Cold bore zero versus (very) Hot bore zero “test”

[Formidilosus]

I am not sure if this has been asked before but for hunting purposes , would multiple 3 shot cold bore groups be more useful for establishing a zero vs one large hot bore group?

Ehh. It doesn’t really matter that much. Just get 20’ish shots on a single aiming point and go from there.

The best thing for most would be to break and build the position for each shot, for those twenty rounds. The group will be larger, but will center you true cone.

 

[donrleonard]

As promised, here is a follow-up take on the initial cold/hot-bore test that kicked this thread off.

I've already demonstrated that I'm a mediocre shooter who's still learning ballistics. But I am a data nerd, and I was confused by some of the patterns I saw in those test results.

TL;DR: Looking back now, I see that only a few exhibited clear horizontal/vertical bias. The core of my confusion at this point relates to how the size of groupings (either no-flyers-allowed MOA, or the more forgiving mean radius) change between cold and hot bore for these rifles, and how POI shifts take place between the two as well.

I'll paste the targets and captions that I was curious about, along with some musings in italics below them, in hopes that it stimulates additional learning for all of us.



“Gun #1 no shift cold to hot.” “Well inside statistical variation.”

These look different to my eye. The cold bore group is nearly inside of one grid (half an inch?). The other is pushing out to nearly three grids. What measure of statistical variation is being used here as a guide?​

“Gun #2 no shift cold to hot:” “Well inside statistical variation.”

These look different to my eye also. The cold bore group is destroying the bullseye. The hot bore group, though certainly within minute of deer, looks to be opening up significantly and the mean POI drifting south. ​

“Gun #3 no shift cold to hot:” “Well inside statistical variation.”

I guess this is the one that seemed so strikingly different in terms of the way in which the “error” or POI is distributed. Same MOA, by the looks of it. But shots are walking horizontally when fired from a cold bore and vertically when hot.​

“Gun #5 no shift cold to hot.” “The rifle just doesn’t particularly like the ammo.”

I was puzzled by the post-hoc reasoning here. It’s not obvious to my eye that this rifle doesn’t like the ammunition. With the exception of one outlier in the first cold-bore test and another in the second hot one, it looks like a mighty fine rifle/ammo combo to me. Especially the second hot-bore grouping. While this rifle clearly experiences a shift in POI right and downward when fired from a hot barrel, the overall performance here sure does cast doubt on the cold bore theory--at least for this rifle. ​

"Gun #6 no shift cold to hot:” “Well inside statistical variation.”

At first glance I would tend to agree with this assessment. The POI doesn’t appear to shift all that much between a cold and hot barrel. But in a world where the word “flyer” isn’t allowed, the hot barrel very obviously is producing a degraded level of accuracy out of the hot barrel with those two shots that went astray. Again, I find myself wondering what statistical measure is being used to determine whether this was ‘inside statistical variation’?​

“Gun #7 no shift cold to hot:” “The rifle does not shoot this ammo well.”

Again, very different groupings and mean POIs, as well as more post-hoc reasoning. How could we reasonably know it was the ammo and not the hot bore producing the less-impressive hot-bore results?​

“Gun #8 no shift cold to hot:”

No qualms here. Just a desperate plea for Form to sell me this rifle. ​

Garbage barrels are garbage barrels. Barrels that walk, shift or move based on temperature are garbage.

True by definition. But a fundamentally different claim than one that bore temps don’t matter. If the central argument here is that bore temperature affects all rifles differently, I could more easily understand these results. My (amateur) read is that:

• Some rifles exhibit a small but non-trivial POI shift as the barrels heat up.
• Some rifles exhibit a larger mean radius when barrels heat up.
• Some rifles exhibit both.
• Some rifles exhibit none of the above.
• I should've bought a Tikka.

The data scientist in me would also be willing to consider another post-hoc rationalization: Did variation in shooters or rests over the course of these tests produce some of these shifts that I observed in the original test targets? Hard to prove, and I suppose these would be expected to be relatively constant across the cold- and hot-bore shots. Unless we start talking about shooter fatigue...





