stagpanther
New member
"Statistics don't prove anything, they suggest correlation for decision-making" the immortal words from my professor who taught advanced statistics.
BTW- said friend, he actually ruined what was a mint condition 1980 Cameron turning it into a "race" car. And it's not even all that fast.
pgdion Today 09:30 AM
I have had some very accurate loads that did not exhibit a low SD. And I have had single digit SD loads that had mediocre accuracy. Bet you have, too. It's just one more piece of information.
In my experience a good SD or es is important. However from an accuracy standpoint there are other things at play, depending on how deep down the rabbit hole you want to go. For me I dial in a good es/SD, then tune the seating depth. The ES/SD ensures consistency, and the seating depth tunes the group size.Short answer is SD is meaningless for the purpose of accuracy. What its good for not a clue (I was lucky to manage Algebra). Average is important FPS wise as is the ES (which throws average into the dumpster if its way off, ie, you have a quality control issue).
Yep
Ok, I am shooting up some 270 factory ammo that does not shoot worth diddly in a hunting gun (I have a 270 target barrel as I have been gifted with gobs of 270 bullets and its fun)
Now I am curious on what the variance in accuracy is out of the Target gun (the Sako 270 hunting guns hates factory)
Well the factory in the 270 target pretty well sucks as well. Ok, however, some Winchester Coated plastic tip nickle I gets a nice 3/4 inch group out of (which is the best I can do with the Sako 270 and hand loads though that beats the 2.5 inch factory groups all to hell).
So, 5 shot average is 3140 ES: 46 SD: 19.7.
The previous group was 150 gr Sierra Bullets in a factory load, 2 inch group
Avg: 2927 ES: 21 SD: 8.8
So clearly the 150 gr rounds were hugely better (via SD) even though it was by far the worst group.
Me thinks SD is irrelevant, as I had one shot in another group that was really wild, but it also was 200 FPS lower than the lowest of the other 4. Mmmm me thinks, kind of sucky quality control and I bet it was not the SD!
From what I can see, if your ES is in the 50 range, you done good quality controls wise and see where the holes in the target are.
Now, If I had an ES of 100 and I had a 1/4 group I would be in hog heaven as well. Seems to be for sure under 60-70 for ES and the hell with SD.
Sorry Aguila... I said all that and never answered your question. When I was crunching numbers, I used ten shot strings; mostly because that is what I'd seen done in firearms publications for decades.I've had an old BetaMaster for about 15 years. When I first got it, I was obsessed with extreme spread & standard deviation. At the time I had very accurate and powerful loads I'd been using long before I got the Chrony. My first inclination was to tweak those loads for 'better numbers'. Then I came to my senses and decided to not fix what was working.
These days I use it to see what velocity a given load is producing from a specific firearm. Five shots give me that. If the load is producing velocity range established as safe pressures by published reliable manuals and it produces acceptable accuracy, I'm done. I'm not Jonesing for a Nobel Prize for Ballistic Science. I'm just looking to clobber a groundhog, deer or coyote out across the pasture.
Not quite; standard deviation is a descriptor of spread regardless of the actual distribution shape. With some distributions, Gaussian (or Normal, the "typical" bell curve) it provides a great deal of information (with the mean and standard deviation you can tell what proportion of results will occur within any given range of values). If the actual data is a different shape, such as Uniform distribution (i.e. every outcome occurs with the same probability such a "fair" 6-sided die or flipping an honest coin) not much help.I should add ..... SD is an indication of how likely your data is going to deviate from the average (mean). It's based on typical data fitting a bell curve. Think of how many data points you need to start to shape a bell. It's a lot more than 10. Even 15 is weak. That doesn't mean you need 15 points for good data though. If you have 5 to 10 points and they are all very close, you can be pretty sure the average of those points will give you good results. The SD on that few of points will be pretty meaningless though.
An old Finance professor told me that "statistics are like bikinis, what they reveal is interesting, but what they conceal is vital"!