Temperature and bullet velocity

[abb1]

Okay, this kind of blew me away today.  I have always loaded 9mm major using 6.9 gr of WAC using a 124 FMJ at 1.15". I tested my rounds using a Caldwell G2 Chrono lasMarch indoors at 19C (66F) and a 10 group string averaged 1377 fps or a PF of 170. Today I had my ammo sitting in the sun (just where it was put), and it was 30C outside in the sun (87F). I decided to  chrono my ammo again (using the same chrono) for an upcoming match and an average of 10 rds chronoed at 1557 average or 193 PF. Can the temperature make the ammo go almost 180 FPS faster??? There were no real signs of pressure. Has anyone else noticed that big of a velocity change shooting in hot temperatures? This does not seem right......

Edited July 13, 2017 by abb1

[wrench459]

While hunting in the great white north.

I did notice a marked slow down of the bullets.

Burrrrrr

[Sarge]

1 hour ago, abb1 said:

Okay, this kind of blew me away today.  I have always loaded 9mm major using 6.9 gr of WAC using a 124 FMJ at 1.15". I tested my rounds using a Caldwell G2 Chrono lasMarch indoors at 19C (66F) and a 10 group string averaged 1377 fps or a PF of 170. Today I had my ammo sitting in the sun (just where it was put), and it was 30C outside in the sun (87F). I decided to  chrono my ammo again (using the same chrono) for an upcoming match and an average of 10 rds chronoed at 1557 average or 193 PF. Can the temperature make the ammo go almost 180 FPS faster??? There were no real signs of pressure. Has anyone else noticed that big of a velocity change shooting in hot temperatures? This does not seem right......

That's too much swing for autocomp in my experience. Something else seems to be at play here.

 My load is 7.4 WAC with 121's @ 1.165. In 75 degree weather they chrono'd at 173 and change at two matches. A few weeks later when it was 85 degrees and humid as heck it jumped to just over 175. That's within margins of error for chronoes so it MIGHT have been affected by the heat a little.

[lefty o]

extremes in heat and cold can greatly affect velocity. some powders are more sensitive to temps than others.

[Hi-Power Jack]

Have to agree with Sarge.

 

I also use WAC and 124 gr JHP's, and I would NOT expect such marked swings

from 20 F to 95 F, much less from 66 F to 87 F.

 

Much too large a fluctuation.

 

I'd also expect to see some signs of pressure at PF 193.

 

Since your reading the first time seems about right, I'd suspect the 2nd reading.

 

Probably a smaller point, I usually fire 20 rounds over the chrono to get an average -

a higher sample size might help a little. 

 

But, as Sarge mentioned, something else

interfered (sunlight, the way you set up the chrono, the distance fired (muzzle

blast on the screens), etc etc.

 

Where in Canada are you?   I used to live in Toronto, Cornwall, Saskatoon

and Edmonton, over the years.

[Shmella]

Has anyone above left ammo in the sun on a 80-90degree day and then chrono???? It is mentioned that you guys have chronoed ammo in hot weather, but ammo left in the sun would be simulating something like (wild guess) 140degree+ temperatures. I have wondered the same thing myself as the OP. There has been many times where my range bag/ammo or mags have been left on a table at a match in the sun and I questioned the pf swinging due to it.

Edited July 13, 2017 by Shmella

[abb1]

4 hours ago, Hi-Power Jack said:

Have to agree with Sarge.

 

I also use WAC and 124 gr JHP's, and I would NOT expect such marked swings

from 20 F to 95 F, much less from 66 F to 87 F.

 

Much too large a fluctuation.

 

I'd also expect to see some signs of pressure at PF 193.

 

Since your reading the first time seems about right, I'd suspect the 2nd reading.

 

Probably a smaller point, I usually fire 20 rounds over the chrono to get an average -

a higher sample size might help a little. 

 

But, as Sarge mentioned, something else

interfered (sunlight, the way you set up the chrono, the distance fired (muzzle

blast on the screens), etc etc.

 

Where in Canada are you?   I used to live in Toronto, Cornwall, Saskatoon

and Edmonton, over the years.

