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Effect of Temperature in Power Factor/Reloading/Chrono


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Friends,

 

Its getting cold and colder here in GTA Canada. I am also new in reloading with the use of chrono as well. I have findings:

1. In fall season, the PF reading in my CED M2 chrono was higher than this winter, eventhough that the indoor range has heater. With same load specs (primer, powder qty, AOL, crimp).

2. The PF readings were inconsistent (I made sure that all loads are equal in regards to specs)

 

Questions:

1. What is the percentage effect of surrounding temperature/weather to gun powder (I am using Titegroup for my minors and HS6 for Majors)?

2. Are there tables of this variations out there?

3. Right now, if I got 126 to 129 pf in my minors, Is it right to assume that this will be higher during summer season? I am planning to stock up 9mm minor loads for summer Level 3.

 

Hoping for all your assistance.

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Not always higher in warm weather. Some powders are what we call reverse temp sensitive. Meaning the PF goes up as it gets colder. Best suggestion is just search here for powder temperature sensitivity etc for all the postings we have made over the years

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Indoor chrono can be tricky because of the lighting. flickering flourescents shadows , etc. depending on your chrono.  When you said you

1 hour ago, Orbit said:

PF readings were inconsistent

Did you mean from session to session or in that one session ?
If I'm not looking at single digit SD I'm gonna change something. Too much or too little powder can do that. You may have to up your charge a bit or maybe shorten OAL or go to a heavier bullet.  I think you will find most of us load 5 or so over floor... 130-132 for minor, 170-173 major. Really those few extra FPS arnt gonna effect your score at all, but a few fps under sure can.
Ive never seen much of a difference when I chrono my loads and my major match chrono results tend to be pretty close to my home results.
I use tightgroup and WST. 
I do have to say though I am a fair weather shooter. Usually doing my chrono work on nice days,, and matches I shot tend to be in summer.

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50 minutes ago, Sarge said:

Not always higher in warm weather. Some powders are what we call reverse temp sensitive. Meaning the PF goes up as it gets colder. Best suggestion is just search here for powder temperature sensitivity etc for all the postings we have made over the years

 

Thanks, I will search fo that

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15 minutes ago, Joe4d said:

Indoor chrono can be tricky because of the lighting. flickering flourescents shadows , etc. depending on your chrono.  When you said you

Did you mean from session to session or in that one session ?
If I'm not looking at single digit SD I'm gonna change something. Too much or too little powder can do that. You may have to up your charge a bit or maybe shorten OAL or go to a heavier bullet.  I think you will find most of us load 5 or so over floor... 130-132 for minor, 170-173 major. Really those few extra FPS arnt gonna effect your score at all, but a few fps under sure can.
Ive never seen much of a difference when I chrono my loads and my major match chrono results tend to be pretty close to my home results.
I use tightgroup and WST. 
I do have to say though I am a fair weather shooter. Usually doing my chrono work on nice days,, and matches I shot tend to be in summer.

Hi Joe,

 

I am using same specs for my minor reloads but you maybe right and have a point of double checking my OAL and exact quantity of powder. My best example was I chronoed the following:

1.12" 3g TG .378 crimp 21 deg for 131pf, after a while repeat the process and went down to 128 pf. In my recollection, most probably the temp changed to 19 deg inside the indoor range. I am using a CED M2 chrono with infra red sensors.

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20 minutes ago, jwhittin said:

"The PF readings were inconsistent (I made sure that all loads are equal in regards to specs)"

How are you measuring your average velocity? How many rounds and what is the Standard Deviation?

 

Hi,

 

I am using CED M2 chrono. Average of 3 shots and used the built in program for the average pf.

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That's the reason your results are not consistent.  With only 3 rounds there is a high statistical uncertainty in the measurements.  Use 8 rounds and know your standard deviation (STD).  Add 2 to 3 times your standard deviation to the minimum required velocity to make PF. That is your desired average load velocity. That gives you a high degree of confidence of passing PF.  

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1 hour ago, jwhittin said:

That's the reason your results are not consistent.  With only 3 rounds there is a high statistical uncertainty in the measurements.  Use 8 rounds and know your standard deviation (STD).  Add 2 to 3 times your standard deviation to the minimum required velocity to make PF. That is your desired average load velocity. That gives you a high degree of confidence of passing PF.  

