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

[Marbles]

I'm terrible at cleaning barrels and probably have shot them too hot (for some people) when shooting prairie dogs. We have found some powders don't want to be in a hot chamber very long without building pressure in those loads.

For the advocates of "don't worry about a hot barrel", what attention are you taking to make sure the loads are temperature stable? Example, are Hodgdon Extreme powders or something similar being used. Or, are you just going to get it lit shortly after chambering a round? When we are dog shooting, we are going to keep the chamber open until ready to shoot to hopefully cool the barrel a little and keep the loads from getting too warm.

I only load temp stable single base powder. I don't care enough about velocity to try other options, but do care about reliability. I have seen velocity spikes with letting a round sit in a hot chamber, but not pressure sings with my loads. If a hot chamber caused pressure signs, I would drop my powder charge on that load as for reliability I don't want to be on the edge of over pressure.

 

[Shraggs]

Form, please keep in mind, there are new members in this community that don’t know you, and may take your advice based on your excessive post count.

You keep suggesting, “Pouring water on a Hot barrel, and Suppressor” - Bad advice, clearly.

You support getting a barrel smoking hot, despite your findings ‘point of impact stays the same’ (until of course the throat wears out, from it). It’s no wonder, Loctite don’t work on your guns, you abuse the hell out them. Fine, in the name of testing, or a zombie apocalypse, but recommended??? Maybe rotate in another gun, while one air cools, don’t you think?

Interesting conclusion, but not sure I agree.

My question was simple if I’m practicing ie shooting mirage impedes, me at least. I’m adding a gallon of water from now on in summer.

 

[Formidilosus]

For the advocates of "don't worry about a hot barrel"

Who has said don’t worry about hot barrels?

 

[Chris in TN]

No, 5-7 rounds does not get the above average rifle within a single click. 20 shots in a group does that.

If you took all the “my rifle is half MOA all day long” guns, and put them in a Wiseman return to battery fixture and shot them in a tunnel- the average 95% come would be 2 to 2.5 MOA.

I will freely admit that I am pushing my own boundaries of what I grasp of stats here - I took grad level stats in 2001, I think, and have used some of the material for work at times but don't use the harder parts on a regular basis. I've been using some number of shots greater than 3, usually greater than 5, often 10 or more, off and on, for a lot of years. But I haven't touched the harder parts of the underlying math in a lot of years. I've been running on the assumption that 5-7 shots was sufficient (at least in general - I'm not shooting hundreds of yards with my less accurate rifles) and this makes me revisit that assumption.

The bad news: I couldn't calculate the answer to the underlying question here by hand to save my life.
The good news: AI can. This is one of the first times I've used it for much of anything.

The best ten-shot group I can distinctly remember firing was roughly 0.9moa at 100 yards (probably why I remember it). It might have been 0.875ish. I'm confident it was under 0.9. It's been a while.

More typical for the better rifles I own, is more like 1moa, and 1.25 moa for more 'average' stuff. I'm ignoring the less-than-average stuff here because hopefully most of us aren't attempting our longest shots with our worst rifles. I certainly own rifles that would struggle to even make 3-4moa. But again, I'm not shooting them at great distances.

Those group sizes - 0.9moa to 1.25moa for ten shots - statistically, likely represent total cones of fire of ~1.75 to 2.5 moa. So I'm going to use those 1.75 to 2.5 moa figures. Those compare well with the 2 to 2.5 moa you refer to.

I asked Google Gemini to model the problem, using a 1.75moa, 2moa, and 2.5moa hypothetical rifle, and tell me how many shots, uh, samples, I needed, to be within 0.25 units (one 1/4moa click) of the true population mean, or zero.
I'm assuming a normal distribution (3SDs cover 99.7%). That's a huge assumption, and if I assumed a uniform distribution the sample sizes absolutely would increase greatly.

But Gemini is showing a need for 17 shots to be 95% at 2.5moa, 11 shots to be 95% at 2moa, and 9 shots to be 95% at 1.75 moa.

I will probably stick with 5-7 for the foreseeable future. Ammo costs money (and time, which sometimes is worth more than money), some degree of uncertainty is acceptable, and I'm monitoring with future zero checks at various intervals anyway. And, importantly, I have zero intentions of shooting at animals beyond 500 yards, and very rarely shoot steel past 600 or 750. If that changes I absolutely see your point that I need more shots for initial zeroes, so thank you for that.

‎Gemini - direct access to Google AI

Created with Gemini

gemini.google.com

Truth be told, I don’t know what I’m supposed to do. I’m in my mid 40’s and it’s our first. I’m probably doing it wrong.

I became a really good bullet caster when our babies were in the napping phase. On winter Saturdays during naptime I'd make a year's worth of pistol projectiles. Man, enjoy this time. It will not last.

 

[Formidilosus]

The best ten-shot group I can distinctly remember firing was roughly 0.9moa at 100 yards (probably why I remember it). It might have been 0.875ish. I'm confident it was under 0.9. It's been a while.

