Temperature of fired bullet?

[Ray B]

Just wondering if there is an instrument available that could read the temperature of a bullet as it left the bore of the rifle. the reason that I ask is: several years ago I was experimenting with loading bullets to higher than designed velocities. the one that really got my attention was a 60 grain Hornady .257" flat nose bullet designed for a 25-20. I loaded some in 257 Weatherby cases. I forget the charge. there was a target at 100 yards. I fired one over a Chrony chronograph. On firing there was a brief grey streak in line with the line the bullet would have travelled. The Chron registered 4505 fps. The case showed no sign of high pressure. Walked to the target. No sign of any hit. Walking back to the firing line I saw no sign of any part of the bullet. It just disappeared. I figured the spin- 1-10" caused 5400 rps which overwhelmed the thin jacket and the bullet just disintegrated. but in wondering about the situation I've wondered what the temperature of the bullet would have been as it exited the rifle. Secondly, if it was quite hot from the friction , pressure and powder heat, what effect would that have on bullet performance as it hit a game animal. Could bullets that hit an animal while the lead in the bullet is above the melting point cause "failure" to perform?

So just wondering- is there a thermometer available that could register the temperature of a fleeting bullet?

 

[Randy F]

Sheeesh! I don’t know of a thermometer to measure it in flight but I think had you fired a second shot right away it would’ve dripped into a cup for you to check it.

 

[Alistair]

Hornady did a white paper on this regarding their ELDx bullets.

Link: https://www.hornady.com/assets/site/hornady/files/resources/ELD-X_ELD-Match_Technical_Details.pdf

Their conclusion was that heating within the barrel itself is not that significant because whilst there's a lot of friction and pressure there, the bullet has enough thermal mass to soak up the heat without warming significantly over the tiny amount of time it's in the barrel.

However, they also found that aerodynamic drag during flight does significantly heat the bullet (there's enough time relatively speaking to warm it up and lots and lots of air resistance, plus shock wave effects as it's supersonic). They suggest that the tip of a bullet at 3000fps is experiencing temperatures of around 850F, enough to heat the tip to high enough temperatures (300F+) to effectively melt polymer tips. Hence their 'heat shield' tips on the ELDX which retain their shape at up to 700F. No mention on what the overall projectile temperatures are, though one would assume they're significantly lower away from the tip area.

Figure 3 describes the stagnation temps for various velocities experienced by bullets in flight at various velocities. An interesting piece of work, whatever you think of the ELDX design itself.

 

[Woodcarver]

My former boss and I bought 2000 45gr HP Dogtown bullets a few years ago. I was loading them in a .223, he was going to use them in a 220 Swift at 4500fps+-. I was getting poor groups, around 2"+ usually. He was lucky to hit paper at 50yds, almost rare at 100, and a lot of the holes were keyholes.
Did a little research and found out that bullet was designed for velocities under 3000fps. Reduced my 223 load accordingly and get nice 3/8"-3/4" groups from 3 different barrels. He made me buy his half of the box, lol.
In answer to the question, I've not heard of a thermometer for measuring bullet temp. But if you try a bigger target, you might find you have the same issue with that 60gr .257 bullet at that kind of velocity as my boss did with the round nose HP 22.

 

[mark-hunter]

A guy I know, was experimeting with new type of partial-monolithic bullet Grom, by PPU.
He fired it in the wet paper stuck to check terminal ballistic.
After a shot, he was not able to hold it in a hand, how hot it was.
Tried with other, (some soft point), and soft point when fired was normal temp, easy to hold in hand when collecting from paper
This is one thing that I picked up, for other details, I have no idea.

 

[Challer]

You’ll be better off measuring the temps of the bullets you capture after firing. I’m not sure of the value of this measurement.

 

[oldfart009]

There's probably a fair amount of heat imparted on the rear of the bullet, simply from the the combustion of the propellant.

There's a certain amount of heat imparted to the outer skin of the bullet due to air resistance.

There might even be some burning at the entry point of a bullet, but there is so much other destruction taking place, it probably is insignificant.

Also since the bullet is moving, and dissipating heat over the wound channel and slowing down, it probably doesn't have a lot of time to produce burns.

The wound channel is probably larger than the radius that the heat could affect.

 

[BourbonTrail]

In a past life, I’ve measured it using telemetry, but not on regular bullets. High speed infrared camera won’t be 100% accurate (heat reflection off of the metal and gases), but you can get close…if you want to spend that much.

Flight friction (like in the white paper above) is definitely an issue on bullet leading edge (nose) above a certain speed. 3000fps is roughly Mach 2.7 at sea level (according to WP results in 850degF LE temp). Above Mach 1 induces friction heating, above Mach 5 (5500fps) results in about 1600degF LE temperatures. Food for thought.