Yes, I also agree with Sarge as that was what I was expecting. I believe the contributing factor to the ridiculous velocities is that I had the ammo in a clear plastic bag and left it out in the hot sun for two hours before I chronoed the ammo. I didn't think it would have made a difference. I live in Saskatoon, and we are experiencing a heat wave at this time. Yesterday was the coolest day this week, so I will try this again, but keep my ammo protected from the sun as this week the temp will be about 4-6C hotter (93-97F),  and I will see what the velocities will be. If the velocities are the same, I guess I will have my chrono checked, and if they are 3-4 PF higher (as would be expected) then I know NEVER to leave the ammo sitting in the hot sun again :).

Edited July 13, 2017 by abb1

[Vmax606]

Put 10 rounds in plastic bag keep them in an iced cooler, 10 in cardboard box, 10 in a can in front of the car heater vent for 5 minutes. Test them at the same time and find out for yourself, instead of asking for other's opinions.

 

[ChuckS]

15 hours ago, abb1 said:

Okay, this kind of blew me away today.  I have always loaded 9mm major using 6.9 gr of WAC using a 124 FMJ at 1.15". I tested my rounds using a Caldwell G2 Chrono lasMarch indoors at 19C (66F) and a 10 group string averaged 1377 fps or a PF of 170. Today I had my ammo sitting in the sun (just where it was put), and it was 30C outside in the sun (87F). I decided to  chrono my ammo again (using the same chrono) for an upcoming match and an average of 10 rds chronoed at 1557 average or 193 PF. Can the temperature make the ammo go almost 180 FPS faster??? There were no real signs of pressure. Has anyone else noticed that big of a velocity change shooting in hot temperatures? This does not seem right......

33 PF above minor should do . I use more or less the same 9 major load and have not seen anything like this in the deserts of CA, AZ and UT. I think the first place I would look (assuming all ammo was from the same lot) is for instrumentation error. Really fast velocities could be a result of the chrono picking up some thing other than the bullet (gas, etc), weird lighting conditions, or a bad chrono. Try another instrument, stand back, watch the lighting. My results line up with your indoor example. Fastest I have seen is ~1420.

 

Later,

Chuck

Saskatoon? Say hi to Peter F from Chuck!

 

[Shmella]

3 hours ago, Vmax606 said:

Put 10 rounds in plastic bag keep them in an iced cooler, 10 in cardboard box, 10 in a can in front of the car heater vent for 5 minutes. Test them at the same time and find out for yourself, instead of asking for other's opinions.

 

You might as well just delete your account here then and call it a day.

[GrumpyOne]

4 hours ago, Vmax606 said:

Put 10 rounds in plastic bag keep them in an iced cooler, 10 in cardboard box, 10 in a can in front of the car heater vent for 5 minutes. Test them at the same time and find out for yourself, instead of asking for other's opinions.

 

Attitude
Please be polite. Or if not polite, at least respectful.
No bickering. Regardless of the subject matter.
Antagonistic, offensive, or quarrelsome tones are not acceptable.
No trolling. No alternate accounts.

 

The purpose of this forum is to share information. 

[Hi-Power Jack]

5 hours ago, Vmax606 said:

  Test them at the same time and find out, instead of asking for other's opinions.

 

 

I'm interested in the answer to this question - would be nice if someone answered

it instead of me having to run a complex test (ice box, and running my car heater

for 10 minutes)?

[Steve RA]

Put some in your cooler and the others out in the sun, that will give you the answer.

[Vmax606]

Did not mean to offend anyone. What I suggested is for him to find out FOR SURE OF WHAT HAPPENED, instead of having other people GUESSING what happened .

[Sarge]

1 hour ago, Vmax606 said:

Did not mean to offend anyone. What I suggested is for him to find out FOR SURE OF WHAT HAPPENED, instead of having other people GUESSING what happened .

But, that's what we do. This forum prides itself on being helpful. You didn't really offend anyone and what you said would have been laughed off if we were all sitting around drinking a beer. But when we type stuff it's easy to get misread. 

[AWLAZS]

Was your ammo all loaded at the same time? I have had the powder measure adjust its self when I was not looking and mess my chrono results up. 

