One of the gun-handling rules I mention in my range safety briefings is to avoid unnecessary exposure to lead because it’s a toxic substance.

“But lead’s only inside the bullets—right?”

Well, no, it’s all over the place, and mostly (but not entirely) comes out of the bullets when they’re fired. It’s seldom as obvious as here, but these illustrate the effect:

Interesting. What bullet and distance to target?

The ammunition was 124 grain FMJ (unknown brand of bullet) 9mm in commercial reloads fired from an S&W M&P of some flavor. The phenomenon showed up with shots from about 4 feet to 6-7 feet.

The small dents in the paper were caused by unburned powder particles.

Pure speculation, but I would bet plated bullets not FMJ, and the rifling cut through the plating.

A bigger question, it seems is why is the exposed lead so unstable that it is shedding at that high a rate?

Are these bullets by any chance frangible?

A quick internet search suggests that unjacketed lead bullets begin to disintegrate from rotational forces in the 120,000 to 140,000 rpm range. A 9mm with a 1 in 10 twist at 1050 fps is spinning 75,600 rpm, well below suggested disintegration speeds.

Again, a guess... it could also be that the rifling, once it cuts through the jacket, is galling or abrading the lead core leaving lead dust or particles which are then shed in the first few feet, which is why you are seeing this effect at close range, but not at the longer targets.

Very interesting stuff.

It may be the blowby of burnt propellant being NO2, CO, CO2 H2O and enough "moisture" to carry the burnt/unburnt solids to the target, and not be as much lead as it appears.

If there is a chemical lab or even a university you might ask if someone wants to do a paper on your paper.

Someone might need a bump in a grade.

I too suspect that those spirals are powder resides rather than lead.

That first one looks kindof shiny like lead would be - not like burned or un-burned residue...

I do suppose it's all a guess unless other evidence is available.

Thanks for the comments. I do not believe, though, that the gray deposits were made by unburned powder.

I have seen unburned powder patterns countless times because one of my agency’s handgun qualification courses requires firing from close distances (3-4 feet), and depending upon the loads significant unburned powder hits the target and leaves very obvious patterns. They never look like spirals. They’re more diffuse and circular like a shotgun pattern. The imprints the powder granules make are visible in the above photos, especially the second one.

I don’t know of a mechanism that would cause unburned powder to be deposited in such tight, well-defined spirals. If, however, lead were being extruded from point sources on the bases of the bullets, that’s exactly what we would expect to see. The patterns start large and far from the bullet hole, but become tighter and denser close to the holes.

Perhaps most conclusive are the similar gray deposits pictured below. Both show holes in witness paper made by 5.56/223 bullets after they passed through the double bed wall of a 1976 pickup.

The first shows the hole made by an M193 (55 grain FMJ) bullet, and the second was made by a 75 grain Hornady Law Enforcement TAP bullet. The M193 had evidently become deformed to a larger diameter by punching through the metal, and that would account for lead’s being extruded from the base. The TAP bullet had started to tumble and disintegrate, but the swirl pattern is still somewhat visible. Both bullets were fired a distance of 15-20 yards, and as I say, through the double wall of a pickup bed. There was therefore no way that the deposits could have been made by unburned powder.





I no longer have any of the ammunition to inspect, but I know the bullets were not frangible, and I believe they were conventional jacketed FMJ, and not plated; not certain about the last, though.

Full metal jacket is not total metal jacket. The base of those may have been exposed lead.

I agree with sigfreund that he is seeing lead from the bullet on paper. I also agree that there is no mechanism for burnt power to have a coaxial rotation matching that of the bullet after it leaves the barrel.

I think those bullets must either have been plated or have a very thin jacket. I have recovered some 45 ACP bullets that I fired into the ground and the grooves were pronounced but the lead core was not exposed. As detroit mentioned the base of the bullet could also have been exposed lead.

In flight the tip will be heated due to air friction but I doubt it would be hot enough to melt lead. We do know it's hot enough to melt certain polymer tips as Hornady has shown us. The grooves of a bullet will be superheated early in flight due to the high friction at those localized areas. I did a search and found a FLIR image that confirmed this.

The website below shows a FLIR image of a .30 cal rifle bullet just after leaving the muzzle with a tip temp of 170C, a rifling groove temp of 320C, and a tail temp of 500C. Lead typically melts at 320C (depending on alloy of course).

A pistol bullet may not reach these temps since it has a much lower muzzle velocity, but based on the temp gradients shown in that IR image it's certainly in the realm of possible that the bullet is shedding some superheated lead in localized exposed areas during part of it's flight.

http://www.advancedimagingpro....d=1&id=180&pageNum=1

And here are some videos from FLIR. They start testing right around 3:28 in the first vid. If you pause them just right you can see the glowing hot bullet and shotgun pattern powder residue right as they leave the muzzle. Obviously no temperature scale bars on these but it's still neat for visualization.

Thanks sigfreund for the fun topic.

Thanks for the videos. Very informative.

Interesting.

Thinking out loud here...

The spiral would have to be induced by the spin. The source seems to be coming only from a small number of sources (one or two, in most of the photos) vs. coming from all surfaces uniformly, in which case it would be a more or less radially uniform grey zone vs. a defined one or two arm grey spiral.

Guessing it may have to do with how the bullet interacts with barrel rifling? But if so, not all grooves are having an equal effect (one or two spiral arms compared to the number of grooves in a rifled barrel.)

Or maybe the bullets are not identical and the plating/jacketing is not identically deep on all sides?

The plated bullets I’ve seen have had a distinctive appearance in that they’re not as smooth and shiny as normal jacketed bullets. I therefore don’t believe the ones that caused the effects above were plated, but I’ll have to check again to see if I have any available to examine closer.

The only other guns I’ve personally seen that ammunition fired from were SIGs and Glocks. I checked an M&P chambered for 40 S&W and noticed that it has higher lands in the rifling than the SIG pistols I’m familiar with, and of course Glocks don’t have lands and grooves at all. Even if the bullets were not plated, it’s possible that the jackets were thinner than normal and perhaps the deeper rifling of the M&P could have cut through some of them.

quote:

Originally posted by joel9507:
Interesting.

Thinking out loud here...

The spiral would have to be induced by the spin. The source seems to be coming only from a small number of sources (one or two, in most of the photos) vs. coming from all surfaces uniformly, in which case it would be a more or less radially uniform grey zone vs. a defined one or two arm grey spiral.

Guessing it may have to do with how the bullet interacts with barrel rifling? But if so, not all grooves are having an equal effect (one or two spiral arms compared to the number of grooves in a rifled barrel.)

Or maybe the bullets are not identical and the plating/jacketing is not identically deep on all sides?

Sound reasoning.

Yep, I am convinced after seeing more information on this.

quote:

Originally posted by detroit192:
Full metal jacket is not total metal jacket. The base of those may have been exposed lead.

Right you are...

Sigfruend, you stated some (or all?) of these passed through the bed wall of a pickup?
Could that contact have shaved off enough of the copper jacket to get to the lead core?
I’m also in concurrence with detroit192 about FMJ vs. TMJ bullets.

quote:

Originally posted by hudr:
Sigfruend, you stated some (or all?) of these passed through the bed wall of a pickup?

Only the two 223/5.56 bullets. The first three photos above are of holes made by 9mm bullets fired from 4 to about 6 or 7 feet with no intermediate barriers.

I think we are over thinking it. Temp when fired would be nice to have, but pure specu makes me think it is something stripping any jacket off, and the spread from the bullet impacting the paper. Burned powder will not travel in the spiral, but spinning lead from the actual bullet will.