This happened to me yesterday. SD of 5.3 FPS and extreme spread of 12.8 FPS was the largest group with one of my 308 rifles.
That said, I may go back and tweak the seating and see what's what.
Originally Posted by dave7mm
Originally Posted by rost495
What I will state is that almost every last time I was shooting at 600 yards and watched the chrono the load that produced the lowest ES and SD and then went and looked at the holes in the paper I was never happy. The lowest ES and SD just never produced best accuracy. .
+1
dave
“Live free or die. Death is not the worst of evils.” - General John Stark.
I want mine as low as possible, under 10 fps with 3 shot groups. That doesn’t mean “squat” at close range, say under 400 yards, but gets exponentially more important at long ranges! JMO memtb
Last edited by memtb; 02/23/24.
You should not use a rifle that will kill an animal when everything goes right; you should use one that will do the job when everything goes wrong." -Bob Hagel
“I’d like to be a good rifleman…..but, I prefer to be a good hunter”! memtb 2024
I start out with 5s when looking for promising data with the chrony. The promising ones get repeated with 10 shots to confirm. Then its seating depth checks with 5s @ 100 yards. Final range checks are at either 200 or 300 yards.
I currently have 2 loads that are neck and neck for going into the recipe log, so next week it's 15 rounds each at 200 or 300 yards (depending on however busy the range is) to decide.
Then when the snow clears I'll be in the hills where I check 'em again at 400 yards. I can always get to within 400 yards at whatever I'm looking at in the crosshair.
It's you and the bullet, and all the rest is secondary.
I want mine as low as possible, under 10 fps with 3 shot groups. That doesn’t mean “squat” at close range, say under 400 yards, but gets exponentially more important at long ranges! JMO memtb
ES or SD?
SD estimates from three shots are not reliable at all.
I've read where some find the best ES (lowest) and then adjust seating depth to get the best group out of that ES. Is that real/fake etc - this is coming from F class guys.
This absolutely works. I was experimenting with ammo for a new F-T/R build last week. The load that gave the best ES and SD produced mediocre groups. I started playing with seating depth and managed to make three consecutive 1/2 MOA ten shot groups. I ran them all on the chronograph after tuning depth, and for the 30 rounds ES was 14 and SD was 5.2. I was quite happy. First match of the season is in two weeks.
"Full time night woman? I never could find no tracks on a woman's heart. I packed me a squaw for ten year, Pilgrim. Cheyenne, she were, and the meanest bitch that ever balled for beads."
I start out with 5s when looking for promising data with the chrony. The promising ones get repeated with 10 shots to confirm. Then its seating depth checks with 5s @ 100 yards. Final range checks are at either 200 or 300 yards.
I currently have 2 loads that are neck and neck for going into the recipe log, so next week it's 15 rounds each at 200 or 300 yards (depending on however busy the range is) to decide.
Then when the snow clears I'll be in the hills where I check 'em again at 400 yards. I can always get to within 400 yards at whatever I'm looking at in the crosshair.
Sometimes I will shoot two or three rounds of each load to just rule out what doesn't work.
"Full time night woman? I never could find no tracks on a woman's heart. I packed me a squaw for ten year, Pilgrim. Cheyenne, she were, and the meanest bitch that ever balled for beads."
In my mind - low ES/SD is an indicator of consistency in combustion. A bullet that consistently moves at the same speed is probably going to print the more consistent group time after time. Not saying the most PRECISE group but whatever it produces, it's likely to do that over and over given the nature of always sending a bullet at 2700 or whatever.
Once small ES/SD is found - then change things to find a way to make that group more precise? Seating depth seems to be the way some do it.
Which - assuming it's factual, makes sense to me. Give me the most consistent and repeatable results first and then we'll make those results better. I don't know how you can consistently make precise groups IF your velocity's ES is large.
In my experience, which is primarily with shotguns at a competitive level - consistency is paramount. So ES/SD being consistently low gives me the best chance of seeing repeatable groups (regardless of how precise they may be).
Take your minimum velocity and maximum velocity, run them through a ballistics program. Look at the difference in the drop values for both velocities at 600 and 1000 yards, it will give you an idea if you can hold your shots in the X ring.
I want mine as low as possible, under 10 fps with 3 shot groups. That doesn’t mean “squat” at close range, say under 400 yards, but gets exponentially more important at long ranges! JMO memtb
ES or SD?
SD estimates from three shots are not reliable at all.
ES!
Understood, but while doing load development and increasing 1 grain/3 shot group….very small velocity gains with each group having very tight ES’s. This was repeated for 3 or 4 load increases.
Maybe not as reliable as a very long shot string, but the groups were nearly superimposed over each other and around 1/2” for each 3 shot group. Considering it’s a rather light rifle, producing near 60 ft/lbs felt recoil….I was satisfied! With the cost and limited components available….. I guess that I’m easy to please! After all…..it’s a hunt’n rifle, not a BR rifle! 😉 memtb
Last edited by memtb; 02/23/24.
You should not use a rifle that will kill an animal when everything goes right; you should use one that will do the job when everything goes wrong." -Bob Hagel
“I’d like to be a good rifleman…..but, I prefer to be a good hunter”! memtb 2024
I see this noted above. How is this being measured?
I've seen some examples where a load cell is used to measure what could be this parameter. That unit of measure is a force to insert a bullet into case neck.
I suppose a mathematical equation could be used to derive a neck tension value whatever that is.
Some use force, some use the difference of outside diameter after sizing and spring-back before and after seating a bullet.