Moving on to my own cold/hot-bore results, a couple of reflections:

First, thank you so damn much. To you @Formidilosus and @Macintosh , for responding to my humble test and taking the time to plot my mediocre shooting out and help me think through how to zero my rifle based on these data. And to @NSI for sending me an incredibly thoughtful message about how I might begin to improve upon my field marksmanship. Rokslide has been an invaluable resource for me over the last two years as I sought to turn my childhood dream of going hunting into a healthy outlet for my mid-life crisis. But this kind of support? Really gents, I’m deeply grateful.

Overall I found the overlays insanely helpful. Indeed, I adjusted my rifle zeroing based on them. But I did have some confusion, mainly focused around the idea that the shot-by-shot variation that we observe would be expected to assume some cone-like normal distribution as @Macintosh described above. Specifically, Form's comment,

Here’s all 30 shots overlaid. There is no “pattern” to first shots. Draw a circle around all 30 shots and if you kept shooting, that circle would fill in.

Again, correct me if I’m mistaken here, but when I look at this shot pattern I don’t see the makings of a cone that is going to be filled in. I see a vertical string of cold-bore shots with a rightward POI shift, and a horizontal string of hot bore shots that is roughly centered on the target but with an upward POI bias.

Please feel free to put a Lil-Rokslider in his place here. And thanks again, all, for an incredibly informative exchange here.

 

[Marbles]

Statistically significant is key. I've not ran the numbers, don't know how they determine statistical significance, but if differences do not meet statistical significance in any data pool (and smaller samples need larger differences), then looking for patterns in them is nothing more than the data equivalent of fun house mirrors.

10 shots is a very small sample from a statistics perspective.

Now, if somebody can take the time to crunch numbers and give us some p values.

 

[Formidilosus]

As promised, here is a follow-up take on the initial cold/hot-bore test that kicked this thread off.

I've already demonstrated that I'm a mediocre shooter who's still learning ballistics. But I am a data nerd, and I was confused by some of the patterns I saw in those test results.

TL;DR: Looking back now, I see that only a few exhibited clear horizontal/vertical bias. The core of my confusion at this point relates to how the size of groupings (either no-flyers-allowed MOA, or the more forgiving mean radius) change between cold and hot bore for these rifles, and how POI shifts take place between the two as well.

I'll paste the targets and captions that I was curious about, along with some musings in italics below them, in hopes that it stimulates additional learning for all of us.



“Gun #1 no shift cold to hot.” “Well inside statistical variation.”
View attachment 780660

These look different to my eye. The cold bore group is nearly inside of one grid (half an inch?). The other is pushing out to nearly three grids. What measure of statistical variation is being used here as a guide?​

“Gun #2 no shift cold to hot:” “Well inside statistical variation.”
View attachment 780661

These look different to my eye also. The cold bore group is destroying the bullseye. The hot bore group, though certainly within minute of deer, looks to be opening up significantly and the mean POI drifting south. ​

“Gun #3 no shift cold to hot:” “Well inside statistical variation.”
View attachment 780662

I guess this is the one that seemed so strikingly different in terms of the way in which the “error” or POI is distributed. Same MOA, by the looks of it. But shots are walking horizontally when fired from a cold bore and vertically when hot.​

“Gun #5 no shift cold to hot.” “The rifle just doesn’t particularly like the ammo.”
View attachment 780663

I was puzzled by the post-hoc reasoning here. It’s not obvious to my eye that this rifle doesn’t like the ammunition. With the exception of one outlier in the first cold-bore test and another in the second hot one, it looks like a mighty fine rifle/ammo combo to me. Especially the second hot-bore grouping. While this rifle clearly experiences a shift in POI right and downward when fired from a hot barrel, the overall performance here sure does cast doubt on the cold bore theory--at least for this rifle. ​

"Gun #6 no shift cold to hot:” “Well inside statistical variation.”
View attachment 780664

