Long Range Hunting Online Magazine


Go Back   Long Range Hunting Online Magazine > Rifles, Reloading, Optics, Equipment > Reloading

Reloading Techniques For Reloading


Reply

Chronograph recomendations

 
LinkBack Thread Tools Display Modes
  #36  
Old 05-25-2008, 11:14 AM
Silver Member
 
Join Date: Mar 2008
Location: Chatham, VA
Posts: 436
My M2 will not calculate SD on less than a 5 shot sample. It will of course do ES, thats just subtraction.

I never saw it as that relevant because SD on a sample that small is not very valid anyway. I also tend to use ES as my measure of a loads consistency because it is both a tougher standard and more relevant measure anyway.
__________________
"My greatest fear is that after my demise my wife will sell my guns for the price I told her I paid for them"
-don't know where it came from...but true
Reply With Quote
  #37  
Old 05-25-2008, 01:33 PM
Platinum Member
 
Join Date: Sep 2004
Location: on the rifle range in Utah
Posts: 2,720
Quote:
Originally Posted by Forester View Post
My M2 will not calculate SD on less than a 5 shot sample. It will of course do ES, thats just subtraction.

I never saw it as that relevant because SD on a sample that small is not very valid anyway. I also tend to use ES as my measure of a loads consistency because it is both a tougher standard and more relevant measure anyway.


I have to disagree on several points. The 3 shot group has plenty of validity to it especially when you re-test that load again and it proves itself over. On magnum rifles with skinny barrels, this is pretty well the only method to use as the barrel heats up you can get bad data from a 5 shot group especially in warm weather. I have seen many people toss out "bad loads" with 5 shot groups because the last two shots went faster and in reality, the load could have been fine.

I also disagree that ES is a better measure of the uniformity of the load. The SD and ES are certainly related but the SD is a better "overall" indicator of the deviation from the norm just like it is named. Or in other words, the ES is the window of velocity but the SD is the variation found in that window.
__________________
Find it
Range it
Click it
Pull it
Dump it

If it's not far, it's boring.
Reply With Quote
  #38  
Old 05-25-2008, 10:39 PM
Silver Member
 
Join Date: Mar 2008
Location: Chatham, VA
Posts: 436
Quote:
Originally Posted by goodgrouper View Post
I have to disagree on several points. The 3 shot group has plenty of validity to it especially when you re-test that load again and it proves itself over. On magnum rifles with skinny barrels, this is pretty well the only method to use as the barrel heats up you can get bad data from a 5 shot group especially in warm weather. I have seen many people toss out "bad loads" with 5 shot groups because the last two shots went faster and in reality, the load could have been fine.

I also disagree that ES is a better measure of the uniformity of the load. The SD and ES are certainly related but the SD is a better "overall" indicator of the deviation from the norm just like it is named. Or in other words, the ES is the window of velocity but the SD is the variation found in that window.
If you re-test the load then you have effectively increased the sample size. For magnum loads or any load that heats the barrel too much I would just suggest waiting to let the barrel cool to the same point to prevent heat from changing the results.

I would not consider a sample of 3 to represent with any significant level of confidence the performance of a large number of rounds. You can get pretty deep into the statistics involved but to predict the performance of a large number of rounds, say 100, you need to test more than 3.

I am not saying SD is not a valid way to measure a loads consistency, simply that low ES is a tougher standard to meet, like using a 5 shot group instead of 3. My reason for using ES is mostly this; SD is a statistical way to predict deviation from the norm given a certain data set, ES is the actual observed velocity spread. I place more value on my actual measured numbers than on a prediction.

I don't mean to say that ES is the whole story, I suppose you could have a load with very consistent velocities but once in awhile throws one shot 100fps high or low...both the SD and ES might be fine, but I would not trust it.

The bottom line I think is you have to test and test and test to be sure that you won't get some unpleasant surprise on the shot that counts.
__________________
"My greatest fear is that after my demise my wife will sell my guns for the price I told her I paid for them"
-don't know where it came from...but true
Reply With Quote
  #39  
Old 05-25-2008, 11:53 PM
Platinum Member
 
Join Date: Sep 2004
Location: on the rifle range in Utah
Posts: 2,720
Quote:
Originally Posted by Forester View Post
If you re-test the load then you have effectively increased the sample size. For magnum loads or any load that heats the barrel too much I would just suggest waiting to let the barrel cool to the same point to prevent heat from changing the results.

I would not consider a sample of 3 to represent with any significant level of confidence the performance of a large number of rounds. You can get pretty deep into the statistics involved but to predict the performance of a large number of rounds, say 100, you need to test more than 3.

I am not saying SD is not a valid way to measure a loads consistency, simply that low ES is a tougher standard to meet, like using a 5 shot group instead of 3. My reason for using ES is mostly this; SD is a statistical way to predict deviation from the norm given a certain data set, ES is the actual observed velocity spread. I place more value on my actual measured numbers than on a prediction.

I don't mean to say that ES is the whole story, I suppose you could have a load with very consistent velocities but once in awhile throws one shot 100fps high or low...both the SD and ES might be fine, but I would not trust it.

The bottom line I think is you have to test and test and test to be sure that you won't get some unpleasant surprise on the shot that counts.

Waiting for a 5 shot string when it won't tell you much more than a 3 shot string is very hard to do sometimes. I run a fully operational ballistics lab and I simply don't have all day to wait for barrels to cool down from five shot strings. So I do three and I have never had any gun not hit a 22" gong at 1000 yards using load development methods with 3 shots strings. If the load won't get a low sd on the first go around, it gets left out. BUt if it does, and produces good accuracy and is in a node, it gets re-tested on another day. In this way, I quickly narrow down what load the gun wants without shooting another 60% more ammo down the barrel.

ANd in the world of statistics, standard deviation is the function used mainly and for good reason. It's predictions are much more valuable especially on large quantities of data with similar factors. You could have one shot out of 50 go up in speed 100 fps and you're ES would be horrible. But the SD would show that there was something up with that one round like an extra thick neck, carbon build up, bad charge and so on but the load is still good.

Like I said earlier, ES and SD are related and for all purposes pertaining to our needs, either work fine if you know what to look for.
__________________
Find it
Range it
Click it
Pull it
Dump it

If it's not far, it's boring.
Reply With Quote
Reply

Bookmarks

Thread Tools
Display Modes


Similar Threads for: Chronograph recomendations
Thread Thread Starter Forum Replies Last Post
6.5 Bullet Recomendations Dano5001 Rifles, Bullets, Barrels & Ballistics 17 11-30-2011 11:22 AM
Tripod recomendations mtelkhntr78 Long Range Scopes and Other Optics 6 04-30-2011 11:58 AM
Millennium Chronograph Versus Pact MK IV Timer & Chronograph Eaglet General Discussion 10 03-31-2010 11:28 PM
WY/MT/ID trip recomendations Forester West 5 06-12-2008 06:26 AM
Beyond Recomendations? littletoes Equipment Discussions 5 04-28-2002 09:20 AM


All times are GMT -5. The time now is 09:09 AM.


Powered by vBulletin ©2000 - 2014, Jelsoft Enterprises Ltd.
Content Management Powered by vBadvanced CMPS
All content ©2010-2014 Long Range Hunting, LLC