"Full time night woman? I never could find no tracks on a woman's heart. I packed me a squaw for ten year, Pilgrim. Cheyenne, she were, and the meanest bitch that ever balled for beads."
The ES and SD numbers are indications of consistency only, not accuracy. If you get the numbers to coincide with accuracy, that's great, but don't count on that happening. Lots of others factors make up an accurate load. Group size first (five, five-shot groups, at least), then the numbers, if you have to have them. I seldom look at the numbers, something that has become quite a fad in recent years, along with neck tension.
Yep, a minimum of 30 is what a major American ammunition factory uses when working up loads with a new batch of powder.
Yep.
30 is generally considered the minimum threshold for a valid statistical SD.
Less may be somewhat indicative, but is not definitive.
Guys that shoot 3 or 5 round groups & think that the the data is gospel are just fooling themselves.
MM
Agree, 100%.
"Full time night woman? I never could find no tracks on a woman's heart. I packed me a squaw for ten year, Pilgrim. Cheyenne, she were, and the meanest bitch that ever balled for beads."
From a different angle. Anything is possible some things are more probable. measurement is a combination of systematic and random errors. ES and SD are part of the systematic or Gaussian side and the reloader has some control over them. Both the sighting system and the physical system of the rifle assembly are non-linear and the optimum combination lies in a"basin of attraction" for all the inputs. Both manufacturers and shooters try to linearize the system optimizing the many components involved. When in fact a random error (ex. change in temp. and burn rate of a powder) can offset one or more of the systematic error as to cancel both, and show the resultant value closer to the midline of the Gaussian distribution or completely ruin any kind of correlation between the two (large groups). Bench shooting assumes the some linear approach, (your going to do it the same every time). The uncontrollable factors in long range shooting make it surprising the whole thing works as well as it does.
The most important part of the entire thing is : Have Fun!!
These discussions always bring to mind this from Ken Oehler that leapt out at me from the manual for my 35P purchased decades back:
Quote
Whenever you use standard deviation, remember there is an important corollary of Murphy's law. Its regular use can replace many mathematical theorems and complicated statistical procedures.
Large groups usually repeat;
Large groups with large standard deviations always repeat;
Small groups caused by luck never repeat.
You can no more tell someone how to do something you've never done, than you can come back from somewhere you've never been...
The ES and SD numbers are indications of consistency only, not accuracy. If you get the numbers to coincide with accuracy, that's great, but don't count on that happening. Lots of others factors make up an accurate load. Group size first (five, five-shot groups, at least), then the numbers, if you have to have them. I seldom look at the numbers, something that has become quite a fad in recent years, along with neck tension.
Again, this is just talk/theory discussion during crap weather seasons and a lack of game to shoot.
And that's my question - can you be consistently accurate and precise without consistency of load (as measured by large or not ES/SD)?
Can you more likely repeat accurate and precise loads with inconsistent velocities that vary greatly or is it more likely that if you find a consistent load in ES/SD - make it accurate?
And yes, I'm familiar with Audette for finding the best "load". I'm more interested in this theory I've seen promulgated by guys like F-Class John and Cortina as part of their "don't care where the lands are and I don't keep that relationship a 1:1" mentality and load development that way. Cortina is obviously a well credentialed shooter.
(Selecting some level of "jump" and then finding the powder/charge that works with that is a bit of a backwards play on that I guess)
I never was that involved in the testing. Our targets where forgiving and we had to work on us almost more than the load.
Class took a lot of the human error out and demanded a smaller target.
Its good to read these things.
The 2 things that I did that may not apply anymore at all. But at least one seemed repeatable to me.
I found the distance off the lands that the groups were happy. Seemed to be pretty reliable after I had worn out enough barrels that I could just kind of ignore it and all would be good enough. I did have a rule and it was to either be off the lands or engaged. Never give or take within about .015 of the lands. In English I was at least .016 off the start of the lands best I could tell or I was engaged at least .015 or more. I think my memory is right. But since the ogive of bullets vary sometimes from bullet to bullet, hopefully not much, but they do, I didn't want to be right at that pressure making engaged and have one less or one more so to speak. It is one reason we seat off the ogive and not so much the OAL actually.
Once I had loss of accuracy I went back to the chrono and usually had lost speed, which would mean getting out of the node IMHO. So ad powder until back at original happy speed. At that point readjust the seating depth to the same relationship it was.
I'm gonna have to google and read when I have time. I cannot see why you would not chase both the speed and the seating depth as the throat wears but I never did just one or the other so it was not a real experiment so to speak.
Great read. Good topic. Glad you brought it up. Glad I get to learn.
Primers though.... if you get a great load stash that lot of primers. Changes in powder lots I could usually make work... primer changes not so much...
We can keep Larry Root and all his idiotic blabber and user names on here, but we can't get Ralph back..... Whiskey Tango Foxtrot, over....
Rost - that's a good point, I think it's a lot of which end of the stick you approach from. I'd be shocked if the best/most consistent load also wasn't one that showed it in ES/SD for those components selected.
How you arrive at it - might not matter. Or you might not even measure it but are "there". I know a lot of people who don't own a chrony. Shoot at 100, shoot at say 600 - measure the drop and plug into software to arrive at what their speed must be - if they have utmost confidence in the BC being accurate.
It's all another way to catch fish I guess. Just wanted conversation that was deeper than cartridge comparisons.
ES/SD are a measure of something that has already happened, not what can happen. They are a math relationship of systematic errors, nothing more or less, they exist whether you want to look at them or not. Your are asking if following the procedure to get what you like in them will repeat the same result. The answer is yes if you repeat the random errors the same way, which you can't -- thats why they are called random
