Cold temp affecting terminal performance of plastic tipped bullets

[Pdvdh]

bigngreen didn't measure those velocities. He used ballistics program theory to provide that velocity data.

 

[WildRose]

The RPM's of the bullet makes a big difference on blowups and they blowup from the base.
Reading this article has made me wonder about bonded bullets with the heating in flight. Does this affect the bonding properties

If they get hot enough to melt the jacket and or lead the bonding agent won't matter anyhow.

 

[Mark Abrahamsen]

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

I've actually noticed this in nd when u will see a 6.5 eldx bullet expand perfect in the summer months when the air temp is 70 to 90 degrees but in winter in sub zero temp it's very common to get bullets that will act like a fmj enough so that one colder Hunting days I will limit My shooting range

 

[Mark Abrahamsen]

I've actually noticed this in nd when u will see a 6.5 eldx bullet expand perfect in the summer months when the air temp is 70 to 90 degrees but in winter in sub zero temp it's very common to get bullets that will act like a fmj enough so that one colder Hunting days I will limit My shooting range

For what it's worth I've allso tried shooting nosler acubond long range bullets it ballistic gel at 1400 fps 70 degree from 5 feet and had zero expansion with a 300 blackout then shot the same 210g bullet from a 308 at extended rang so the impact velocity was estimated to be at 1400 and had very good bullet expansion I always contributed it to the flight must have warmed the the bullet enouf to make it softer that it expanded or possibly different riffling made the jacket weeker both were on days close to 70 degree

 

[RockyMtnMT]

For what it's worth I've allso tried shooting nosler acubond long range bullets it ballistic gel at 1400 fps 70 degree from 5 feet and had zero expansion with a 300 blackout then shot the same 210g bullet from a 308 at extended rang so the impact velocity was estimated to be at 1400 and had very good bullet expansion I always contributed it to the flight must have warmed the the bullet enouf to make it softer that it expanded or possibly different riffling made the jacket weeker both were on days close to 70 degree

I would be interested to know the stability factor of each of your test bullets. In our bullet testing this has been a key to good terminal performance.

 

[Bigaldepr]

Absolutely. The idea gas law gives us something like this;View attachment 84537Air 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.

Just some basic physics: The speed of sound in a gas is dependent on temperature and the molecular weight of the gas. Since we only shoot here on earth the speed of sound is only dependent on temperature. It has to do with how fast the molecules are bouncing around hitting each other. From this a bullet with the same MV can be supersonic on a cold day and subsonic on a warm day at the same point down range. The viscosity of air varies directly with temperature so on a cold day there is actually less drag and the bullet remains supersonic further down range. Except that the density of air varies as the inverse temperature and directly with pressure so the shock wave off the tip of a supersonic bullet tends to slow it down faster with higher density. Conclusion: There is a complex set of factors that effect the trajectory of a bullet and the longer the shot the more complex it gets.

 

[Hand Skills]

...From this a bullet with the same MV can be supersonic on a cold day and subsonic on a warm day at the same point down range. The viscosity of air varies directly with temperature so on a cold day there is actually less drag and the bullet remains supersonic further down range. Except that the density of air varies as the inverse temperature and directly with pressure so the shock wave off the tip of a supersonic bullet tends to slow it down faster with higher density. Conclusion: There is a complex set of factors that effect the trajectory of a bullet and the longer the shot the more complex it gets.

Certainly agree with the conclusion!

I'm impressed that you equate supersonic drag to basic physics too.

If what you say is true;

...The viscosity of air varies directly with temperature so on a cold day there is actually less drag and the bullet remains supersonic further down range.

Why are my drops greater on cold days?


I think I understand where you're coming from on this, but I'd like to see an example. Physical and acoustic impedance are very different things. Maybe we're shooting dramatically different calibers, with a super high BC I could see it, but most of the subsonic terminal performance I've encountered is with a .22LR...

Here is a chart for anyone who wants to run the numbers for themselves;

 

[Mark Abrahamsen]

I would be interested to know the stability factor of each of your test bullets. In our bullet testing this has been a key to good terminal performance.

I don't remember the bullet lenth of the 210 acubond long range bullets but I will look it up when I get home the 300 blackout is 1 and 8 twist and the 308 win was a 1/10 twist

 

[shaughn]

If I remember right..velocity loss/gain is about 1.5 fps per 2 F, which isn't a lot..though it is a factor and when we get denser colder air infront of the bullet this will further slow the bullet on way to the target...

My thought on this would be that the bullet while traveling the same distance as under optimum conditions, is... due to velocity loss from temperature and denser air... acting just like it would if it had traveled farther...so if your bullet at 600 yards performs in X manner, but your cold weather shot doesn't...but instead looks similar to those bullets shot at a greater range during optimum conditions...then the denser air is slowing the bullet..and that is why the bullet performance is lacking....

 

[Mark Abrahamsen]

I would be interested to know the stability factor of each of your test bullets. In our bullet testing this has been a key to good terminal performance.[/QUO

If I remember right..velocity loss/gain is about 1.5 fps per 2 F, which isn't a lot..though it is a factor and when we get denser colder air infront of the bullet this will further slow the bullet on way to the target...

My thought on this would be that the bullet while traveling the same distance as under optimum conditions, is... due to velocity loss from temperature and denser air... acting just like it would if it had traveled farther...so if your bullet at 600 yards performs in X manner, but your cold weather shot doesn't...but instead looks similar to those bullets shot at a greater range during optimum conditions...then the denser air is slowing the bullet..and that is why the bullet performance is lacking....