Cold temp affecting terminal performance of plastic tipped bullets

[Canhunter35]

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.

 

[Capt RB]

Drag from the atmosphere is enough to melt an exposed lead point. Not to mention the preheating that was started when the trigger was tickled. The speed in which your load changed at that temp would be far more of a factor imho

 

[Howland]

Drag from the atmosphere is enough to melt an exposed lead point. Not to mention the preheating that was started when the trigger was tickled. The speed in which your load changed at that temp would be far more of a factor imho

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.

 

[Capt RB]

 

[Howland]

Wow! Thanks @Capt RB, that was an eye opener!

I'm not sure if that has any effect on the observation that @Canhunter35 made in the OP because in your response you mentioned lead, but I'm glad I saw that.

I picked up a new AR-10 and topped it with a rather expensive (to me if not other folks here) scope and 20 MOA mounts because I just joined a club that has 600 & 1,000 monthly matches. I had been planning on starting load development with the Nosler Ballistic Tip 180 gr. because it has decent BC and has performed well on game in my .30-06.

I do know I tried one projectile with a ceramic tip insert (if memory serves me right), although I bought it for the molybdenum coating. I got good groups but the Noslers were a little bit better so that's what I went with.

Hmmm.

That's the kind of learning that I came here for. Nice contribution to member knowledge. Thanks again.

 

[Hand Skills]

Interesting question. It sure would be a lot of fun to test. In engineering, metals can be evaluated for DBTT (ductile to brittle temperature transition). Metals with a BCC (body centered cube) exhibit dramatic DBTT graphs compared with metals of the FCC (face centered cube) crystal structure, which are relatively 'athermal'. Both lead and copper are of the latter family, so the expectation from an engineering POV, performance should not be greatly affected by temperature.



http://www.thefabricator.com/article/metalsmaterials/the-structure-of-metal

 

[WildRose]

Wow! Thanks @Capt RB, that was an eye opener!

I'm not sure if that has any effect on the observation that @Canhunter35 made in the OP because in your response you mentioned lead, but I'm glad I saw that.

I picked up a new AR-10 and topped it with a rather expensive (to me if not other folks here) scope and 20 MOA mounts because I just joined a club that has 600 & 1,000 monthly matches. I had been planning on starting load development with the Nosler Ballistic Tip 180 gr. because it has decent BC and has performed well on game in my .30-06.

I do know I tried one projectile with a ceramic tip insert (if memory serves me right), although I bought it for the molybdenum coating. I got good groups but the Noslers were a little bit better so that's what I went with.

Hmmm.

That's the kind of learning that I came here for. Nice contribution to member knowledge. Thanks again.

If you want to stick with lead core tipped bullets look at the Nosler Accubond LR and Hornady ELD-X and I suspect you'll be much happier with the results.

 

[Canhunter35]

If you want to stick with lead core tipped bullets look at the Nosler Accubond LR and Hornady ELD-X and I suspect you'll be much happier with the results.

Actually the eldx is one of the bullets Ive noticed do this along with vmaxs, amaxs, and nosler ballistic tips. There performance is fine when it really cold, but much more like a monolithic hunting bullet that expands and punches through. But if it's warm, they seem to 'detonate' and do a lot more damage.
Yeah, I was wondering about super heating of bullet as it's fired, but taking a frozen bullet, and its under heat for only moment, how much heat could it uptake? Then I was wondering what is the wind chill effect at Mach 2 and it's -20 is?

 

[bigngreen]

If you want to stick with lead core tipped bullets look at the Nosler Accubond LR and Hornady ELD-X and I suspect you'll be much happier with the results.

You didn't even read the thread did you, just assumed it was about a bullet you don't like so you recommend the very bullets the thread is about!!

 

[Hand Skills]

Actually the eldx is one of the bullets Ive noticed do this along with vmaxs, amaxs, and nosler ballistic tips. There performance is fine when it really cold, but much more like a monolithic hunting bullet that expands and punches through. But if it's warm, they seem to 'detonate' and do a lot more damage.
Yeah, I was wondering about super heating of bullet as it's fired, but taking a frozen bullet, and its under heat for only moment, how much heat could it uptake? Then I was wondering what is the wind chill effect at Mach 2 and it's -20 is?

Indeed, it would be interesting to create a thermal model. I don't doubt your results. Heating at the base due to combustion, heating of the bearing surface due to friction in the barrel, and ogive/tip heating in the atmosphere. As I stated earlier, copper and lead are classified as athermal, as far as their mechanical properties are concerned. They both have very different thermal properties though, when it comes to heat transfer. For example copper conducts heat at a rate of 10x that of lead. It also has twice the specific heat capacity of lead. Maybe the bonding between the two is affected somehow with a larger delta T?

Perhaps it's wise to consider animal physiology as a variable with temperature too.

 

[Hand Skills]

I don't recover many bullets myself, but here is a 170gr core-lok we recovered from my friend's first deer on Monday. Impact velocity was ~2000fps, temperature was around 0F.

 

[BallisticsGuy]

I'm just not seeing how a few 10's of degrees of air temperature is going to materially affect the mechanical properties of copper and lead under those conditions when it takes a few hundred degrees to have substantive effect in non-ballistic situations.

If this effect is something that really happens reliably then I think what we have here is new experimental territory crying out to be explored that might just illuminate something that should seem terribly obvious in hind-sight. Any new experiment physical sciences tends to end up with something unexpected climbing out of it so this is likely to be no different.

The amount of heat input into a bullet during its ride down the bore is substantial that heat doesn't just bleed off suddenly. They're still burnin' hot after leaving the muzzle whatever the air temperature is and a couple seconds (tops) of flight time is not a lot of time to bleed that heat off. I don't see how air temperature is going to be relevant or at least significant in any way. The bullet starts stupid hot and then is heated additionally from aerodynamic drag so the bullet is not experiencing the air as being cold (think SR-71 fuel tanks expanding and sealing up from Mach 3 temps). At best the bullet perhaps sees it as a little tiny bit less hot than it otherwise would. Then when the bullet actually strikes something it gets ridiculously hot (pound in a nail with a hammer and then touch the nail head to feel this effect) particularly when striking targets at speeds which cause expansion/deformation.

 

[Canhunter35]

It sounds ridiculous to me too, but I've been noticing a difference in bullet performance. The temperature seems to be the variable, but there's nothing saying that is the variable affecting. Just wondering if anyone else has noticed anything similar

 

[BallisticsGuy]

I don't want to say ridiculous but I might go so far as "dubious" or even "highly speculative".

So, you're shooting meat right? Then there's definitely one more large set of variables there. The consistency/tone of the meat and connective tissues (could be seasonally related), exact angle of projectile entry and what bones, tissues and organs were impacted not to mention the mental state of the critter (was it all tensed up & flooded with adrenaline) was it at top/middle/bottom of the natural breath cycle, etc... not to mention impact velocity which will be the major contributor to bullet deformation.

I'd really like to undertake or at least read a study exploring this. It's almost certain to have purely academic results but that's right in my wheelhouse. I love reading purely academic studies.