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

[atmat]

What cartridge are you shooting that gets 20k rounds through the same barrel?

#8 and #10 are both my rifles. #8 has more than 20,000 rounds on it without ever being cleaned; and #10 is a 6XC with +/- 700 rounds on it without ever being cleaned.

8). Tikka T3 Lite 223, suppressed, with SWFA fixed 6x scope. UM ammo.

 

[Formidilosus]

What cartridge are you shooting that gets 20k rounds through the same barrel?

That one is a 223. At around 14,000 rounds it had opened up to about 1.4 MOA for ten round groups. The barrel was cut back a bit, threaded for a suppressor, and went back to 1’ish MOA for ten. It has stayed that way since.

I am not saying that one should expect that with all, however that one has. There are Roksliders that have shot that rifle for about 5,000 rounds themselves.

 

[JGRaider]

That's amazing, thanks.

 

[dirtytough]

Why are only 2 of the rifles actually zeroed?

 

[Formidilosus]

Why are only 2 of the rifles actually zeroed?

Because for this it has no bearing on the results.

 

[dirtytough]

Because for this it has no bearing on the results.

Wow I would have never guessed. Thanks for the education.

 

[Formidilosus]

Wow I would have never guessed. Thanks for the education.

I am not sure if you are legitimately asking or if you are just trolling.
However, whether a rifle is zeroed or not, has no bearing on point of impact changes from cold to hot. It can be “zeroed” two feet to the left of point of aim, and measure the deviation between cold barrel and hot barrel groups.

 

[hdc77]

This has been an eye opener for me, now I’m depressed because I’m gonna have to stop blaming the hot barrel for me sucking at shooting. Thanks for putting the time and effort. Also, the ballistic podcast with Shoot2Hunt was fire.

 

[dirtytough]

I am not sure if you are legitimately asking or if you are just trolling.

It was sarcasm.

Your response of “because it doesn’t matter for this test” didn’t answer the question. Your response was as pointless of a post as my sarcastic post you just responded to.

I’ll quit wasting your time.

 

[SDHNTR]

I didn’t read the whole thread so forgive me if this has already been addressed…. But I have two questions/comments specific to the test and a random unrelated question …

True, I don’t see any meaningful poi shift in group center from cold to hot, but I do see a sizeable increase in overall group size, at least with a few of those rifles. Which to me may mean that if one of your shots falls on the outside of that increased cone due to heat, that may result in a miss versus a hit. Right? Tell me what I’m missing.

Also, what exactly determined hot and cold? I know if I rip off 10 consecutive shots out of my 7mag (only mentioning that cartridge as being somewhat comparable to the 7prc used here) without waiting in between, shots 6 or 7 thru 10 are gonna be out of a pretty hot barrel. Yet those would be deemed out of the “cold” group because it was still shots 1-10? Then what shot numbers were the “hot” barrel and was this process the same across the various rifles to determine what was hot and what was cold? Or was it just something subjective like feeling the barrel?

Oh, and gun #8’s groups are especially impressive with a 6x scope. Do you have really good eyesight? Personally, I can take the same gun/load and shoot a way better group with say 15 or 16x+ than I can at 9-10x or less, for example. I can just simply see and hold on the spot better. 6x, forget it. I would really be struggling. No problem on game or steel gongs, but man I can’t hold tight on a small paper bullseye for Jack without some magnification. Is that just me and my eyes? Or is there some technique I should be using to shoot tighter groups on paper with lower mag scopes?

 

[HighUintas]

A few things:

What about the dwell time of the cartridge in the chamber and the temp effect on powder? Some folks may sit a long time getting settled, let the cartridge heat up a lot, and then assume it was because the barrel was warm or hot.

What about statistical precision for the shooter/rifle system between the cold shots and the hot shots? Where's the proof that the precision is the same between the two even though you're ripping 10 shots off very quickly?

As sdhntr mentioned, the group mean radius is much different between cold and hot... This is evidence that something is different in the system.

You can't definitively state that these barrels don't shift when hot with this test when your limits (1mil) for determining if a shift happened are within the statistical uncertainty of the control. You're just showing that a shift due to hot barrels can't be detected due to the noise of your shooter/rifle system.