 

I will do that. What is your standard deviations for 9mm minor and major for my comparison purposes if you may?

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I don't shoot 9mm but people I've spoken to are typically in the 8 to 12 fps range.  It depends on your components, equipment, and your reloading process and any changes in any of those areas can change your STD.   For 40 Maj, my STD is about 15 to 20 fps. I've used the same load, components, and press/process for several years so I haven't see much change.

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1 hour ago, Joe4d said:

I use at least 10 rounds and chrono and load on different days with same press settings before I go into mass production.. 

 

Thank you. I will take your advice for this chrono process.

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20 minutes ago, jwhittin said:

I don't shoot 9mm but people I've spoken to are typically in the 8 to 12 fps range.  It depends on your components, equipment, and your reloading process and any changes in any of those areas can change your STD.   For 40 Maj, my STD is about 15 to 20 fps. I've used the same load, components, and press/process for several years so I haven't see much change.

 

I will use your std of 12 fps. I didn't know about this. Next chrono i will observe and record all. Thnks

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34 minutes ago, Orbit said:

Guys, just to ask again....Is weather or room temperature affects the outcome of chrono? PF?

Again, yes.

  This is why some folks don’t load 15k rounds to shoot all year. In the spring around here it can be 40 in the morning and 75 by the last stage. Then got all summer. Then fall hits and it can be 40 all day. You get the picture.

  We also tend to either do a lot of load development or use powders that fluctuate very little or both.

  Also why trying to load to 126 or 166 PF is dumb. 

Edited by Sarge
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1 hour ago, Sarge said:

Again, yes.

  This is why some folks don’t load 15k rounds to shoot all year. In the spring around here it can be 40 in the morning and 75 by the last stage. Then got all summer. Then fall hits and it can be 40 all day. You get the picture.

  We also tend to either do a lot of load development or use powders that fluctuate very little or both.

  Also why trying to load to 126 or 166 PF is dumb. 

 

Hi, what do you think the best 9mm minor powder that is least to be affected by weather or temp. Here in GTA Canada, weather is fluctuating even in summer

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4 hours ago, Orbit said:

 

Hi, what do you think the best 9mm minor powder that is least to be affected by weather or temp. Here in GTA Canada, weather is fluctuating even in summer

N320

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I don't chrono since we shoot steel challenge with no PF minimum, but here's an interesting observation regarding N320 which might apply to other powders:

 

My wife's load is 3.7gr N320/115gr Acme.  This is the softest load that will reliably cycle her 9mm 1911.  In the past I've seen temperature sensitivity even in our mild winters and have had to bump up the load, but with the Dillon at the same powder micrometer setting I'm getting a slightly heavier drop, maybe 0.1gr more.  The gun continues to cycle and, thanks to the combination of 1050 and Mark 7, the ejection is very, very consistent.  So my loading in early am 40 degree temperatures seem to auto-correct for the powder temperature sensitivity - go figure.

 

Are you loading in an unheated (probably not) or at least a cold room?  Are the drops the same weight or the same micrometer setting?  Just something to think about.

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  • 4 weeks later...

When I shot in a winter trap league, we used to leave the boxes of shotgun shells on the dashboard of the car in the sun to keep them warm and grab them when it was time to shoot. Was only 2 boxes so it wasn't a big deal. People who left their stuff out in the cold waiting (couple hours sometimes) always seemed to have the occasional squib or noticeably weak shell. Now, everybody reloaded at the time and it could have been just a short powder charge, but we still tried to keep the shells warm to a point. 

 

I guess what I'm saying is don't shoot cold rounds over the chrono unless you just want to see what happens, and I sure wouldn't be giving any cold rounds to be tested before a match. 

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I tested some rounds that were at room temperature then tested the same load after getting them pretty warm in a jar in the sun.  I noticed zero difference with the labradar.  These were with WST which people say is inverse temperature sensor.

 

I would bet that the difference in lighting on those two days played more of a part in your perceived difference than the temperature unless you were using a chrono coffin.

 

What kind of lighting is on your indoor range and do you have any sort of auxiliary lighting on your chrono?

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