FPS velocity change per degree on various powders

[DIBBS]

There was a post on the Hide when it was on Scout.com regarding change in velocity per degree temperature change.

www.scout.com/military/snipers-hide/forums/5514-bolt-action-rifles/13858015-temp-sensitivity-data-for-most-common-powders-fps-deg?s

I found this mentioned on Accurate Shooter.com

I tried the link and couldn't get it to work. Is anyone aware of an inclusive chart, similar to the powder burn rate charts that are available, that shows the approximate change in velocity due to a degree in temperature for specific powders.. Since I do use some powders that are temperature sensitive, and shoot from 0-75 degrees, it would help me in deciding which old stock to use where.

This was some of the info that was posted in 2015. Do your results mimic this?
Also one poster stated
The rule of thumb I use is:
0.5 fps/degree F for single based powders (like Hodgdons extreme and most stick powders).
1.5 fps/degree F for double based powders (like MAGPRO and most ball powders).


I have several of the powders on the bottom of the chart that I haven't used in quite a while.... but I should use up the odds and ends... at some point.

Reposted in order of smallest to largest variance.

Varget .19 fps per *
H1000 .21 fps per *
H4895 .23 fps per *
H4350 .29 fps per *
H4831 .36 fps per *
Benchmark .44 fps per *
AA4350 .47 fps per *
Retumbo .49 fps per *
Imr4064 .53 fps per *
Imr8208xbr .59 fps per *
Imr4350 .64 fps per *
RL10x .71 fps per*
Imr3031 .73 fps per *
Alliant AR comp .77 fps per *
Hybrid 100v .78 fps per *
Ramshot Hunter .86 fps per *
Imr4895 .87 fps per *
Ramshot Magnum .87 fps per *
Alliant Varmint pro .89 fps per *
Ramshot Tac .91 fps per *
AA2520 .98 fps per *
Ramshot Biggame .98 fps per *
PP2000MR .99 fps per *
Magpro 1.01 fps per *
VV N150 1.08 fps per *
AA4064 1.11 fps per *
Imr4227 1.17fps per *
Imr4831 1.19 fps per *
HS-6 1.21fps per *
H110/W296 1.24 fps per *
VV N160 1.24 fps per *
Lil' Gun 1.31 fps per *
W748 1.32 fps per *
Imr4320 1.32 fps per *
Imr7828 1.36 fps per *
H414/W760 1.42 fps per *
RL17 1.42 fps per *
H380 1.44 fps per *
RL15 1.52 fps per * from 50* and up
RL25 1.59 fps per *
RL19 1.61 fps per *
H50bmg 1.64 fps per *
US869 1.68 fps per *
RL22 1.71 fps per *

Are the numbers above for these powders similar to the results you have experienced?

 

[acourvil]

No other info, but I think this might be the chart you are referring to. But the numbers do not all match your list.

 

[Jefe's Dope]

When taking speeds at my last CF match it was 12*. My average speed using 4350 was 2925. When zeroing my new ZCO this last weekend, my average FPS was 2929 at 71* indoors. That closely mimics what you posted above. DA will effect speed more so than temps.

 

[Ledzep]

Burn rate characteristics are unfortunately not very straight forward. The burn rate and temperature sensitivity can both change in the same cartridge with different bullet weights, or even bullets of the same/similar weight and different engraving forces. It will also change even more goin cartridge to cartridge.

Temperature sensitivity factors that other people find in their guns/loads can be a sorta decent guess, but it's usually best to test it yourself if you want the most accurate corrections.

For example, I've seen Varget anywhere from 0.15 to 0.37.

 

[918v]

Temperature sensitivity is cartridge dependent.

 

[MarkyMark007]

There was a post on the Hide when it was on Scout.com regarding change in velocity per degree temperature change.

www.scout.com/military/snipers-hide/forums/5514-bolt-action-rifles/13858015-temp-sensitivity-data-for-most-common-powders-fps-deg?s

I found this mentioned on Accurate Shooter.com

I tried the link and couldn't get it to work. Is anyone aware of an inclusive chart, similar to the powder burn rate charts that are available, that shows the approximate change in velocity due to a degree in temperature for specific powders.. Since I do use some powders that are temperature sensitive, and shoot from 0-75 degrees, it would help me in deciding which old stock to use where.

This was some of the info that was posted in 2015. Do your results mimic this?
Also one poster stated
The rule of thumb I use is:
0.5 fps/degree F for single based powders (like Hodgdons extreme and most stick powders).
1.5 fps/degree F for double based powders (like MAGPRO and most ball powders).


I have several of the powders on the bottom of the chart that I haven't used in quite a while.... but I should use up the odds and ends... at some point.

