Cold temp affecting terminal performance of plastic tipped bullets

[Ruger1Melch45]

Is atmospheric drag really enough to melt lead? If this were so, all-lead bullets would melt before arrival on target. Plus, the ballistic coefficient would be unstable and continually degrade. Some might never even get there.

I maybe wrong, but my instincts tell me that even a bullet sent from a superheated chamber at +/- 1,900 mph through -20°F is still going to arrive pretty darn cold.

This may need a physics degree to solve, I don't know what the thermal coefficient of hardness is for lead. Does anyone have an ASTM manual?

I'd just solve it with a follow-up shot. It takes much less time than a Bachelor of Science.

You are so right. Whats next ? We need to worry about the outside temp when hunting because if it is too cold out that the bullet may not perform right because the animals skin temp will be colder thus making it harder and more rigid for a bullet to penetrate ? Heck....maybe I have been thinking wrong all along and will need to bring my 40mm with me just in case of cold weather so I get better penetration.

 

[bigngreen]

This is getting WAY over thought, we are talking about changing bullet performance by holding a round in your hand for a few minutes before shooting it, think about it!! The colder air is more dense and has more friction than a warm day so if it's the friction of the air changing the bullet by heat it should be more affected on the cold days than the warm right??

 

[Pdvdh]

Sneak in close and put the muzzle into the fur. Take the air temp and bullet flight out of the equation. No more worries...

 

[WalksLikeADeer]

Has anyone else ever experienced this? I'm talking -20 or below and the bullet mushrooms, but not to the degree when it's warmer out. I've noticed that the same bullets in similar distances kill a lot better when it's warmer, shedding some weight and dumping more energy into the animal. Just wondering if anyone else has experienced this or if I'm imagining it.

There are a lot of good points brought up to as why the bullets are less effective at extreme low temperatures and I would like to suggest that it is combination of all the factors.

Velocity is reduced by colder temperatures(even with extreme powders), the air is denser causing more drag, the animals cold skin may be more resistent, etc.

In addition, the bullet is starting out -20 degress and I would reason that it would take longer to heat up than say a bullet at 70 degrees, especially at the core, given the short duration of flight, thus making it less viscous at impact.

I would be interested in seeing ACTUAL velocity numbers(not just balistic therory) at say 200 yds between -20 and 50-70 degrees F.

 

[Pdvdh]

I would be interested in seeing ACTUAL velocity numbers (not just ballistic theory) at say 200 yds between -20 and 50-70 degrees F.

Ballistic theory is as accurate as any other method imaginable or available. The ballistics programs stopped being theory years ago.

 

[bigngreen]

There are a lot of good points brought up to as why the bullets are less effective at extreme low temperatures and I would like to suggest that it is combination of all the factors.

Velocity is reduced by colder temperatures(even with extreme powders), the air is denser causing more drag, the animals cold skin may be more resistent, etc.

In addition, the bullet is starting out -20 degress and I would reason that it would take longer to heat up than say a bullet at 70 degrees, especially at the core, given the short duration of flight, thus making it less viscous at impact.

I would be interested in seeing ACTUAL velocity numbers(not just balistic therory) at say 200 yds between -20 and 50-70 degrees F.

My 28 Nosler launching a 177 gr Hammer impacts at 200 yards at -20 at 2827.8 fps and at 70 degrees 2869.2 fps. A .199 second flight time by the way.

 

[Canhunter35]

Without a verifiable experiment, it's impossible to say one way or another. I've merely observed that plastic tipped bullets seem to expand more when it's warmer and was wondering if anyone else has noticed this, which seems only one person has.

I never said the bullets failed or anything, only worked differently. This isn't a boo hoo I made a poor shot why didn't my bullet magically kill whatever I was shooting thread.

Consistently while shooting coyotes in cold weather my 168 amaxs leave a smaller hole at any range than when it's warmer. For my preferences, I prefer the smaller hole. They are dead all the same and fur isnt damaged as much. With the same bullet I shot my whitetail this year at 327 plus yards while I set down my range finder and dialed while he was running away, the amax worked great. Entered in front of his flank and exited the opposite side of his neck...that bullet retained enough of its weight to punch through a whitetail while inflicting massive damage. If it had been -20 or -40, perhaps the bullet would've done the same, but with less damage on its way through...still a successful kill either way.

Logic tells me air temp shouldn't make a lick of difference on the bullets terminal performance, but I've observed that it seems to. I repeat seems to, it's not a verified experiment.

 

[WalksLikeADeer]

Ballistic theory is as accurate as any other method imaginable or available. The ballistics programs stopped being theory years ago.

I agree they are close, but another method that is imaginable and available is to verify trajectories in field conditions.

