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reloading for consistent speed? #14200969 10/14/19
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JeffG Offline OP
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I'm try to find the simple logic in the mysterious world of reloading.

in reloading for my hunting rifles I select my bullet for terminal success, either small groups for varmints, or predictable expansion on game animals, then I search for the most consistent load; consistent point of impact, small ES on the chrono, hopefully with similar results at summer temps and winter temps.


Once finding a good load, and I eventually run out of powder, I try another jug of powder, sometimes the same type/new batch, sometimes a different type (less temp sensitive, or one of these new "clean burning/less fouling" types). I use the same rifle, same bullet, same cases, same primer trying to achieve the same velocity I had success with. Once there I get the same consistency only about 50% of the time. It feels like starting load development all over again with every new jug of powder.

My question:
Why wouldn't the best consistency of any rifle/cartridge/bullet combo be the same with any powder that can achieve the same muzzle velocity?


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Re: reloading for consistent speed? [Re: JeffG] #14200976 10/14/19
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Instead of loading for ES, one would be better served loading for standard deviation. It's a much better description of consistency

Re: reloading for consistent speed? [Re: JeffG] #14200999 10/14/19
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Originally Posted by JeffG
I'm try to find the simple logic in the mysterious world of reloading.

in reloading for my hunting rifles I select my bullet for terminal success, either small groups for varmints, or predictable expansion on game animals, then I search for the most consistent load; consistent point of impact, small ES on the chrono, hopefully with similar results at summer temps and winter temps.


Once finding a good load, and I eventually run out of powder, I try another jug of powder, sometimes the same type/new batch, sometimes a different type (less temp sensitive, or one of these new "clean burning/less fouling" types). I use the same rifle, same bullet, same cases, same primer trying to achieve the same velocity I had success with. Once there I get the same consistency only about 50% of the time. It feels like starting load development all over again with every new jug of powder.

My question:
Why wouldn't the best consistency of any rifle/cartridge/bullet combo be the same with any powder that can achieve the same muzzle velocity?


It isn't just the speed of the bullet as it exits the muzzle, it's the timing of its exit relative to whatever dance your barrel does. Different powders can and do produce different acceleration curves, so two loads having the same speed at the muzzle don't necessarily have the same time from the instant of ignition to the exit of the bullet. Just like two drag cars can have the same trap speed but different 1/4 mile times.


"In the real world, think of the 6.5 Creedmoor as the modernized/standardized/optimized version of the 6.5x55/.260." John Barsness 2019
Re: reloading for consistent speed? [Re: JeffG] #14201127 10/14/19
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About the time I think I have figured out how to achieve a small ES with various handloads.........I figure out I don't.........


Casey

Not being married to any particular political party sure makes it a lot easier to look at the world more objectively...
Having said that, MAGA.
Re: reloading for consistent speed? [Re: JeffG] #14201138 10/14/19
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Extreme spread is a very fickle statistic--especially when applied to the relatively few shots in a typical hunter fires when working up loads. Even standard deviation doesn't mean anything when firing a 5-shot string (much less a 3-shot string). Ammunition companies generally fire dozens of rounds when testing for consistent SD.

This still doesn't mean their ammo will always be reasonably accurate in a wide variety of rifles, because the rifles themselves vary too much. But in general there's a better chance of consistent accuracy than the "pet loads" of many handloaders, many of which are based on a single 3-shot group.


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
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Re: reloading for consistent speed? [Re: JeffG] #14201220 10/14/19
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I used to be more concerned about low E.S/S.D..'s. than I am now. I've had rounds with less than desirable variations that shot great. I'm now looking more at the target, but realize, E.S. and S.D. values have merit. May be more important at extreme ranges.

Seems to me that Varget has some of the lowest E.S. values and does very well at the target. I can see why target shooters like it. I know I do.

It can be a fickle business, different powders performing differently in different rounds. So, blanket statements may not have a lot of predictive value, opinions here on the Fire, notwithstanding... blush

grin

DF

Re: reloading for consistent speed? [Re: JeffG] #14201222 10/14/19
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Originally Posted by JeffG
I'm try to find the simple logic in the mysterious world of reloading.

in reloading for my hunting rifles I select my bullet for terminal success, either small groups for varmints, or predictable expansion on game animals, then I search for the most consistent load; consistent point of impact, small ES on the chrono, hopefully with similar results at summer temps and winter temps.


