Powder temp and muzzle velocity

[Sherlock]

So, I’m out here in Colorado on my sons buck and bull hunt. Pretty cold morning the day before the hunt begins. Wondering about muzzle velocity at varying powder temps. Is there a way to find this data online? I’m using Nosler accubond 168gr for 7mm Rem Mag. Listed at 2880 fps for 59 deg, about what we zeroed at. Wondering what that would be at powder temp of say 10 degrees.

 

[roadrunner]

Same, the heat of combustion will be the same.

The POI downrange may change because of air density due to temp.

 

[willfrye027]

Hand loads or factory ammo?

A lot of the handloading powders will have a general fps/degree of temp correlation. But that will be in a specific cartridge over a specific temp range.

honestly I would not worry about it, I’ve made some long shots in temps that were 75 degrees colder than my home range and it was not an issue.

If using a historically temperature sensitive powder like RL25/26/17/19, ball powders, etc then maybe it would be interesting to check dope.

Best thing to do is shoot a couple rocks in the field at the longest range you would consider shooting an animal to see if your trajectory is affected.

 

[Ballistic]

Folks can say all they want about temp insensitive powders not changing with temps - and could be right.
What’s missing (and is a major part) is how do the rest of the components react to temp changes. The primer/brass/bullets/barrel also need to be considered.

Every gun will react differently. I have one rifle that speeds increase 30 fps when temps drop below 32. Another speeds drop 40 fps under 32. Another is hardly affected. And all 3 are using the hodgden extreme powder. Double based powders such as reloder powders have also shown spikes in speeds at low temps. Or is it the other components……
Leave your gun out in the cold temps and check its speed and zero. This will not work by taking your warm rifle out of your heated pickup and shooting it in the cold. Take good notes.

 

[Sherlock]

Hand loads or factory ammo?

A lot of the handloading powders will have a general fps/degree of temp correlation. But that will be in a specific cartridge over a specific temp range.

honestly I would not worry about it, I’ve made some long shots in temps that were 75 degrees colder than my home range and it was not an issue.

If using a historically temperature sensitive powder like RL25/26/17/19, ball powders, etc then maybe it would be interesting to check dope.

Best thing to do is shoot a couple rocks in the field at the longest range you would consider shooting an animal to see if your trajectory is affected.

Factory ammo

 

[Sherlock]

Thanks for the responses. Appreciate y’all’s help with me learning this stuff.

 

[Tristate]

I was watching some snipers talk one time about getting a fps boost while shooting in Iraq. They were letting ammo warm in the sun and claiming they were getting a little more performance. If I remember correctly they were shooting. 338 Lapua past 1 mile distances and getting pretty consistent kills.

Scientifically it didn't make a lot of sense to me but these guys were for real pros and I don't think they were full of it.

I consider it a lot like slope doping. Everyone likes to say it can be calculated but the real killers know you have to map it in practice first and write it down. Experience is what makes you lethal. Not so much theory and calculations.

 

[coloradoman]

I was watching some snipers talk one time about getting a fps boost while shooting in Iraq. They were letting ammo warm in the sun and claiming they were getting a little more performance. If I remember correctly they were shooting. 338 Lapua past 1 mile distances and getting pretty consistent kills.

Scientifically it didn't make a lot of sense to me but these guys were for real pros and I don't think they were full of it.

I consider it a lot like slope doping. Everyone likes to say it can be calculated but the real killers know you have to map it in practice first and write it down. Experience is what makes you lethal. Not so much theory and calculations.

If you’re shooting that far the curvature of the earth comes into play also.
Fact!-

 

[JPickett]

Different powders will definitely react to temperature. RL22 for example is a well known temp sensitive powder. Will it make a difference in the field? Probably nothing you would notice shooting at game from make shift backpack and the like rests. On a bench shooting at paper? That’s likely when you could see it

 

[gundog2]

I suspect that air temp would have more effect on the trajectory than it would on the initial muzzle velocity. You can check the effect of temperature on the trajectory of your bullet using some of the ballistic calculators available on the web.

 

[Chesterwyo]

If you’re shooting that far the curvature of the earth comes into play also.
Fact!-

Pretty bold of you to assume that the earth isn’t flat.

 

[Focoelkman]

I can’t answer your question , and it’s a valid one for sure. Probably lots of different perspectives and answers , but when ya get back post season, shoot, practice at the range when it’s cold so you know:

Wouldn’t recommend shooting at rocks when hunting?

Good luck and get after it!

 

[Utahlefty]

the biggest issue you're facing is that you don't know the powder profile that exists in the factory ammo you're using. there's no way to know without shooting at variable temps.

for handloaders there is a bit more data available.

TLDR: anticipate a 25-30 fps diff in colder temps compared to the data listed on the box, witch under 400 yards won't make an appreciable difference .

long answer:

powders can be very stable **for the cartridges they're developed for** (H4831 and .270 win for example) but not so much for alternate applications (H4831 in a .470 nitro for example)

using the former example, I've recorded less that 15 fps diff from 10* to 90*

using the latter example, I've recorded a 30 fps diff from 10 to 70* and a 60 fps diff between 70 and 110* (important in a double rifle that you need to make sure the barrels aren't crossing and necessitating three loads based on anticipated temps)

sum: outside an intended purpose you can't say whether an powder is temperature insensitive or not. you have to test it.

for factory ammo, you have to test it period.

that said, your unlikely to lose more than 30 fps except in extreme temp variations.

 

[roadrunner]

I used to think all the "stuff" made a difference abd mattered; specific powder measure, categorizing bullets by weight before loading, bullet seat depth based off the lands, etc.

For a standard hunting load, it doesn't matter for shots under 400 yds.

 

[Sherlock]

Appreciate all the feedback. My son managed to get his 1st his bull today. At 290 yards, we didn’t have to worry about the temperature effects.

 

[deadibob]

Temperature can make a big difference. Some powders are temp sensitive and others not as much. Hodgdon “extreme” powders are less affected than some others. There are some powders that change enough that a max load worked up in the winter at 30* can blow the gun up shooting the same load in summer at 100*

Always work up max data in warmer temps.

At the 50bmg world shoot in Raton every July 4th you will see the serious competitors all keep their ammo in a warmer. I saw one guy doing it the high tech way by letting his truck idle and keeping rounds inside his tail pipe.

 

[Ballistic]

Appreciate all the feedback. My son managed to get his 1st his bull today. At 290 yards, we didn’t have to worry about the temperature effects.
View attachment 125871

Good job and good shooting on his part. A majority of hunters can’t hit well at that distance.

 

[ElmerFudd]

Standard powders will change about 2 fps per degree F. Temperature insensitive powders change about 1 fps per degree F. You could record temperature and chronograph your loads on a hot summer day and cold winter morning to get as much variation as you can. Loads developed showing no high pressure signs in cold weather could produce excessive pressure on a hot day. Metal can be 30+ degrees above air temperature if out in the sun on a hot day. Keep that in mind.