 

Heat or cold can influence PF. I stopped using Ramshot Silhouette because of the change in velocity when the temperature was super hot. In Vt 60 degrees it was 175 and at nationals were it was 100 degrees 165.  I would heat my rounds up on the truck motor prior to testing them on the chrono so I knew I would make PF in Vegas.

 

 

 

[NickAument]

Shot the limited nationals in Reno in 92 or 93 was using Win231 for my 45 loads. I was from Cali at the time and before leaving temp was 70 degrees my PF was 185, well 2 days later in Reno about 35 degrees,  same load chrono's at 163PF!!

AWLAZS at a major match your loads will be pulled from you and kept by the RO's until it's your time to chrono, they won't let you heat them or do anything with them including

"rolling them in your hands to warm them up", ask me how I know!!

 

[Alan550]

3 hours ago, NickAument said:

Shot the limited nationals in Reno in 92 or 93 was using Win231 for my 45 loads. I was from Cali at the time and before leaving temp was 70 degrees my PF was 185, well 2 days later in Reno about 35 degrees,  same load chrono's at 163PF!!

AWLAZS at a major match your loads will be pulled from you and kept by the RO's until it's your time to chrono, they won't let you heat them or do anything with them including

"rolling them in your hands to warm them up", ask me how I know!!

 

But it matters what the RO's do with it in the meantime!  I run WST for Bianchi loads that are Minor for sure, but when the ammo got put in clear plastic bags in the sun for 2-3 hours, I got called to the chrono every time so they could fire from my gun.  It wouldn't make 120 PF in their 5" 38 Super and my ammo was 9X23 from a 6" barrel.  Even then, the "greenhoused" ammo was much slower than if it hadn't been in the sun.  (WST is inversely sensitive, hot temps slow it down.)

 

Alan~^~

Edited July 16, 2017 by Alan550
clarification

[R1_Demon]

I know this has been buried for a while, but I'm wondering if the OP ever figured out what the deal was?

 

I know a lot of people do talk about shooting their ammo on cold days and hot days and how the PF and FPS varies slightly.  However, I honestly believe that leaving the said ammo sitting out in the direct sun in a sealed bag could have caused this type of situation.  Especially if it was a clear, sealed bag where the sunlight just beat down on it for a good 2-3 hours before shooting it.  It's one thing to just take ammo out of a covered range bag and shoot it in hotter/colder temps than we loaded it or tested it in, but to have it actually just sit for hours in a sealed bag in hotter/colder temps before actually shooting it has to cause an affect with almost any powder to a certain degree.

 

I'd be surprised if it didn't cause this type of effect on his ammo.  I would actually agree with trying out the same ammo (if you had any left over) after it had time to cool back down to regular room temps (if this heated exchange did not cause a permanent effect to the ammo) and/or cool it down in a cooler, as someone did mention, and then try those rounds and see how they measure on the chrono afterwards.

 

So, I'm curious about this actually.  This would be a good test of this exact ammo again.  Take one batch and leave it sealed in the hot sun again, just as the same before, but another batch (made the same day, same press, same everything) that was in more controlled conditions (in a range bag in the car where sunlight wasn't a factor) and then take them both out and shot a string of each, one after another, and then saw if there were any differences regarding the "regular" range bag ammo and the "super heated" ammo in the sun.  I'll bet there is a big difference between the two just as the OP saw initially.

 

Then again, I might be wrong in all of this and it might not matter.  LOL!!! 

[MrPostman]

Last time I had a wild fluctuation like that the Chrono wasn't completely unfolded when I put it on the tripod. The 2 sensors were then a bit closer to each other than normal which added 100+ fps which I knew had to be wrong.

Sent from my SAMSUNG-SM-G935A using Tapatalk

[Hi-Power Jack]

1 hour ago, MrPostman said:

Last time I had a wild fluctuation like that the Chrono wasn't completely unfolded 

 

I've had that happen with my Chrony - if you open it incorrectly, the top part

sits on a little ledge and is not completely open - shortens the sensor distance, also.

 

Have to watch that, with the Chrony - don't know about other brands     

[jakfrost1]

Well I’ve had the completely opposite experience with my PF and heat...Chrono’d at 169+ home here in Canada in January, outdoors, -10c...got to the Florida Open in Frostproof Fla, +20c.  Chrono’d at 165.1...YIKES. The guy running the Chrono stage suggested, ( with some sarcasm), that I ‘might wanna check dem loads when I got home’...I stayed in Major, but by the skin of my teeth! 

