Asphalt?

[Ricochet]

Something else I've thought up lately: Has anyone tried asphalt (like military loads often use to seal the bullet in the case neck) as a boolit lube? I'm thinking that the real purpose(s) of lube isn't so much to lubricate the boolit's passage down the bore as to seal gas blowby, particularly as the boolit is swaged into the rifling, and secondarily serves as an "antiflux" to keep lead from sticking to the barrel steel. Although asphalt isn't very slick, it would seem likely to serve the sealing function well, and I've certainly never seen it used as a soldering flux. Unlike waxes, which are solid or gummy at low temperatures, then suddenly melt to a thin watery consistency, asphalt is hard when really cold, gummy at "normal" temperatures, slowly becomes more fluid as it's heated and has to get really hot to become runny and thin. Better characteristics for sealing fiery hot gases, I'd think. We all have some experience with shooting jacketed bullets down bores with this stuff smeared on their bearing surfaces, and it doesn't seem to cause undue fouling.

Just wondering...

[felix]

Asphalt is too stiff as a lube. Prolly OK in a real machine gun after the barrel is close to melting. Consider the amount of time the heat is applied to the lube when the round is shot. ... felix

[StarMetal]

Asphalts are highly complex and not well-characterized materials containing saturated and unsaturated aliphatic and aromatic compounds with up to 150 carbon atoms. Their composition varies depending on the source of crude oil. Many of the compounds contain oxygen, nitrogen, sulfur, and other heteroatoms. Asphalt typically contains about 80% by weight of carbon; around 10% hydrogen; up to 6% sulfur; small amounts of oxygen and nitrogen; and trace amounts of metals such as iron, nickel, and vanadium. The molecular weights of the constituent compounds range from several hundred to many thousands.
The compounds are classified as asphaltenes or maltenes according to their solubility in hexane or heptane. Asphaltenes are high molecular weight species that are insoluble in these solvents, whereas maltenes have lower molecular weights and are soluble. Asphalts normally contain between 5 and 25% by weight of asphaltenes and may be regarded as colloids of asphaltene micelles dispersed in maltenes.
Many of the compounds in asphalt are polar since they contain alcohol, carboxyl, phenolic, amine, thiol, and other functional groups. As a result of this polarity, the molecules self-assemble to form multimolecular clusters with molecular weights up to 100,000. The adhesion of asphalt to aggregate is also thought to depend on the polar attraction between molecules in asphalt and the polar surfaces of aggregates.
"Asphalt has a polymer-type network that is unique," Usmani says. Although not a polymer in the strict sense of the word, it is a thermoplastic material--it softens when heated and hardens upon cooling. Within a certain temperature range an asphalt is also viscoelastic, which means that it exhibits the mechanical characteristics of viscous flow and elastic deformation.



I don't think I want it in my barrel as a lube.




Joe

[Ricochet]

Perhaps asphalt blended with soft wax (like toilet sealing ring), Vaseline or cosmoline? Or with a little oil?

[Bass Ackward]

Obturation forces from pressure are hard to visualize, but every bullet feels it in the form of the base trying to pass the nose. It's hard to imagine that the purpose of lube is to seal when the problem with a lube failure is that it wasn't strong enough in viscosity to control the obturation on the base of the bullet causing it to lead. All that pressure was doing was making a better seal.

[StarMetal]

Bass,

Think of in sealing as BarSto or STopLeak, in that it seals the imperfection on the bullet. It plugs these gas escape holes. I feel it seals and lubes both, not just seals.

Joe

[Ricochet]

Yeah, probably does both. But I don't think the most problematic leading always comes from simply rubbing off lead frictionally, with or without obturation. I think it comes from leaking gas melting away lead where it flows through a narrow channel between the boolit and barrel steel. The high temperature, high velocity gas flowing through such a channel doesn't allow a stagnated, insulating boundary layer to form as it does on the exposed base of a boolit, where the gas is not moving rapidly relative to the boolit surface. So the gas jet melts away a thin layer of lead, which sprays ahead of the driving band and deposits on the bore wall, much as flame spraying is done with a torch. If it weren't so, we wouldn't see the seeming paradox of a very hard, nonobturating boolit undersized for a bore leading badly, with a softer boolit of larger diameter curing the leading. The softer, larger boolit more effectively seals the gas, that melts the alloy of the smaller, harder boolit as it leaks by at high speed through the leakage channels.