 

[Formidilosus]

I didn’t read the whole thread so forgive me if this has already been addressed…. But I have two questions/comments specific to the test and a random unrelated question …

True, I don’t see any meaningful poi shift in group center from cold to hot, but I do see a sizeable increase in overall group size, at least with a few of those rifles. Which to me may mean that if one of your shots falls on the outside of that increased cone due to heat, that may result in a miss versus a hit. Right? Tell me what I’m missing.

Firstly, there is an increase or decrease in groups size due to random variations in expected groups with no changes. A rifle that averages 1 MOA for ten round groups, will shoot some ten round groups at .6-.7 MOA, and some at 1.4’ish moa. Secondly, and mostly what was seen with a couple of the rifles is barrel mirage. Some of the rifles when shot for 10 rounds straight were producing horrible mirage by shot 6-7. The barrels were being fanned to keep it under control.

Also, what exactly determined hot and cold? I know if I rip off 10 consecutive shots out of my 7mag (only mentioning that cartridge as being somewhat comparable to the 7prc used here) without waiting in between, shots 6 or 7 thru 10 are gonna be out of a pretty hot barrel. Yet those would be deemed out of the “cold” group because it was still shots 1-10?

I’m not following you what you are saying/asking here. The cold groups were ten individual cold shots with the barrel returning to ambient temperature between shots. The “hot” barrel groups are shots 1-10 quickly- 30-45 seconds on average from start to finish. One or two rifles there was a few second pause in the middle because barrel mirage made aiming near impossible.

Then what shot numbers were the “hot” barrel and was this process the same across the various rifles to determine what was hot and what was cold? Or was it just something subjective like feeling the barrel?

? It was explained in the OP.

Oh, and gun #8’s groups are especially impressive with a 6x scope. Do you have really good eyesight? Personally, I can take the same gun/load and shoot a way better group with say 15 or 16x+ than I can at 9-10x or less, for example. I can just simply see and hold on the spot better. 6x, forget it. I would really be struggling. No problem on game or steel gongs, but man I can’t hold tight on a small paper bullseye for Jack without some magnification. Is that just me and my eyes? Or is there some technique I should be using to shoot tighter groups on paper with lower mag scopes?

I do have good eyesight, but that isn’t why the groups are good. Magnification is mostly a visual comfort thing, not an “ability” thing. Reticle thickness plays a part, however if you can quarter a target, it functionally doesn’t matter what magnification is used. Really thick reticles that usually one in lower mag scopes do hinder group shooting to an extent, though it also depends on what type of reticle (center dots versus duplex, etc).

People aren’t comfortable with lower magnification, once people use lower magnification enough they stop caring about it.

 

[Formidilosus]

A few things:

What about the dwell time of the cartridge in the chamber and the temp effect on powder? Some folks may sit a long time getting settled, let the cartridge heat up a lot, and then assume it was because the barrel was warm or hot.

What about it? Are you asking if it’s a thing?

What about statistical precision for the shooter/rifle system between the cold shots and the hot shots? Where's the proof that the precision is the same between the two even though you're ripping 10 shots off very quickly?

What are you asking- this wasn’t about precision, it was about whether “cold bore shots” landing in a different location is a thing with properly built rifles.

As sdhntr mentioned, the group mean radius is much different between cold and hot... This is evidence that something is different in the system.

Again, we didn’t care about precision- that wasn’t what was being looked at. What was being “tested” was point of impact changes between “cold bore shots” and hot bore shots. “Do good barrels/rifles walk or change point of impact relative to point of aim as they heat up?” The answer was, and is “no”.

POI or groups can change a bit due to barrel mirage, but with properly stress relieved barrels and properly assembled rifles, barrel heat isn’t causing groups to open up nor groups to shift.

You can't definitively state that these barrels don't shift when hot with this test when your limits (1mil) for determining if a shift happened are within the statistical uncertainty of the control.

I’m not trying to be rude, did you read the original posts? It wasn’t 1 mil shifts, it was .1mil- one click on most scopes, and well inside standard expected variability of of the vast majority of barrels/rifles, and what is functionally usable.