Once finding a good load, and I eventually run out of powder, I try another jug of powder, sometimes the same type/new batch, sometimes a different type (less temp sensitive, or one of these new "clean burning/less fouling" types). I use the same rifle, same bullet, same cases, same primer trying to achieve the same velocity I had success with. Once there I get the same consistency only about 50% of the time. It feels like starting load development all over again with every new jug of powder.

My question:
Why wouldn't the best consistency of any rifle/cartridge/bullet combo be the same with any powder that can achieve the same muzzle velocity?


As others have stated, acceleration of the bullet to the muzzle (this varies with the powder used, dimensions of the bore and/or bullet and start pressure). Case fill is another consideration (>95%, avoid 100% as some cases will be compressed and some not, and generally < 105%) so two zones for case fill. Seating primers in a consistent manner helps ES ( I pre-load the cup to the anvil) the thinking here is mitigation of an inconsistent firing pin strike. I get better / lower ES with cases once fired from annealing ( this points to my inconsistent annealing processes). Concentricity of the loaded round must be 0.000" run-out, if not , find out where in the load process that induces run-out, (this will lead you to using a body die and a Lee collet neck size die).

Depending on whether the cartridge is over-bore, like a 22-300 Weatherby as a gross example, barrel erosion must be accounted for. You will see this as velocity dropping off a bit, groups opening up.....essentially losing your tune. An increase in powder usually help here. Bottom line here is that your load over time must be dynamic to the changing 'mechanics' of your rifle and environment that it is operated in.

A LabRadar is a great tool for tracking velocities, my dedicated bench guns are velocity recorded for nearly every round. This gives me a better over-all picture as to what is going on , state of tune and how the environment affects things.
The study of QuickLoad answers a lot of questions about the 'mysteries' of internal ballistics. If you go that route I've found printing off the manual helps immensely in this regard.

The same regime is followed for my hunting loads, the only difference is that a light factory crimp is applied for the sake of reliability in the field.

Re: reloading for consistent speed? [Re: JeffG] #14201364 10/14/19
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Range (what shooters call ES) is directly convertible to standard deviation. As stated earlier, estimates at variation based on small samples can quite far off.


I don't associate with snobby people. I'm much too good for that.
Re: reloading for consistent speed? [Re: denton] #14201379 10/14/19
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Denton,

Of course--but many of the handloaders I have been acquainted with only record the fastest and slowest shots in their notes. (In fact, a few only record the fastest shot, just like many only shoot one group with a certain load, and call load "development" good.)


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
Re: reloading for consistent speed? [Re: denton] #14201393 10/14/19
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Originally Posted by denton
Range (what shooters call ES) is directly convertible to standard deviation. As stated earlier, estimates at variation based on small samples can quite far off.


I'm not a statistician, but having been a theorem proving mathematician in a prior life I "feel a disturbance in the force" when I see something like that stated without the caveat hypotheses. grin


"In the real world, think of the 6.5 Creedmoor as the modernized/standardized/optimized version of the 6.5x55/.260." John Barsness 2019
Bravo

Re: reloading for consistent speed? [Re: denton] #14201482 10/14/19
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Originally Posted by denton
Range (what shooters call ES) is directly convertible to standard deviation. As stated earlier, estimates at variation based on small samples can quite far off.


Isn't that what the buttons on a calculator are for? grin

Been awhile ago, someone posted a factor to multiply the results of less than a ten shot groups. Do you have those numbers Denton?

Nice thing about the electronic targets people are migrating to, they give you a velocity at the target. Shot Marker also gives you a SD for your string. I haven't researched the accuracy of the numbers.

Re: reloading for consistent speed? [Re: AJ300MAG] #14201568 10/14/19
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Gotta be quick... only have about 10 minutes.

The conversion factor is the d2 constant, which is an old shortcut method for quickly estimating standard deviation. It is widely used to set three standard deviation limits in Control Charts, and has been for about 100 years.

For small groups of data, say 5 items, it is very nearly as efficient as standard deviation, and does not have the problem of systematically underestimating variation. By the time you get to groups of 10, its efficiency is beginning to fall off quite a bit.

There are several ways to estimate standard deviation, and typically none of them will give exactly the same answer. However, most of them will provide decent accuracy.

To convert range to SD, you divide range by the d2 constant:

For groups of 2, d2=1.128. For 3, 1.693. For 4,2.059. For 5, 2.326. I'll post the rest after my meeting.


