just got off the range. i am having problems with es/sd. all loads shot through CED chrony. 18' douglas 1-7' ar-15 barrel. load info--winchester brass, case inside necks polished, sinclair mandrel ran through necks, outside necks cleaned up with forster neck turn, run through redding FL die, weighed 94.5 grns +or- .2, trimmed, chamfered, flash hole debur, primer pocket uniformed. 23.6 tac, wolf srm primer, sierra 77--comparator sorted. OAL apx 2.255. measured with hornady comparator, all within .002. my es avg. for 5 strings--71 fps. my sd for 5 strings is 22.44 fps. what is going on? do i need to switch to a FL bushing die and then run an expander mandrel through for more uniform neck tension? not sure what my tension is now,dont have my log by me), should i switch so i get a more uniform .003-.004 grip?
sd and es
- Thread starter cmillard
- Start date
First thing I would try, would be primers to try to shrink that ES. As far as SD it means nothing to me. I'm looking for the extreme spead.
Finding the accuracy node with your powder charge will help also. Once you hit that node your ES will shrink.
On my accuracy node in my Dasher my ES is any where from 28 on the high end to and 4 on the low end, on a 5 shot string.
Different lighting conditions will also affect chrono readings I use the IR screens on the CED M2, It helps in bright sunlight.
Finding the accuracy node with your powder charge will help also. Once you hit that node your ES will shrink.
On my accuracy node in my Dasher my ES is any where from 28 on the high end to and 4 on the low end, on a 5 shot string.
Different lighting conditions will also affect chrono readings I use the IR screens on the CED M2, It helps in bright sunlight.
If your ES exceeds three time your SD, you have unrecognized influences.
Cole, I'll offer a few thoughts, but my first one is that the .223 has been, in my experience, one of the toughest cartridges to get a low ES/SD out of. I could speculate why, but I don't have hard facts on that, it just seems to be that way. Now, on to some hopefully helpful ideas:
1. Personally, I find SD to be a more relevant measure of my loads. SD is a measure of the load's overall consistency whereas ES is a measure of the two worst shots. It's almost the same concept as group shooting,ES) vesus score shooting,SD). Suppose you fire a 20 shot string over the chrono and 19 of those shots have a velocity of 2850 and the 20th is 2900. You were doing a pretty darn good job of loading. The average vel. is 2852.5, but the ES is 50 and a lot of people would look at that and say it's a bad load. However, the SD was 11.2 and is indicative of a good load.
2. Now, suppose that your shots were half at 2875 and half at 2825. The average vel. is 2850 and the ES is 50, about the same as before, but the SD is now 25.6, more than double. Why? Because the load is much more irregular. SD is essentially a measure of how far from average you can expect a given shot to be,that's a fairly simplified description, but useful). SD considers all shots fired, not just the extremes.
3. A shot that is more than 3X SD from the average is a fluke which can and should be discounted when making calculations. They will just happen, even with perfect loads, that's part of the randomness that exists in any population. I would pick the 11.2 SD load every time in the above examples.
4. That's a nice discussion of statistics, but it doesn't get you to a better load, does it? Some loads are just not going to ES/SD well even when assembled perfectly. Powder type, burn rate and amount are big factors here - as are primers. I think you're using the best possible primer for a small rifle case, so I'd focus on the powder type and charge. Your combination isn't one I have shot, but RL15 might be a better choice as it tends to give good results in .223 with 69 and 80 gr. bullets. The 77's are kind of different because of their long bearing surface, though, so it's not a sure thing - but probably a good one to try. I suspect that the biggest part of your quest will be in powders.
5. One last tip from a lot of chronographing is that how consistently you hold the rifle affects the MV of the shot and thus all the statistical results. I can alter MV in a predictable fashion by holding loose or tight. Make sure that you are consistent in the grip and shoulder pressure when firing over a chrono.
6. Handy SD calculator: http://www.easycalculation.com/statistics/standard-deviation.php
1. Personally, I find SD to be a more relevant measure of my loads. SD is a measure of the load's overall consistency whereas ES is a measure of the two worst shots. It's almost the same concept as group shooting,ES) vesus score shooting,SD). Suppose you fire a 20 shot string over the chrono and 19 of those shots have a velocity of 2850 and the 20th is 2900. You were doing a pretty darn good job of loading. The average vel. is 2852.5, but the ES is 50 and a lot of people would look at that and say it's a bad load. However, the SD was 11.2 and is indicative of a good load.
2. Now, suppose that your shots were half at 2875 and half at 2825. The average vel. is 2850 and the ES is 50, about the same as before, but the SD is now 25.6, more than double. Why? Because the load is much more irregular. SD is essentially a measure of how far from average you can expect a given shot to be,that's a fairly simplified description, but useful). SD considers all shots fired, not just the extremes.
3. A shot that is more than 3X SD from the average is a fluke which can and should be discounted when making calculations. They will just happen, even with perfect loads, that's part of the randomness that exists in any population. I would pick the 11.2 SD load every time in the above examples.
4. That's a nice discussion of statistics, but it doesn't get you to a better load, does it? Some loads are just not going to ES/SD well even when assembled perfectly. Powder type, burn rate and amount are big factors here - as are primers. I think you're using the best possible primer for a small rifle case, so I'd focus on the powder type and charge. Your combination isn't one I have shot, but RL15 might be a better choice as it tends to give good results in .223 with 69 and 80 gr. bullets. The 77's are kind of different because of their long bearing surface, though, so it's not a sure thing - but probably a good one to try. I suspect that the biggest part of your quest will be in powders.