You're just showing that a shift due to hot barrels can't be detected due to the noise of your shooter/rifle system.

That was the point of the event.

 

[Marbles]

You can't definitively state that these barrels don't shift when hot with this test when your limits (1mil) for determining if a shift happened are within the statistical uncertainty of the control. You're just showing that a shift due to hot barrels can't be detected due to the noise of your shooter/rifle system.

Definitive is a very high ask and not really a concept in statistics or science.

What about statistical precision for the shooter/rifle system between the cold shots and the hot shots? Where's the proof that the precision is the same between the two even though you're ripping 10 shots off very quickly?

As sdhntr mentioned, the group mean radius is much different between cold and hot... This is evidence that something is different in the system.

They designed a test with pre agreed measurements and outcomes. Within the design of that test there was not a shift. The weakness of that design were accepted beforehand. It is an appropriate application of good trial design.

Post hoc combing of data is hypothesis generating, but a skeptical eye should be given to attributing scientific validity to it. I.e. noting the change in group size can be a hypothesis for future testing, but anything beyond that is a scientifically questionable conclusion. This is especially true here as round counts are too low to give data on precision and the test was not designed to evaluate precision.

 

[Formidilosus]

The genesis of this is the ever revolving discussion that people need to be shooting larger shot group sizes to determine actual probability of group sizes, and the true center of their cone, generally met by the- “I can’t shoot more than three shots in a row while zeroing because the zero starts moving” or “my groups open up after 3 shots” nonsense.

If the targets are looked at, and especially when the video comes out, it is obvious why zeroing based on a 3-5 shot group, or a couple of 3-5 shot groups, can and will cause errors in zero that can be functionally observed and accounted for. The vast majority of rifle systems can and will have .5 up to 1 MOA shifts in center between 3-5 shot groups with no changes. However most rifles do not show a large enough variability between 10-20 round groups to show a shift that can be adjusted out.
Properly built rifles shoot inside their true cone regardless of cold or hot barrel. That cone- regardless of any external factors- is way larger (statistically speaking) than a few 3 or 5 shot groups. Even a 10 shot group has variability. There is a point when a level of precision is reached that variability does not have a practical meaning.
As a functional, practical matter- if a rifle varies in center of 10 round groups by .1 MOA (1/10th MOA) from group to group from the true mean point of impact, it doesn’t matter- you can’t adjust a tenth MOA out. With that system a single 10 round group shows you the center of the cone- to less than a single click of the scope. If however from one group to the next, the center varies by .5 MOA or even 1 MOA- that matters and can be adjusted out. When that is the case (nearly all field rifles are these, btw) it requires more than ten rounds to see the true center. By 20 rounds- whether those are 20 straight shots, or multiple groups to get 20 shots on one target, the mean point of impact will not materially change for the vast majority of rifle systems.


All of this equals- shoot more rounds and have less error in zero location, and a much more realistic understanding of the “precision” of each rifle.

 

[Formidilosus]

Definitive is a very high ask and not really a concept in statistics or science.


They designed a test with pre agreed measurements and outcomes. Within the design of that test there was not a shift. The weakness of that design were accepted beforehand. It is an appropriate application of good trial design.

Post hoc combing of data is hypothesis generating, but a skeptical eye should be given to attributing scientific validity to it. I.e. noting the change in group size can be a hypothesis for future testing, but anything beyond that is a scientifically questionable conclusion. This is especially true here as round counts are too low to give data on precision and the test was not designed to evaluate precision.

Correct. Thank you.

 

[The Guide]

Why are only 2 of the rifles actually zeroed?

Have you ever shot groups with a rifle that is zeroed and accurate? You shoot your aim point out and the remaining shots become increasingly difficult to maintain the same point of aim. I don't even worry about adjusting my zero until after I've shot all the groups I want. Last thing I do is adjusting the final zero and verify. Zeroing has nothing to do with groups and can be detrimental to group size.

Jay

 

[HighUintas]

Definitive is a very high ask and not really a concept in statistics or science.


