bullet temperatures

[DaveTooley]

I ran across this on a thumb drive and thought I'd put this out there.

 

[clowdis]

Interesting, it seems the temperature of the bullet in the groove marks exceeds the melting point of lead, although very briefly. Explains why, at the range in the pits, you only pick up a freshly fired bullet once!

 

[paperpuncher]

Interesting, it seems the temperature of the bullet in the groove marks exceeds the melting point of lead, although very briefly. Explains why, at the range in the pits, you only pick up a freshly fired bullet once!

Yep I did that at Perry the first time I was ever in the pits My digital thermometer can confirm that article

 

[DaveTooley]

It all makes sense. The highest pressure on the jacket is going to be on the lands. I had some problems with blowing up bullets. Getting the gray comet tail on a target at 10 yds. Then poof. I turned a piece of plywood at a 45 and started shooting through it. Finally got an imprint of a sideways bullet on a target behind the plywood. The lead appeared to be leaking at the junction of the ogive and body. Probably a fracture in the jacket from the pointing operation.

 

[STS]

This is a pretty good example of 'comet tails' on the target. A well worn first inch or so, that is somewhat larger that bullet diameter, will yield cracked jackets and molten lead leaking out as it passes through the target. My first .17 Mach IV started doing that at about 3600 rounds with about 1 in 10 bullets 'smoke trailing.' Then by 4000 rounds all bullets were doing it. I finished it off in a dog town at 4060 rounds and committed it to the trash can. When I took it off you could drop a bullet in the breech and it would stop about 2 inches past the chamber. Great article Dave, thanks for posting that.

 

[DaveTooley]

I did a test where I marked the ogive with a magic marker lengthwise. Then shot with the mark indexed in the same place in the chamber. Out of 10 shots, 8 comet tails came from two lands.

 

[clowdis]

This is a pretty good example of 'comet tails' on the target. A well worn first inch or so, that is somewhat larger that bullet diameter, will yield cracked jackets and molten lead leaking out as it passes through the target. My first .17 Mach IV started doing that at about 3600 rounds with about 1 in 10 bullets 'smoke trailing.' Then by 4000 rounds all bullets were doing it. I finished it off in a dog town at 4060 rounds and committed it to the trash can. When I took it off you could drop a bullet in the breech and it would stop about 2 inches past the chamber. Great article Dave, thanks for posting that.

I may be thinking wrong, but it looks like the comet tails are backwards for a right hand twist barrel. Can anyone explain what's happening here?

 

[nmkid]

Interesting, it seems the temperature of the bullet in the groove marks exceeds the melting point of lead, although very briefly. Explains why, at the range in the pits, you only pick up a freshly fired bullet once!

I believe I remember reading something about this years ago. The writer opined that it didn't matter if the tip of a lead bullet was slightly deformed because it was going to melt off way before it got to where it was going to hit.

 

[GotRDid]

Yep I did that at Perry the first time I was ever in the pits My digital thermometer can confirm that article

Same!

 

[Bill Norris]

I may be thinking wrong, but it looks like the comet tails are backwards for a right hand twist barrel. Can anyone explain what's happening here?

Maybe, but looks to me like the darkest and closest portion of the comet is closer to the bullet hole with the tail fanning to the right.

 

[gunsandgunsmithing]

Interesting! A crazy thought just went through my mind for a second...500C is 932F. Is there any chance smokeless powder in the bore could burn from both ends? Hmmm.

 

[Ned Ludd]

I may be thinking wrong, but it looks like the comet tails are backwards for a right hand twist barrel. Can anyone explain what's happening here?

Here are links to a couple more "comet tail" images"

Comet tails

What the hell are those and why do they happen? Testing a load for a 1913 M96(all matching serial#’s) Trying to replicate the original 140gr load. Powder:43.7gr of RL-22 Bullet: 142gr SMK Primer: S&B LR Case: Win 3rd firing That target is at 50yds. Don’t know what that little smear is...

forum.accurateshooter.com

Comet tails

I'm guessing the orange box will be setting some records this year after people read this? I've not had the success rate with orange box bullets as I've had with yellow. I wonder if differences core seating setups have an effect. (Preformed boat tail cores) Not enough to make me want to stretch...

forum.accurateshooter.com

The comet tails in these images go the other way, suggesting those in the image above were either from a left-hand twist barrel, or perhaps the image was reversed (mirrored) in some way during processing. Those are the only explanations I can come up with.