The reason I was saying actual velocities, is to get real numbers from the OP's loads and conditions since we are discussing extreme low temperatures in particular. I was wondering if there may be other factors not accounted for in theory in extreme conditions that actually effect velocities such as the diameter of the bore at -20 degrees or other unaccounted for factors. Either way, it would either verify or bring about question to theory... which is a good thing.

Hornady argues that ballistic theory developed years ago is not as accurate it could be based on a bullets actual B.C. changing during flight and not fixed as used in most ballistic calculators, hence their development of the 4DOF calculator. Although the corrections are minor, they are measurable.

Regardless, I would not shoot at an Elk from 1000 yds based on theory without verifying trajectory in real life.

 

[Pdvdh]

Regardless, I would not shoot at an Elk from 1000 yds based on theory without verifying trajectory in real life.

Yes, but verifying POI at 1000yds from any rifle is more complex than comparing the change in velocity caused by different outdoor temperatures or atmospheric density. Nothing is simpler or more accurate for comparing differing downrange velocity than a properly fed ballistics program.

 

[knapper]

Has anyone else ever experienced this? I'm talking -20 or below and the bullet mushrooms, but not to the degree when it's warmer out. I've noticed that the same bullets in similar distances kill a lot better when it's warmer, shedding some weight and dumping more energy into the animal. Just wondering if anyone else has experienced this or if I'm imagining it.

Dear Sir; I think that your statement is base on faulty assumptions.. Let me explain my reasoning.. I do not have the expert equipment on had to prove my reasoning but let me try??I shoot two main rifles and the calibers are as follows.
1. a 300 Win Mag. 73 grains Alliant RL 22, 190 grain Hornady ELD X.. Gets me around 2900 FPS..
2. Also a 300 Win Mag, necked down to 7 MM, Again, Hornady 180 Grain bullet gets me around 3050 FPS, with 69 grains of H1000.. Both rifles use a 28 inch barrel..
When shooting a mile at a coyote, from a well concealed ,slightly higher prone position and the bullets are traveling at better than twice the speed of sound..When they get there, they are HOT and I don't care if the surrounding air is 30 Degrees below zero and that is why I use the bullets that have those protected tips.. When your bullet is going that fast and that far, the tip will melt and deform, affecting accuracy...

 

[Hand Skills]

This is getting WAY over thought, we are talking about changing bullet performance by holding a round in your hand for a few minutes before shooting it, think about it!! The colder air is more dense and has more friction than a warm day so if it's the friction of the air changing the bullet by heat it should be more affected on the cold days than the warm right??

Absolutely. The idea gas law gives us something like this;

Air is like 25% more dense on a cold day.

What's interesting is the speed of sound decreases with temperature. One might expect the speed of sound to increase with density. This is called acoustic impedance. I'm no rocket scientist, so while I can't comment on how this affects supersonic pressure envelopes, it's obvious to me that a bullet experiences greater resistance to inertia (and thus friction) during flight on a cold day, just type a cold temp into any balistics calculator. How much influence does the pressure wave around the bullet have on impact? How much bigger is that envelope of super compressed air? I know it's bigger, I can SEE it on colder days.

 

[Canhunter35]

Dear Sir; I think that your statement is base on faulty assumptions.. Let me explain my reasoning.. I do not have the expert equipment on had to prove my reasoning but let me try??I shoot two main rifles and the calibers are as follows.
1. a 300 Win Mag. 73 grains Alliant RL 22, 190 grain Hornady ELD X.. Gets me around 2900 FPS..
2. Also a 300 Win Mag, necked down to 7 MM, Again, Hornady 180 Grain bullet gets me around 3050 FPS, with 69 grains of H1000.. Both rifles use a 28 inch barrel..
When shooting a mile at a coyote, from a well concealed ,slightly higher prone position and the bullets are traveling at better than twice the speed of sound..When they get there, they are HOT and I don't care if the surrounding air is 30 Degrees below zero and that is why I use the bullets that have those protected tips.. When your bullet is going that fast and that far, the tip will melt and deform, affecting accuracy...

I agree...it makes no sense, but I'm wondering if anyone else has ever noticed this...

 

[Bigaldepr]

I would look to the propellant rather the hardness of the copper and lead. In general a chemical reaction speed doubles with each 10° C temperature increase and decreased accordingly. Some propellants are more temperature sensitive than others. See the following study:
http://precisionrifleblog.com/2016/06/19/powder-temp-stability-hodgdon-extreme-vs-imr-enduron/
Sorry I cannot use links yet so cut and paste.

 

[WalksLikeADeer]

My 28 Nosler launching a 177 gr Hammer impacts at 200 yards at -20 at 2827.8 fps and at 70 degrees 2869.2 fps. A .199 second flight time by the way.

bigngreen, Thanks for the input. That is interesting to know. Not a very significant difference in velocity for such a large tempurature swing. Glad to know someone has actually measured velocities at those tempurature ranges. I don't live in an area where I can shoot at -20 and dont think I want to either!