Reposted in order of smallest to largest variance.

Varget .19 fps per *
H1000 .21 fps per *
H4895 .23 fps per *
H4350 .29 fps per *
H4831 .36 fps per *
Benchmark .44 fps per *
AA4350 .47 fps per *
Retumbo .49 fps per *
Imr4064 .53 fps per *
Imr8208xbr .59 fps per *
Imr4350 .64 fps per *
RL10x .71 fps per*
Imr3031 .73 fps per *
Alliant AR comp .77 fps per *
Hybrid 100v .78 fps per *
Ramshot Hunter .86 fps per *
Imr4895 .87 fps per *
Ramshot Magnum .87 fps per *
Alliant Varmint pro .89 fps per *
Ramshot Tac .91 fps per *
AA2520 .98 fps per *
Ramshot Biggame .98 fps per *
PP2000MR .99 fps per *
Magpro 1.01 fps per *
VV N150 1.08 fps per *
AA4064 1.11 fps per *
Imr4227 1.17fps per *
Imr4831 1.19 fps per *
HS-6 1.21fps per *
H110/W296 1.24 fps per *
VV N160 1.24 fps per *
Lil' Gun 1.31 fps per *
W748 1.32 fps per *
Imr4320 1.32 fps per *
Imr7828 1.36 fps per *
H414/W760 1.42 fps per *
RL17 1.42 fps per *
H380 1.44 fps per *
RL15 1.52 fps per * from 50* and up
RL25 1.59 fps per *
RL19 1.61 fps per *
H50bmg 1.64 fps per *
US869 1.68 fps per *
RL22 1.71 fps per *

Are the numbers above for these powders similar to the results you have experienced?

this is total bullshit. like they said, it is cartridge dependent. and temperature dependent !

just select powders in 2 or 3 different categories like 'very temperature dependent', (middle) and small.

not some marketing numbers, which are lies.

the most stupid thing is that testin for freezing temperatures are done in summer. rifle-barrel needs to be cold/hot also!

 

[Mike Casselton]

I can see you have a lot of experience with actual pressure and velocity testing.

 

[918v]

the most stupid thing is that testin for freezing temperatures are done in summer. rifle-barrel needs to be cold/hot also!

There was an article online several years ago where they tested cold ammo during the summer in ambient temperatures through warm barrels and frozen barrels and there was no difference as long as they didn’t allow the ammo to cook in the chamber.

 

[EMorr]

I have often wondered about temp variability and testing it but the hiccup I see is not the ambient temp effecting the pressure but the temp change from the heat sinc effect from the cartridge sitting in a hot chamber. I mean if you chamber is around 200 to 300-ish degrees Fahrenheit (wild guess, obviously depends on rate of fire) and the round spends 5 seconds in the chamber versus 15 seconds in the chamber before being fired how much does that raise the temp of the powder and effect pressure and velocity?

 

[918v]

There is a guy named Denton Bramwell who tested this. Google him.

 

[Ledzep]

I have often wondered about temp variability and testing it but the hiccup I see is not the ambient temp effecting the pressure but the temp change from the heat sinc effect from the cartridge sitting in a hot chamber. I mean if you chamber is around 200 to 300-ish degrees Fahrenheit (wild guess, obviously depends on rate of fire) and the round spends 5 seconds in the chamber versus 15 seconds in the chamber before being fired how much does that raise the temp of the powder and effect pressure and velocity?

If your chamber is that hot you've got bigger problems than velocity creep.

In the real world, chamber temp is probably 75-100 F. Heat transfer from homogeneous 32 degree ammo is going to have to soak through the brass and start affecting the air/powder(mostly wood pulp) temp. 10 seconds isn't going to make a meaningful difference.

 

[MarkyMark007]

There is a guy named Denton Bramwell who tested this. Google him.

he is wrong about many things.

https://www.shootingsoftware.com/loadens.htm Bryan Litz show that this is not true.

https://www.shootingsoftware.com/ftp/Pressure Factors.pdf Denton wrote: Both barrel temperature and powder temperature are important variables

his testings and findings are very amateur.

so what is your point?

 

[918v]

he is wrong about many things.

https://www.shootingsoftware.com/loadens.htm Bryan Litz show that this is not true.

https://www.shootingsoftware.com/ftp/Pressure Factors.pdf Denton wrote: Both barrel temperature and powder temperature are important variables

his testings and findings are very amateur.

so what is your point?

That powder temperature affects velocity. Do you have a link to a more professional test?

 

[MarkyMark007]

for testing at real outside temperatures, no. just here and there some notes from other users.

but for some powders and cartridges I saw this page: https://www.wlcastleman.com/equip/shoot/t223/index.htm

 

[MarkyMark007]

Precision Rifle Powder and Bullet Studies

New vs Old Vihtavuori N140

Methods

 

[918v]

Have you ever tested this for yourself?

