Precision Reloading

[AlaskaHunter]

I am a big fan of Erik Cortina.
He posted this youtube video about a week ago
Precision Reloading is easy. You complicate it!

 

[VikingsGuy]

Good post. The part that gets me about so much reloading “info” is how little actual statistically validated data is there to support the various “beliefs”. To compare primer brands against one another to “see” a true difference between 1.0 MOA and 0.75 MOA will require shooting between 50-70 identical rounds of each. Anything less than 5 groups of 10 to compare and you might as well flip a coin. But some guy shots 2 3-shot groups with brand X and 2 3-shot groups with brand Y and then spends the next 10 years telling anyone who will listen to that Brand X absolutely is the better primer. Here is a good link to start going down this rabbit hole: https://www.autotrickler.com/blog/practical-statistics-for-shooters

 

[AlaskaHunter]

Good post. The part that gets me about so much reloading “info” is how little actual statistically validated data is there to support the various “beliefs”. To compare primer brands against one another to “see” a true difference between 1.0 MOA and 0.75 MOA will require shooting between 50-70 identical rounds of each. Anything less than 5 groups of 10 to compare and you might as well flip a coin. But some guy shots 2 3-shot groups with brand X and 2 3-shot groups with brand Y and then spends the next 10 years telling anyone who will listen to that Brand X absolutely is the better primer. Here is a good link to start going down this rabbit hole: https://www.autotrickler.com/blog/practical-statistics-for-shooters

Good stuff: " A tight group is nice to have, but at long range, it pales in comparison to your velocity variation".
I wonder how many times my tight group or poor group was due to me and human error....
same load some days excellent 5 or 10-shot group, other days same load not so much, but the velocity standard deviation is nearly the same.

 

[homers]

I wonder how many times my tight group or poor group was due to me and human error....

Can’t be the shooter. From what I’ve read on many forums, everyone shoots sub MOA

 

[N2TRKYS]

Good post. The part that gets me about so much reloading “info” is how little actual statistically validated data is there to support the various “beliefs”. To compare primer brands against one another to “see” a true difference between 1.0 MOA and 0.75 MOA will require shooting between 50-70 identical rounds of each. Anything less than 5 groups of 10 to compare and you might as well flip a coin. But some guy shots 2 3-shot groups with brand X and 2 3-shot groups with brand Y and then spends the next 10 years telling anyone who will listen to that Brand X absolutely is the better primer. Here is a good link to start going down this rabbit hole: https://www.autotrickler.com/blog/practical-statistics-for-shooters

You’ve never had a primer change tighten groups for a certain load?

 

[VikingsGuy]

You’ve never had a primer change tighten groups for a certain load?

I’m saying I rarely shoot enough repetitions to know if there was actually scientifically valid tightening, or just saw the illusion of a tightening. I am not saying primers can‘t make a difference, I am saying the average reloader doesn’t shoot enough repetitions to see any such difference with any statistical probability.

For example, is the primer used for Group #1 better than the one used for Group #7? Actually, its the same primer and the two groups are just two 5 subsets of 50 rounds shot with the same exact ammo.

 

[N2TRKYS]

I’m saying I rarely shoot enough repetitions to know if there was actually scientifically valid tightening, or just saw the illusion of a tightening. I am not saying primers can‘t make a difference, I am saying the average reloader doesn’t shoot enough repetitions to see any such difference with any statistical probability.

For example, is the primer used for Group #1 better than the one used for Group #7? Actually, its the same primer and the two groups are just two 5 subsets of 50 rounds shot with the same exact ammo.

View attachment 151904

That doesn’t look like the primers fault. I’ve had different primers tighten loads up that I wouldn’t have used without changing them. Different cartridges have liked different primers. I don’t think it’s always been the same brand.

 

[VikingsGuy]

Good stuff: " A tight group is nice to have, but at long range, it pales in comparison to your velocity variation".

I agree with the premise of the video you posted - velocity variation is an indication of consistent brass prep, powder measurement, powder consistency and primer quality, while group size is a combination of velocity variation AND barrel harmonics - so velocity variation is only half of the picture - you still need to get the barrel harmonics right. Having only one (fps es/sd or barrel node) right may look OK at 100y, but having only one right will always fall apart as you extend the range.

