Effects of Cold on Muzzle Velocity

Boomer

Boomer

CGN Ultra frequent flyer
Uber Super GunNutz
Rating - 100%
21   0   0
Location
Somewhere on the Hudson Bay Coast
Since I began working on the load development for the .375 Ruger earlier this year, I have wondered just how much effect the cold has on our loads. The weather this morning was nearly perfect for a test; sunny, -32 and a light wind held the windchill to only -45 which would have no effect on the test, but would make it much more pleasant than -50. I tried to get a good coverage of high and low velocity loads from both large and small capacity cases, but I'm afraid I don't have any large capacity small bores. The warm weather velocities listed were from the same loads in the same guns in temperatures between 10 and 20 degrees C.

Remington M-7, .243 Winchester, 22" 1:10 Lilja:

55 gr Nosler Ballistic Tip - 45.0 grs of Varget - Remington 91/2M Primer, Winchester brass
Warm - 3984 fps
Cold - 3835 fps
loss - 149 fps

Brno 602, .375 Ultra, 20" 1:12 Smith:

380 gr Rhino - 84.0 grs H-4350 - Remington 91/2M Primer, Remington Brass
Warm - 2317 fps
Cold - 2263 fps
Loss - 54 fps

300 gr TSX - 90.0 grs H-4350 - Remington 91/2M Primer, Remington Brass
Warm - 2603 fps
Cold - 2585 fps
Loss - 18 fps

Small Game Load
270 gr Hornady - 18.0 grs Unique Remington 91/2M Primer, Remington Brass
Warm - 1260 fps
Cold - 1072 fps
Loss - 188 fps

Mossberg 590, 12 gauge, 20" factory barrel:

3" 600 gr Brenneke factory load
Warm - 1335 fps
Cold - 1130 fps
Loss - 205 fps

Ruger Redhawk, 4" factory barrel, .44 Magnum:

325 gr WFN hard cast, 20.0 grs H-110, Federal LP Magnum Primer, Winchester Brass
Warm - 1190 fps
Cold - 1094 fps
Loss - 96 fps

S&W M-27, 6" factory barrel, .357 Magnum
195 gr hard cast SWC, 13.0 grs H-110, Federal SP Magnum Primer, Winchester Brass
Warm - 1120 fps
Cold - 1061 fps
Loss - 59 fps

Suffice to say that temperature can have a profound effect on velocity. I find it curious that there was so little difference in the 300 gr TSX velocity between cold and warm temperatures. Can any conclusions be drawn? Probably not, but if you sight in your rifle in the summer, it is prudent to resight it for a winter hunt. The effect of a lower muzzle velocity combined with denser air could really shake your confidence in your flat shooting rifle.
 
That's some great info. Always better to have real world numbers instead of the assumptions that are sometimes made from behind the keyboard. Great work Boomer, good to see that you keep good notes......
 
Hi,

Just wondered as you have such good data anyhow: Was there any trend in the consistency of the velocities across temperatures?

RG

<><
 
Interesting. I'e shot in the cold, but never chronographed the loads.
Ever chronographed .22rf in the cold? It seems to be very reduced in velocity, and there seems to be a lot of unburned powder and heavy fouling.
 
Years ago, when our northern people were known as Eskimos, they had the cold weather bit figured out.
A well known American gun writer of the day went up north with his new 222 Remington, to shoot seals with the Eskimos. A seal had his head above the ice at 200 yards when the shooter rested his rifle for a perfect shot. The Eskimo said, "Better aim a little high." The shooter thought to himself, no way, he was sighted in for dead on at 200 yards. He squeezed off a shot and hit the ice under the seal's head. The Eskimo just looked at him and said, "the rifle shoots a little lower in cold weather!" And this was a gun writer in a US magazine.
 
Ruffed Grouse said:
Hi,

Just wondered as you have such good data anyhow: Was there any trend in the consistency of the velocities across temperatures?

RG

<><
Click to expand...

That is something I considered including in the first post, but because I have such a small sample of cold weather velocities, I can't be sure if the extreme spreads I observed today were the result of temperature alone, or if other factors were at work. With such a small sample, a case could easily be out of spec, and if I was going to be precise, I would select cases by weight rather than just shooting ammo as it came from my ammo box. I'm not a ballistician, so I have the freedom to conduct a test on the spur of the moment without concerning myself with what some might consider important considerations.

My .375 seems to produce pretty consistent warm temperature velocities, yet the extreme spread this morning was almost double of anything I have previously recorded with 300 gr TSX's. The Brenneke slugs previously had an extreme spread of 14 fps in warm weather, and admittedly I have only ever shot a small number across a chronograph , but today the extreme spread was 154 fps. The small game loads in the .375 had an extreme spread this morning of 61 fps, compared to 44 fps in the summer. The extreme spread for the .243 load was 88 fps this morning, and 24 fps in the summer. As you can see, it would be incorrect to make assumptions based on extreme spread from such a small sample, and without making an effort to control variables such as case capacity or the number of times a case had been fired. Even so, the velocity dropped significantly in most of the examples and that was the purpose of the test, to see how ammunition I might use in the field in cold weather compared to similar ammo I had measured in the summer.