I don't associate with snobby people. I'm much too good for that.
Re: reloading for consistent speed? [Re: denton] #14201590 10/14/19
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Originally Posted by denton
Gotta be quick... only have about 10 minutes.

The conversion factor is the d2 constant, which is an old shortcut method for quickly estimating standard deviation. It is widely used to set three standard deviation limits in Control Charts, and has been for about 100 years.

For small groups of data, say 5 items, it is very nearly as efficient as standard deviation, and does not have the problem of systematically underestimating variation. By the time you get to groups of 10, its efficiency is beginning to fall off quite a bit.

There are several ways to estimate standard deviation, and typically none of them will give exactly the same answer. However, most of them will provide decent accuracy.

To convert range to SD, you divide range by the d2 constant:

For groups of 2, d2=1.128. For 3, 1.693. For 4,2.059. For 5, 2.326. I'll post the rest after my meeting.



Thank you sir!

Re: reloading for consistent speed? [Re: JeffG] #14201742 10/14/19
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OK... out of the meeting now.

For 6, 2.534. For 7, 2.704. For 8, 2.874. For 9, 2.97. For 10 3.078.


I don't associate with snobby people. I'm much too good for that.
Re: reloading for consistent speed? [Re: JeffG] #14201753 10/14/19
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When one is operating at around 55,000 psi in a tiny chamber, very minor variables can become quite significant. I have and use a 30-378. One more grain of powder in my loads and I get near every possible indication of pressure.


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Re: reloading for consistent speed? [Re: 1minute] #14202211 10/14/19
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Originally Posted by 1minute
When one is operating at around 55,000 psi in a tiny chamber, very minor variables can become quite significant. I have and use a 30-378. One more grain of powder in my loads and I get near every possible indication of pressure.


You are talking Weatherby here, that is a whole different can of worms that Denton might not even be able to sort out 🤔😀

Re: reloading for consistent speed? [Re: JeffG] #14202403 10/14/19
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Aren't these math questions on the SAT test?


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Re: reloading for consistent speed? [Re: JeffG] #14202474 10/14/19
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Is this really so "unknown"?

The techniques for loading accurate benchrest rounds have been known and written about for a long time: Brass of consistent weight and dimensions, especially neck diameter. Bullets that are consistent in weight, and more importantly dimensions, especially neck thickness. Powders that perform consistently in different temperatures (a full case helps, even with other powders) and sometimes playing with primers to see which one results in the finest accuracy. (Yes, this still CAN make a diffference.) Then there's playing with seating depth, which often is more important than powder charge.

Plus, there;s the chronograph factor. Some provide more accurate results than others, but over the past year I ran a test with several chronographs ranging in price from around $100 to $500+. All except one resulted in the same average velocity, within less than 10 fps. This was while chronographing the same loads at the same time, with the chronographs set up together.


“Montana seems to me to be what a small boy would think Texas is like from hearing Texans.”
John Steinbeck
Re: reloading for consistent speed? [Re: mathman] #14202938 10/14/19
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Originally Posted by mathman
Originally Posted by denton
Range (what shooters call ES) is directly convertible to standard deviation. As stated earlier, estimates at variation based on small samples can quite far off.


I'm not a statistician, but having been a theorem proving mathematician in a prior life I "feel a disturbance in the force" when I see something like that stated without the caveat hypotheses. grin


I could be wrong, but I think denton's statement is correct if we assume a normal distribution. Problem is, that's a poor assumption for this stuff. I've seen plenty of results in shooting that do not fit a normal distribution at all, with all sorts of common causes like mixed headstamp brass, mixed batches of components, etc. Theory like this falls apart when the assumptions don't match reality.

I don't worry about ES too much other than as an indication of inconsistent powder burn at low pressures. Otherwise I go by results on target and fine tune as needed.

Re: reloading for consistent speed? [Re: JeffG] #14202989 10/14/19
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It actually doesn't require a normal distribution. If special causes like barrel rubs and shooter flinch have been eliminated, so that variation is random, then it will give about the same answer as calculating SD by its definition, the sum of squares. If special cause is present, then the classic sum of squares route will give a higher number.

Standard deviation is a measure of variation.

Range is a measure of variation.

They are different measures of the same thing, and can be converted back and forth. If the subgroups have few items, the conversion is pretty good.

If you are shooting five shots, range is about as good a number as you can get.


I don't associate with snobby people. I'm much too good for that.
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