 

[VikingsGuy]

That doesn’t look like the primers fault. I’ve had different primers tighten loads up that I wouldn’t have used without changing them. Different cartridges have liked different primers. I don’t think it’s always been the same brand.

I don‘t think I am making my point clearly - my point is unless you shoot a minimum 30 rounds (preferably 60) of the identical ammo for each of the two primers you have no statistically valid evidence of one being better than the others (unless one is horribly off) - no matter what you are “intuitively” seeing on paper.

 

[N2TRKYS]

I don‘t think I am making my point clearly - my point is unless you shoot a minimum 30 rounds (preferably 60) of the identical ammo for each of the two primers you have no statistically valid evidence of one being better than the others (unless one is horribly off) - no matter what you are “intuitively” seeing on paper.

Idk, man. It just keeps hitting where I’m aiming. That’s all I’m interested in.

 

[44hunter45]

I agree with the premise of the video you posted - velocity variation is an indication of consistent brass prep, powder measurement, powder consistency and primer quality, while group size is a combination of velocity variation AND barrel harmonics - so velocity variation is only half of the picture - you still need to get the barrel harmonics right. Having only one (fps es/sd or barrel node) right may look OK at 100y, but having only one right will always fall apart as you extend the range.

It is my opinion that many shooters who say they are getting X sized groups at 300 yards have never been to a 300 yard range. They are extrapolating from groups they shot at 100 yards. Even here in Idaho a 300+ yard controlled shooting location can be difficult to find. Here in our county, the only 200+ location was gated up without reason or comment. I used to shoot out to 600 there. No more. It's now 90 miles to a good covered range with solid tables where we can go long.

 

[Deleted member 16014]

Love me some stats. Run a pilot to get SD and means for each sample population (primer A and primer B), run power analysis —dime a dozen online — will tell you number of samples required at whatever alpha you want. Then you’ll have gone crazy and probably just switch to fishing.

 

[AlaskaHunter]

This may be getting in the weeds, but my background is in statistics for research.
Assume that each shot is from a population of shots with a bell-shaped distribution peaking at the mean.

Say you shoot a 10-shot group today, with an average muzzle velocity of 2900 fps, standard deviation of 10 fps.
You try a different load the next day, 10-shots with an average muzzle velocity of 2850 fps, standard deviation of 10 fps.
Is the first day's load significantly faster than the second day's load? Yes
The 90 percent confidence interval is 40 to 60 fps based on these 2 sample days with the sample difference of 50 fps.

Say you shoot a 10-shot group today, with an average error of 0.50 inches, standard deviation of 0.10 inch.
You try a different load the next day, 10-shots with an with an average error of 0.70 inches, standard deviation of 0.10 inch.
Is the first day's group significantly tighter than the second day's group? Yes
The 90 percent confidence interval is .10 to .30 inches with the sample difference in means of 0.20 inch.

Say you shoot a 10-shot group today, with an average error of 0.70 inches, standard deviation of 0.50 inch.
You try a different load the next day, 10-shots with an with an average error of 0.90 inches, standard deviation of 0.50 inch.
Is the first day's group significantly tighter than the second day's group? No, there is too much variation.
The 90 percent confidence interval is -27 to +.67 inches

 

[N2TRKYS]

This may be getting in the weeds, but my background is in statistics for research.
Assume that each shot is from a population of shots with a bell-shaped distribution peaking at the mean.

Say you shoot a 10-shot group today, with an average muzzle velocity of 2900 fps, standard deviation of 10 fps.
You try a different load the next day, 10-shots with an average muzzle velocity of 2850 fps, standard deviation of 10 fps.
Is the first day's load significantly faster than the second day's load? Yes
The 90 percent confidence interval is 40 to 60 fps based on these 2 sample days with the sample difference of 50 fps.