Too soft a boolit, or one that picks up a lot of speed running down freebore before engaging the rifling, can strip in the rifling and open up passages for blowby that cause this flame spraying. I've seen revolver boolits strip the full width of the lands on the front band. It's got to engage the rifling tightly, without stripping, for a good seal.

A viscous fluid lube that squishes in (and out of) the lube grooves as the boolit enters the rifling will help by flowing into and plugging the small channels around the boolit, and if it's not solidly stuck to the bottom of the grooves but slings outward and rides against the bore wall due to centrifugal force, it will be in better position to block forward flow of gas behind the boolit. Keeps it sealing as it goes on down the bore, after the initial displacement as the boolit swages into the rifling. It's got to be soft enough to turn loose evenly all the way around the circumference so it doesn't unbalance the boolit at muzzle exit. (That's where you get your "lube star.")

That's why I think a lube's at least partly failed if I still see the grooves full of it when I dig it out of the backstop. That space might better have been occupied by more lead instead of a bunch of pretty colored, expensive hard wax that sat there and went along for the ride. Lube works when it's out at the periphery, in contact with the bore wall.

That's my theory about it, anyway.

[felix]

Theory? Nope. Fact. If softer lube does not work (like in cold weather) you must protect the base of the boolit further. Something that will take on heat quickly, like a large sized (in diameter) slice of polyethylene. Let the boolit push the ablator down into the neck, but make sure the ablator does not drop into the powder space. ... felix

[StarMetal]

John,

I doubt there are many people that are/were fascinated with finding a bullet and examining the rifling marks on it then me. Even since I was a child till present. It's just something that has fascinated me. So I've examined alot of fire bullets and in that time I've found some that were gas cut. Mostly pistol/revolver bullets. All bullets have one lube groove and of course some have more. The gas cutting always starts at the rear of the bullet simply because that's where the hot gases originate from. Never have I found a bullet where the gas cut through the rearmost driveband and on through the lube groove to cut the next driveband, or if the next was the last driveband, exit in front and ahead of the bullet. I'm not sure either if the cuts I found were melted cuts or just pressure cuts. I'm not convinced on your theory. I do think that lube was intended to rub on the bore and grooves, not become a liquid and coat it. I'm not sure that they can become a liquid become the time they are exposed to heat is very very short.

Lubes, wads, gaschecks, etc., have been debated and tried since the creation of firearms and I think, will continue to go on for quite some time. I've tried alot of the polyethylene base wads in revolver loads and didn't notice much of a change. The biggest change I've noticed in revolver loads is kapok, it absolutey keeps the cylinder, the cylinder face, and the frame forcing cone area much cleaner then when not used.

Joe

[robertbank]

Just my two centsCdn but I don't think much of the gas cut theory, frankly. Now I realize there are relatively high pressures involved here but the base of the bullet is exposed to the heat and pressure for such a short time (For my .45acp about 1/72 thou of a second) I just can't believe any gas cutting takes place at all. When I have had leading it was always in the first 1/2" of the barrel and since going to a soft lube that has virtually stopped entirely.

My conclusion for .02 cents Cdn, most leading in handguns comes from lead smearing off the bullet as the bullet enters the rifling. The grooves in my 9MM are much more deeper and agressive than in my .45acp and I have never experienced leading in my 9MM as long as I keep veloicities within reason. I caveat that statement in that for awhile I was sizing my 9MM bullets .355 which was dumb on my part and some leading did occur as well as tumbling of course. I attributed the leading to the bullet bouncing around as it passed down the barrel and not to gas cutting.

Take Care

Bob

[felix]

Don't like kapok? Use a very, very slow powder for filler. ... felix

[StarMetal]

Used Kapok for over 20 years felix...great stuff is used right.

Joe