 

[gunsandgunsmithing]

I believe I remember reading something about this years ago. The writer opined that it didn't matter if the tip of a lead bullet was slightly deformed because it was going to melt off way before it got to where it was going to hit.

Maybe irrelevant but the plastic tips on many of today's bullets don't seem to melt away. I would think it would have a pretty low meting temp, fwiw. I've recovered those plastic tips from deer, etc, is why I say they don't appear to melt away.

 

[divingin]

Maybe irrelevant but the plastic tips on many of today's bullets don't seem to melt away. I would think it would have a pretty low meting temp, fwiw. I've recovered those plastic tips from deer, etc, is why I say they don't appear to melt away.

Many, but not all? Wasn't that exactly the reason that Hornady discontinued most of their AMAX line several years ago (the 168's are still being made)? I seem to recall they said the tips were melting downrange and affecting ballistics. They changed the plastic material or formulation and rebranded them as ELD's.

 

[gunsandgunsmithing]

Many, but not all? Wasn't that exactly the reason that Hornady discontinued most of their AMAX line several years ago (the 168's are still being made)? I seem to recall they said the tips were melting downrange and affecting ballistics. They changed the plastic material or formulation and rebranded them as ELD's.

Well, many, in that context was meant to say that many bullets use plastic tips. Don't read too much into that. You may well be right about why they discontinued and changed the material used. I simply don't know. I was only saying that I've recovered plastic tips inside of a couple of deer that were shot with plastic tipped bullets. Again, just a simple statement and don't overthink or over analyze it. I really wasn't trying to dissect the issue at all with my post. Nothing more than an observation on my part.

My previous post was a little more thought provoking, to me. According to the link Dave posted, the base of the bullet is well above the flash point of smokeless powder. That makes me wonder how there could be unburned powder left in just about any load where the base of the bullet gets above the flash point. There may be a simple explanation but that just made me think about it and I've never considered the possibility before.

 

[wkdickinson]

Interesting, it seems the temperature of the bullet in the groove marks exceeds the melting point of lead, although very briefly. Explains why, at the range in the pits, you only pick up a freshly fired bullet once!

I was pulling targets in pits at Camp Grayling, MI at a 1,000 yd match back in the late 80's. The guy I was pulling for had a low shot that went through the berm and dropped into the pits - in fact, it dropped right down inside the back of my shirt collar. That was not an experience I ever want to have again.

 

[gunsandgunsmithing]

I was pulling targets in pits at Camp Grayling, MI at a 1,000 yd match back in the late 80's. The guy I was pulling for had a low shot that went through the berm and dropped into the pits - in fact, it dropped right down inside the back of my shirt collar. That was not an experience I ever want to have again.

I bet that's right. I've spoken to a person that had been shot. He said it burned like hell. I don't remember any other details except he had been both shot and cut. He said being cut was worse.

 

[AccelR8]

I bet that's right. I've spoken to a person that had been shot. He said it burned like hell. I don't remember any other details except he had been both shot and cut. He said being cut was worse.

I'm a lucky SOB but I had a bullet pass across me from right to left at the level of the upper abdomen an inch away and graze my left forearm (I was holding a rifle with both hands). It raised an abraded purple welt on the skin and yes, burned like someone had laid a red hot iron rod on it. Just with that fraction of a second contact.

 

[gunsandgunsmithing]

I'm a lucky SOB but I had a bullet pass across me from right to left at the level of the upper abdomen an inch away and graze my left forearm (I was holding a rifle with both hands). It raised an abraded purple welt on the skin and yes, burned like someone had laid a red hot iron rod on it. Just with that fraction of a second contact.

I'd say you were VERY lucky!

 

[LCazador]

I experienced this with a 22/6mm Rem 40 degree improved cartridge back in the early 90's. That had about 700 rounds through it. Thinking the fire cracking was actually tearing through the jacket I decided to buy a Hawkeye bore scope and verify barrel condition. That was my first bore scope by the way. After a bore inspection with the Hawkeye, bingo! The firecracking was bad enough I thought to tear the jacket apart. I then tried smoothing the barrel with JB bore paste. That worked but only for a few rounds. I surmised that the smoothing probably did nothing but enlarge the bore enough to improve the jacket integrity. A new barrel took care of that problem. I also had this happen in my early years of shooting an old worn out 30/06 03/A3 and those jackets were pretty thick back then.