Say you shoot a 10-shot group today, with an average error of 0.50 inches, standard deviation of 0.10 inch.
You try a different load the next day, 10-shots with an with an average error of 0.70 inches, standard deviation of 0.10 inch.
Is the first day's group significantly tighter than the second day's group? Yes
The 90 percent confidence interval is .10 to .30 inches with the sample difference in means of 0.20 inch.

Say you shoot a 10-shot group today, with an average error of 0.70 inches, standard deviation of 0.50 inch.
You try a different load the next day, 10-shots with an with an average error of 0.90 inches, standard deviation of 0.50 inch.
Is the first day's group significantly tighter than the second day's group? No, there is too much variation.
The 90 percent confidence interval is -27 to +.67 inches

If primer brand x was always a 2” group everytime you shot it and primer brand y was always a 1/2” group everytime you shot it, which one would you choose for your more accurate load?

 

[AlaskaHunter]

If primer brand x was always a 2” group everytime you shot it and primer brand y was always a 1/2” group everytime you shot it, which one would you choose for your more accurate load?

Look at the youtube video posted at the start of this thread: Precision Reloading is easy. You complicate it!

Combustion variation: typical causes variable neck tension, primer variation, type or variation in powder, variation in case capacity.
So when comparing primers, chronograph data are your friend...which primer consistently yields the lowest standard deviation in muzzle velocity?

 

[mtmuley]

Hey Alaska, you ever shoot the Hammers you ordered? mtmuley

 

[std7mag]

If you want to know what has actual affect at distance, look no further than Bryan Litz.
Cheif ballistician at Berger, and his own books/lectures for Applied Ballistics.

He's tried all kinds of crazy combos, just to see what they do.

 

[Flyingone]

What all of you are forgetting, and DOES play a LOT in bullet Travel is the Density, Humidity, Temperature and barometric pressure (witch changes second to second) of the atmosphere! STOP splitting hairs!! If you use the same Primers, Powder Drop, Bullet, etc. your eliminating EVERYTHING YOU HUMANLY CAN BUT the Shooter!! Stop acting like teenage, JR High idiots!! WOW! I can hit PAPER 1/16" better than you! This train of thought is idiotic! Uneducational and unrealistic! Who gives a Rats Harry ass! AN Elk's kill zone is 18 INCHES!!! That is a foot and a half for those that don't know and want to compare primers. OMFG!!! Get a life and talk about REAL stuff like how B.C. on the same bullet weight, elevation or temperature of what you sighted your rifle in at affects your bullet flight 1000X more than what friggen primer you use! GET A LIFE! Talk real Physics or STFU!

 

[Doublecluck]

Huh! Anyhow, so there’s an abundance of ballistic apps now days, I prefer Hornady 4dof as it takes all possible variables in to account. Just one part of consistently making 1k and beyond shots.

I tend to agree with this guy, I’ve never sorted/weighed brass, case capacity, etc., etc, etc. Just quality dies (Redding/Forster) bullets (Berger) brass (Norma,lapua, and most recently atlas) quality primers (I use federal) , and quality powder (among others). Start there and getting low es and sd is pretty easy.


Gonna try this one tomorrow if the mirage isn’t bad, supposed to be a little cooler.

 

[Deleted member 16014]

What all of you are forgetting, and DOES play a LOT in bullet Travel is the Density, Humidity, Temperature and barometric pressure (witch changes second to second) of the atmosphere! STOP splitting hairs!! If you use the same Primers, Powder Drop, Bullet, etc. your eliminating EVERYTHING YOU HUMANLY CAN BUT the Shooter!! Stop acting like teenage, JR High idiots!! WOW! I can hit PAPER 1/16" better than you! This train of thought is idiotic! Uneducational and unrealistic! Who gives a Rats Harry ass! AN Elk's kill zone is 18 INCHES!!! That is a foot and a half for those that don't know and want to compare primers. OMFG!!! Get a life and talk about REAL stuff like how B.C. on the same bullet weight, elevation or temperature of what you sighted your rifle in at affects your bullet flight 1000X more than what friggen primer you use! GET A LIFE! Talk real Physics or STFU!

I don’t have anything to say I just want everyone to enjoy this gem a second time.