I suppose I could load up some match bullets in weighed Lapua cases and run the test again with my .308 target rifle, but my curiosity has limits. Based on my observations today I would be tempted to say that the cold has a detrimental effect on extreme velocity spread, but this test doesn't confirm it.
 
tiriaq said:
Interesting. I'e shot in the cold, but never chronographed the loads.
Ever chronographed .22rf in the cold? It seems to be very reduced in velocity, and there seems to be a lot of unburned powder and heavy fouling.
Click to expand...

I don't shoot rimfire very much, but a pal of mine who has some very accurate rimfire rifles notes a significant loss of accuracy in the cold, as well as the fouling you refer to. I think part of the problem is the bullet lube which hardens in the cold, and the fact that the velocity might be lower and the air denser results in the bullet becoming sub sonic at closer range, but this is pure conjecture.
 
H4831 said:
Years ago, when our northern people were known as Eskimos, they had the cold weather bit figured out.
A well known American gun writer of the day went up north with his new 222 Remington, to shoot seals with the Eskimos. A seal had his head above the ice at 200 yards when the shooter rested his rifle for a perfect shot. The Eskimo said, "Better aim a little high." The shooter thought to himself, no way, he was sighted in for dead on at 200 yards. He squeezed off a shot and hit the ice under the seal's head. The Eskimo just looked at him and said, "the rifle shoots a little lower in cold weather!" And this was a gun writer in a US magazine.
Click to expand...


I have to re sight my rifles for cold weather then again in the spring when it warms up - at least those rifles I use in the cold. The trouble with some experts isn't their knowledge or lack of knowledge, but that they sometimes won't give other folks credit for knowing something. Good info as always.
 
Boomer,

Thanks for the data. Small samples aside it's interesting that it seems there might be a bigger spread. Of course it will take larger sample sizes to properly characterize the variance than to characterize the mean, but thanks nonetheless for the interesting results. Limited data are better than speculation!

RG

<><
 
Gatehouse said:
Was the H-4350 form the newer "Extreme" line?:)
Click to expand...

Yes, both the Varget and the H-4350 was purchased at the same time and both are "Extreme" powders. The H-110 was also purchased at this time, but it is not an "Extreme" powder.

I'm not surprised that the temperature effected the H-4350. The powder company's concern was for shooters who get themselves in trouble with excessive pressure in areas of the world that experience high temperatures. It shouldn't be a surprise to find that powder that is designed to produce a certain pressure parameter at high temperature would show a drop in pressure at low temperature. It is unfortunate that Hodgdon's advertised the powders as temperature stable rather than high temperature stable, but they are in the business of selling a product.

I did shoot some 30 year old IMR 4831 that I did not include in the original post because the velocity was so low. The load was 100 grs behind a 270 gr Hornady which averaged 2496 fps with a 270 gr Hornady. That same load with new H-4831 produced 2813 fps in warm weather.

Now and then we get questions concerning the use of old powder and many of us reply that it isn't a problem provided the product was properly stored throughout it's life. Again this was a small sample, but based on what I saw today, I am inclined to think that over long term storage powder looses energy, and if combined with low temperatures that loss of energy becomes more significant.

I also know from my blasting work that explosives have a specific shelf life, in fact commercial explosives are only guaranteed for1 year from the date of manufacture, and many explosive products have a specified temperature range. I discovered the hard way that when you exceed either the age or temperature range, some products loose a great deal of energy or simply don't work at all. That is something to keep in mind with propellants as well.
 
I discovered the hard way that when you exceed either the age or temperature range, some products loose a great deal of energy or simply don't work at all
Click to expand...
and some with NG get that nasty crystalline layer on the outside of their casing and work real well :)

I wonder if we know what happens with some (or any) primers when they get real cold...could they also contribute (or rather reduce) the brisance.
 
Some of us have shot wax or rubber bullets in our handguns using the primer as the propelling charge. I suppose you could measure the velocity of a wax bullet propelled by a primer at various temperatures to determine what effect temperature has on the primer, although I doubt if wax would be the ideal projectile at -35.
 
I had some H-4350 and some IMR 4350 loaded in a 30-06 and put a few shells of each in the freezer and the some in my pocket. I cronyed them back to back and came to the conclusion that the H-4350 really does what it is supposed to in regards to temp sensitivity as compared to the IMR.
 
a possible answer

the .375 H&H is loaded to very low maximum pressure, around 42,000. This was deliberate, as it had to function at 10C in Britain and at 45C in Africa. The pressure rise with temperature was known in 19Century.
This also means that a small percent pressure change per degree of temp in a cartridge loaded to 42,000 is necessarily smaller than the same percent pressure change in a cartridge loaded to 60,000.
or so it seems to me.
 
Interesting results, Boomer. Thanks for posting. I'm assuming that you let the cartridges acclimatize to the ambient temperature at the time of the test and they weren't fresh out of the house,vehicle or your pocket?
 
Ruger No.1 said:
Interesting results, Boomer. Thanks for posting. I'm assuming that you let the cartridges acclimatize to the ambient temperature at the time of the test and they weren't fresh out of the house,vehicle or your pocket?
Click to expand...

The ammo was in the box of my pick-up an hour before I left home. The air temperature was -32 as was the temperature of all the ammo and the guns. What little heat was present from the sun would of been more than made up for by the wind.
 
You must log in or register to reply here.
Back
Top Bottom