLDR:
ES at small sample sizes are unreliable.