At first glance I would tend to agree with this assessment. The POI doesn’t appear to shift all that much between a cold and hot barrel. But in a world where the word “flyer” isn’t allowed, the hot barrel very obviously is producing a degraded level of accuracy out of the hot barrel with those two shots that went astray. Again, I find myself wondering what statistical measure is being used to determine whether this was ‘inside statistical variation’?​

“Gun #7 no shift cold to hot:” “The rifle does not shoot this ammo well.”
View attachment 780665

Again, very different groupings and mean POIs, as well as more post-hoc reasoning. How could we reasonably know it was the ammo and not the hot bore producing the less-impressive hot-bore results?​

“Gun #8 no shift cold to hot:”
View attachment 780666

No qualms here. Just a desperate plea for Form to sell me this rifle. ​

True by definition. But a fundamentally different claim than one that bore temps don’t matter. If the central argument here is that bore temperature affects all rifles differently, I could more easily understand these results. My (amateur) read is that:

• Some rifles exhibit a small but non-trivial POI shift as the barrels heat up.
• Some rifles exhibit a larger mean radius when barrels heat up.
• Some rifles exhibit both.
• Some rifles exhibit none of the above.
• I should've bought a Tikka.

The data scientist in me would also be willing to consider another post-hoc rationalization: Did variation in shooters or rests over the course of these tests produce some of these shifts that I observed in the original test targets? Hard to prove, and I suppose these would be expected to be relatively constant across the cold- and hot-bore shots. Unless we start talking about shooter fatigue..

Do understand what was being tested?

Moving on to my own cold/hot-bore results, a couple of reflections:

First, thank you so damn much. To you @Formidilosus and @Macintosh , for responding to my humble test and taking the time to plot my mediocre shooting out and help me think through how to zero my rifle based on these data. And to @NSI for sending me an incredibly thoughtful message about how I might begin to improve upon my field marksmanship. Rokslide has been an invaluable resource for me over the last two years as I sought to turn my childhood dream of going hunting into a healthy outlet for my mid-life crisis. But this kind of support? Really gents, I’m deeply grateful.

Overall I found the overlays insanely helpful. Indeed, I adjusted my rifle zeroing based on them. But I did have some confusion, mainly focused around the idea that the shot-by-shot variation that we observe would be expected to assume some cone-like normal distribution as @Macintosh described above. Specifically, Form's comment,





Again, correct me if I’m mistaken here, but when I look at this shot pattern I don’t see the makings of a cone that is going to be filled in. I see a vertical string of cold-bore shots with a rightward POI shift, and a horizontal string of hot bore shots that is roughly centered on the target but with an upward POI bias.

Please feel free to put a Lil-Rokslider in his place here. And thanks again, all, for an incredibly informative exchange here.

You’re seeing what you want to see. Sometimes shots land in a line left to right. Sometimes up and down. Sometimes diagonally. Sometimes in a clockwise circle, sometimes counter clockwise. Sometimes in a star pattern. Etc, etc.


Shoot enough and you get something that looks like this-

Horizontal stringing, right?



Until you fire more shots-




Horizontal stringing again, right?




Again, until more are fired-




Of course, group size can make it easier or harder to see the cone-






The reason that the “cone” nature is easier to see in the last two is because the cone itself is so much smaller- it takes less rounds to fill out. Had the top two combos been fired for another 50 to 100 rounds, they too would have had a very visually round cone.

 

[Formidilosus]

Statistically significant is key. I've not ran the numbers, don't know how they determine statistical significance, but if differences do not meet statistical significance in any data pool (and smaller samples need larger differences), then looking for patterns in them is nothing more than the data equivalent of fun house mirrors.

10 shots is a very small sample from a statistics perspective.

Now, if somebody can take the time to crunch numbers and give us some p values.

10 shots is a small sample size. However, somewhere in this he and others either didn’t understand what was being looked at, or forgot it. It wasn’t group size.