 

My flying experience is that the opposite should be true, but can’t argue the facts. The only other explanation could be my Chrono is off I suppose. Anyway I’m loading to 170+ for the Nationals in August...8.4gr 3N38 125gr Zero HP, 1.1170 OAL, DVC 9 Major. 

 

Jim

[IDescribe]

I do NOT shoot 9mm major.  But as a generally safe practice, if I were going to try to repeat the process to figure out what happened, I'd be reluctant to heat up working 9mm major loads to see if I could duplicate the pressure.  Seems like asking for a problem.  I'd be inclined to download them, THEN conduct a test.  There's no reason to risk pushing them up that high with your normal loads, not really knowing what temp they were at when they reported such high velocities, and not knowing whether or not your attempt to heat the next test batch will end up even higher, and run the risk of a kaboom.

 

That said, producing a higher velocity with the same gun and the same bullet and the same charge weight means it was accomplished with higher average pressure, and more importantly higher peak pressure, and given the extra 180 feet/sec, MUCH higher peak pressure.  It's difficult for me to imagine with the pressures 9mm major typically run at that you would have driven those up to 1557 without serious signs of overpressure, so I would guess here that the chrono gave you a bad reading, for whatever reason.

 

OR... you could test loads from the same batch under normal conditions, and if they test as they should in normal conditions, just make sure you use them in normal conditions forevermore.   Be safe, sir.   
 

[bigedp51]

Below is a chart of rifle powders and to the right of the powder is the FPS change for each degree of temp change.

Pistol powders contain more nitroglycerin than the double base powders below and would be effected more by the temp change.

 

The military switched from RL15 a double base powder to IMR-4064 a single base powder for their long range sniper ammunition. This was due to the temp sensitivity of RL15 in Iraq and Afghanistan. The RL15 would change 1.52 fps for each degree of temp change and the IMR-4064 is only 0.45 fps change. It is the amount of nitroglycerin in the double base powders that effects its sensitivity to temperature. 

Edited July 7, 2018 by bigedp51

[IDescribe]

BigEd, where did that chart come from?  I would recommend no one pay attention to it.

Rather than lay out every possible pitfall of a chart like this (there's a boatload), I'm just going to say as a specific example:  It is absolutely preposterous to think that a load for .270 Winchester with 59gr of 4831 driving a 135gr bullet at 3,000 feet/sec will show a 0.36 feet/sec difference per degree Fahrenheit difference in temperature AND a load for .300 Weatherby Magnum with 75gr of 4831 driving a 200gr bullet 2,850 feet/sec will then magically show the same 0.36 feet/sec per degree Fahrenheit temp difference.  There is NO WAY that is going to happen.

A chart like that is useless with the same powder in the same caliber but different bullet weights, much less the same powder across different calibers, MUCH MUCH less from one powder to the next, and MUCH MUCH MUCH less from one powder to the next in different calibers at different starting temperatures in different rifles at different elevations with different primers under different phases of the moon.  This looks like something someone threw together with their own loads.   And we don't even know what loads were used.

Another clear example of the weakness of this chart:  H4831SC has a difference of .08 feet/sec per degree F?  Really?  So a hair more than 1 foot/sec per 12 degrees Fahrenheit?  Think about that.  How was that measured?  I'm pretty sure if you made a 40 round batch of 30-06 with 4831SC, cut it in half and chronoed the two 20-round batches of the SAME load that you'd get more than 1 foot/sec difference at the same temperature, so I'm wondering how someone measured that you get 1 foot/sec difference per 12 degrees F difference in temperature.  That's a fraction of the standard deviation for a single batch.  There's no way that was accurately measured.  There's no way to measure that at a resolution where something as precise as 0.08 feet/sec per degree F means anything.  

And now that I think about it, H4831SC and H4831 are the same chemical composition, so if temperature sensitivity were based on nitro content alone, AND this chart were meaningful, 4831SC and 4831 would have the same velocity diff per degree F diff instead of 4831 being almost 5 times higher than 4831SC.

Basically, BigEd, there's just no way for a chart like this to mean anything.