More typical for the better rifles I own, is more like 1moa, and 1.25 moa for more 'average' stuff.

1.25 moa consistently for ten rounds groups is quite good- very few guns and shooters are doing that.

I'm ignoring the less-than-average stuff here because hopefully most of us aren't attempting our longest shots with our worst rifles. I certainly own rifles that would struggle to even make 3-4moa. But again, I'm not shooting them at great distances.

Those group sizes - 0.9moa to 1.25moa for ten shots - statistically, likely represent total cones of fire of ~1.75 to 2.5 moa. So I'm going to use those 1.75 to 2.5 moa figures. Those compare well with the 2 to 2.5 moa you refer to.

I asked Google Gemini to model the problem, using a 1.75moa, 2moa, and 2.5moa hypothetical rifle, and tell me how many shots, uh, samples, I needed, to be within 0.25 units (one 1/4moa click) of the true population mean, or zero.
I'm assuming a normal distribution (3SDs cover 99.7%). That's a huge assumption, and if I assumed a uniform distribution the sample sizes absolutely would increase greatly.

But Gemini is showing a need for 17 shots to be 95% at 2.5moa, 11 shots to be 95% at 2moa, and 9 shots to be 95% at 1.75 moa.

I will probably stick with 5-7 for the foreseeable future. Ammo costs money (and time, which sometimes is worth more than money), some degree of uncertainty is acceptable, and I'm monitoring with future zero checks at various intervals anyway. And, importantly, I have zero intentions of shooting at animals beyond 500 yards, and very rarely shoot steel past 600 or 750. If that changes I absolutely see your point that I need more shots for initial zeroes, so thank you for that.

‎Gemini - direct access to Google AI

Created with Gemini

gemini.google.com

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Yes, that’s works out almost correct when taken in large data sets (lots and lots of groups fired and averaged)- it does not work out with a single 10 shot group. Live fire shows this easily.

From a true 1.5 MOA gun, a 5-7 shot group can have variance from true center of 1 MOA or so.

It is so much cheaper in the long run to just shoot 10 shots, adjust, shoot ten shots. 20 shots and you are done.

 

[Chris in TN]

1.25 moa consistently for ten rounds groups is quite good- very few guns and shooters are doing that.





Yes, that’s works out almost correct when taken in large data sets (lots and lots of groups fired and averaged)- it does not work out with a single 10 shot group. Live fire shows this easily.

From a true 1.5 MOA gun, a 5-7 shot group can have variance from true center of 1 MOA or so.

It is so much cheaper in the long run to just shoot 10 shots, adjust, shoot ten shots. 20 shots and you are done.

Thank you. I absolutely do see your point. I also hadn't thought about splitting that into 10/adjust/10, which also makes it a bit more palatable. Thanks again. I'm still learning.

 

[Shraggs]

When Form first introduced these concepts I gravitated to QC protocol in manufacturing from my past. If an n = 1000 (in this case I believe he has said the fbi remote gun will show true cone of fire in 1000). He has stated and the hornady podcast that 30 gets you a 95% confidence of a 1000.

If I recall, 10 is more 75% ish predictive of the 1000. At least that’s how I’ve come to grips with it.

Consistent 10 groups if adequate accuracy is more than enough for general hunting purposes. Especially if repeatable in real hunting positions.

 

[journeyman713]

I think I actually shoot and know what happens, and you guess.

From your personal experience, what happens when you pour water on a barrel to cool it off?

As the self appointed expert on all thing guns, please tell us what happens when you pour water on a smoking hot barrel, and suppressor. It was the original question after all.

 

[Harvey_NW]

As the self appointed expert on all thing guns, please tell us what happens when you pour water on a smoking hot barrel, and suppressor. It was the original question after all.

Do you know how hot steel has to be for a quench to affect it, and that most of the context is referring to shot strings from bolt rifles?

 

[Marbles]

As the self appointed expert on all thing guns, please tell us what happens when you pour water on a smoking hot barrel, and suppressor. It was the original question after all.

He has already said it is fine so long as things are not glowing, aka nothing concerning happens.

You then said it was a bad idea. The burden is on you as to why as per basic logic @Formidilosus has already answered the question. My guess, is it is your "common sense" and you have no leg to stand on when more than oracular statements are needed.

 

[journeyman713]

He has already said it is fine so long as things are not glowing, aka nothing concerning happens.

You then said it was a bad idea. The burden is on you as to why as per basic logic @Formidilosus has already answered the question. My guess, is it is your "common sense" and you have no leg to stand on when more than oracular statements are needed.

Take it easy Mable, you already pointed out your phobia to common sense. I can respect that, I have an allergy to stupidness, tend to breakout with commonsense. Maybe stay in your lane, there’s not much commonsense in your fanboy club, you should be good there.

Besides, Form can answer for himself, 13,850 posts don’t lie. He’s advocating pouring water on some expensive equipment. Some people might confuse that with complete ignorance. Just hoping it clears it up for us. I’m pulling for him.