5. One last tip from a lot of chronographing is that how consistently you hold the rifle affects the MV of the shot and thus all the statistical results. I can alter MV in a predictable fashion by holding loose or tight. Make sure that you are consistent in the grip and shoulder pressure when firing over a chrono.
6. Handy SD calculator: http://www.easycalculation.com/statistics/standard-deviation.php
Like most every thing regarding shooting, everything is relative. In this case...ES vs SD...a lot of what is/is not important depends on what your game is and what distance you are shooting. Use your chrono to develop a load that meets YOUR standards for consistent and acceptable accuracy.
Having said that, I'll mention that while a 50 fps ES with its inherent 10' of vertical at 1000y would drive a Long Range shooter nuts, regardless of how good the SD is, it may not be even noticeable to a 100y Bench Rest shooter....who probably does not even find it necessary to weigh his powder charge in increments of 1 kernel like his long range shooting buddy.
Having said that, I'll mention that while a 50 fps ES with its inherent 10' of vertical at 1000y would drive a Long Range shooter nuts, regardless of how good the SD is, it may not be even noticeable to a 100y Bench Rest shooter....who probably does not even find it necessary to weigh his powder charge in increments of 1 kernel like his long range shooting buddy.
Like most every thing regarding shooting, everything is relative. In this case...ES vs SD...a lot of what is/is not important depends on what your game is and what distance you are shooting. Use your chrono to develop a load that meets YOUR standards for consistent and acceptable accuracy.
Having said that, I'll mention that while a 50 fps ES with its inherent 10' of vertical at 1000y would drive a Long Range shooter nuts, regardless of how good the SD is, it may not be even noticeable to a 100y Bench Rest shooter....who probably does not even find it necessary to weigh his powder charge in increments of 1 kernel like his long range shooting buddy.
I agree with this guy. I worked up a load at 100yds in my .308, and it was holding 3/8in groups. when I stepped it out to 500yds it went crazy. 4' to 5' groups. So when I chrono the next 5 rnds there was a ES 57.
I was using win brass. It was not a good lot of brass. So I went to lapua brass and uniformed everything with a lot less work and more time on the range. The same load in the lapua brass cut the ES down to 14. May not fix the problem but this is just what I have experienced with high ES.
Having said that, I'll mention that while a 50 fps ES with its inherent 10' of vertical at 1000y would drive a Long Range shooter nuts, regardless of how good the SD is, it may not be even noticeable to a 100y Bench Rest shooter....who probably does not even find it necessary to weigh his powder charge in increments of 1 kernel like his long range shooting buddy.
I agree with this guy. I worked up a load at 100yds in my .308, and it was holding 3/8in groups. when I stepped it out to 500yds it went crazy. 4' to 5' groups. So when I chrono the next 5 rnds there was a ES 57.
I was using win brass. It was not a good lot of brass. So I went to lapua brass and uniformed everything with a lot less work and more time on the range. The same load in the lapua brass cut the ES down to 14. May not fix the problem but this is just what I have experienced with high ES.
German,
I sure agree with you statement on the 223:
'The .223 has been, in my experience, one of the toughest cartridges to get a low ES/SD out of.'
I have more than 1500 rounds over the chronograph with the 223 using 80 / 90 grain bullets, six different powders and three brands of primers.
Very small differences in primers all three shot very good, CCI-BR, Fed 205m, and Rem 7 1.2 BR.
The three best powders were 1. VV-N550, 2. RL-15 and 3. Varget.
Using the N550, Berger 90VLDs and CCI-BRS, I'm getting sub X-ring at 1000 yards,prone, irons).
Summary after cutting barrel from 32†to 30†and to 28â€
100 rounds fired for each length. A mix of 80/90 grain loads.
MV average
32†--------- 30†---------28â€
2989 ------- 2983 ------- 2963
ES average
32†--------- 30†---------28â€
25 ---------- 23 ---------- 30
Jerry
I sure agree with you statement on the 223:
'The .223 has been, in my experience, one of the toughest cartridges to get a low ES/SD out of.'
I have more than 1500 rounds over the chronograph with the 223 using 80 / 90 grain bullets, six different powders and three brands of primers.
Very small differences in primers all three shot very good, CCI-BR, Fed 205m, and Rem 7 1.2 BR.
The three best powders were 1. VV-N550, 2. RL-15 and 3. Varget.
Using the N550, Berger 90VLDs and CCI-BRS, I'm getting sub X-ring at 1000 yards,prone, irons).
Summary after cutting barrel from 32†to 30†and to 28â€
100 rounds fired for each length. A mix of 80/90 grain loads.
MV average
32†--------- 30†---------28â€
2989 ------- 2983 ------- 2963
ES average
32†--------- 30†---------28â€
25 ---------- 23 ---------- 30
Jerry
Upgrades & Donations
This Forum's expenses are primarily paid by member contributions. You can upgrade your Forum membership in seconds. Gold and Silver members get unlimited FREE classifieds for one year. Gold members can upload custom avatars.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.
Click Upgrade Membership Button ABOVE to get Gold or Silver Status.
You can also donate any amount, large or small, with the button below. Include your Forum Name in the PayPal Notes field.
To DONATE by CHECK, or make a recurring donation, CLICK HERE to learn how.