They designed a test with pre agreed measurements and outcomes. Within the design of that test there was not a shift. The weakness of that design were accepted beforehand. It is an appropriate application of good trial design.

Post hoc combing of data is hypothesis generating, but a skeptical eye should be given to attributing scientific validity to it. I.e. noting the change in group size can be a hypothesis for future testing, but anything beyond that is a scientifically questionable conclusion. This is especially true here as round counts are too low to give data on precision and the test was not designed to evaluate precision.

How is definitive not a concept in statistics or science? A definitive statement is a final conclusion with seemingly high authority or confidence. Aside from whether or not it's a "concept"? in science, the statements that have been made in this thread due to the testing are definitive. It would have been better stated that quality rifle barrels properly relieved of stress do not shift due to heat an amount that would induce larger variability within the shooter's system.

The point being made on the precision of the cold vs hot group, is that there was no validation shown of the mean POI for either method of shooting. A shooter shooting 10 cold shots may be different than a shooter ripping off 10 straight very quickly. Noticing there could be a difference in the mean radius between the two groups and considering what was just stated, a statement as definitive as was made can't be relied on. A TMV of sorts would make the results a lot stronger.

I'm not saying it was a poor test. Quite the opposite. It's very useful and absolutely shows that a shooter, even a very competent one, isn't going to notice a shift from heat. I'm just pointing out that not being accurate enough with conclusionary statements, especially when not considering all variables or having small sample sizes like 10 rounds, could lead people to come to the wrong conclusion themselves.

 

[Boonie327]

Some of you guys are over thinking this wayyyy too much. The simple fact that he’s dealing with mirage eliminates any “definitive” results within a statistical method as defined by pointy heads. He clearly illustrates his objective, which is to show that all the guys complaining about “hot” barrels affecting POI and groups are full of crap unless they’re shooting junk barrels. At some point, he’s going to say “WTF” when dealing with this crap and stop wasting time and money on providing useful information. Let’s be honest, where else are you going to get real world useful information that relates to the way most of us shoot other than on this forum?

 

[SDHNTR]

Firstly, there is an increase or decrease in groups size due to random variations in expected groups with no changes. A rifle that averages 1 MOA for ten round groups, will shoot some ten round groups at .6-.7 MOA, and some at 1.4’ish moa. Secondly, and mostly what was seen with a couple of the rifles is barrel mirage. Some of the rifles when shot for 10 rounds straight were producing horrible mirage by shot 6-7. The barrels were being fanned to keep it under control.




I’m not following you what you are saying/asking here. The cold groups were ten individual cold shots with the barrel returning to ambient temperature between shots. The “hot” barrel groups are shots 1-10 quickly- 30-45 seconds on average from start to finish. One or two rifles there was a few second pause in the middle because barrel mirage made aiming near impossible.





? It was explained in the OP.






I do have good eyesight, but that isn’t why the groups are good. Magnification is mostly a visual comfort thing, not an “ability” thing. Reticle thickness plays a part, however if you can quarter a target, it functionally doesn’t matter what magnification is used. Really thick reticles that usually one in lower mag scopes do hinder group shooting to an extent, though it also depends on what type of reticle (center dots versus duplex, etc).

People aren’t comfortable with lower magnification, once people use lower magnification enough they stop caring about it.

Good explanations. Thanks. I understand what you are saying about natural and random variation in group sizes regardless of barrel temp, but is it not at least somewhat telling that the groups here do tend to consistently open up with heat? Yes, that could be mirage, but mirage is also a byproduct of heat. So it seems one could say that heat CAN (not necessarily WILL) open up groups, even if mirage is the true culprit. Mirage wouldn’t be there if not for the barrel heat. Which is then perhaps to say that when shooters state their groups often open up with heat, it’s not all “nonsense”? It can happen. It’s shown here.

I’m not trying to argue. I’m just trying to understand why what I’m seeing in these test results differs from what you’re saying.

I’ve owned exactly one rifle out of many dozen in my life that most certainly was effected by heat. A Weatherby Vanguard 25-06. After a few shots if not allowed to thoroughly cool, it absolutely would spray bullets all over the place.