 

[Gil P.]

The results from other reloaders regarding temperature sensitivity has never matched my experiments. H4350 was gaining about 1 fps/degree in my rifle, while in another rifle I saw very little change in velocity from reloder 15 shooting at 70 degrees, and then went and shot at match in a different state at 20 degrees. Only change in my data was due to environment, I left the velocity numbers the same.

 

[MarkyMark007]

Have you ever tested this for yourself?

Every time for last 5 years I record velocity and temperature when I go to the range. But I often change something, so the exact data I don't have, but I have a lot of approximative data. But in my rifles I don't have large velocity swings between summer and winter. And in winter, I dont shoot a lot. So...

Mybe I will post some data, if I think they are relevant and usefull.

 

[Near miss]

I asked VV for temperature data and they refused to give me anything. The guy said they have tested it to be way too specific to be passed on as "data".

It indeed changes with bullet and cartridge and other variables. Along with the curve not being always even linear.

I do hope and asked they would collect the info and publish it, so someone could use it as a baseline for their own work but they might want to keep it to themselves.

I usually calc around 0.5ms / C when I want to prepare for longer distance without knowing the MV for that temperature yet. Gets me closer than just going totally wrong MV. I just true it to the correct value according to drop.


Thought experiment (usually worth skipping):
Because the material/chemical energy is set, you have energy leaving from the case by minimum the amount of heat the powder can withold, which may or may not linearly correlate with how the powder actually behaves ie. the final energy output.

Let's assume a typical 223 77gr load:
Energy required to heat 23.15gr of powder from 0C/32F to 20C/68F: NA - requires guessing.
Water: 126J (just for comparison)
Wood: 53J
So around 50J is at least taken from the system.
5g/77gr leaving the muzzle at 860ms=1845J
5g/77gr leaving the muzzle at 849ms=1798J
So roughly 10ms/33fps is bound to be lost with that energy the powder lost when it freezed.

This gives a powder sensitivity factor of 1%.
While it usually (I actually do not know) hovers around 0.8% to 2.4%, it seems that the bulk of energy dissipation originates from mere powder heat energy being drawn out from the case itself.

Or I do not know, all of this could be total bullcrap if I failed some math along the way.

 

[Near miss]

I usually calc around 0.5ms / C when I want to prepare for longer distance without knowing the MV for that temperature yet. Gets me closer than just going totally wrong MV. I just true it to the correct value according to drop.

Lmao just realized my old standard of guessing MV aligns pretty much perfectly with the 1% sensitivity factor. 0.5ms/C = 10ms/20C

 

[MarkyMark007]

in 223 I have with Vihtavuori N550 powder maybe ~ 1m/s / 1°C; with N140 maybe half of that. With Reload Swiss RS60 maybe ~1,5m/s / 1°C...

but it's hard to see EXACT value, because like I said, I often change something (primer, OAL...) and barrel is in different condition after 500 shots from summer to winter.
It can be faster if it was new or it is not clean, it can be slower if the barrel is very clean...

 

[acourvil]

I do not have real data to support this, but anecdotally I think I have observed that with H4350 temperature differences have greater effect on max loads than on mild loads.

 

[BuildingConceptsllc]

I do not have real data to support this, but anecdotally I think I have observed that with H4350 temperature differences have greater effect on max loads than on mild loads.

Yeah, I would agree with that. I don't have the data either but temp difference does tend to effect the hotter loads more than the mild ones for sure. That may be just a function of being able to notice it more because it's hotter and closer to pressure, but it seems like it's a bigger jump per degree the hotter the load is

 

[OkieMike]

This is based on my own observations of my own loaded ammo. So the sample size is small and in no way authoritative.

Most of the powders I've loaded with have been relatively stable across a decently large temperature spread.

I had a stiff load of H1000 that worked well... Until I shot it on a hot day (~95°F) and had some sticky bolt lift.

Other temp sensitive powders have done well for me... I wouldn't see much of a velocity change at all until ambient temps dropped to around 40° F. Then velocities dropped like a rock.

I guess I could go back, compile all the data and make myself a chart. But that's a lot of work that I just don't feel like dealing with.

Just my own experience.

Mike

 

[Mike Casselton]

Does anyone that's currently in Montana or somewhere that's experiencing severe cold temps want to test this?

5 rounds at 75°+ from your shirt pocket.
Follow that up with 5 rounds that have spent at least two hours in their freezing assed cold and immediately fired. 6 hours would be better. Fill a 5 round mag, toss it into a ziplock and leave it outside for the required test.

That should give a bit of data to discuss.