Head scratcher: How does lube work?

[catboat]

I've been asking myself this question, and I'm not sure if I'm any further ahead as a result. It at least passes the time while I'm driving.

I've read that bullet lubes (and lube grooves) get "shoved back" or "Squeezed out" of the bullet grooves due to the extremely fast acceleration upon powder ignition. I have read that lube grooves on bullets may have some benefit to not be square in cross section, but angled back ("V shape" to some degree) or round, to facilitate the "the lube squeeze" out upon "detonation acceleration."

Here's why I started to think more to it. Upon powder ignition, gases expand and the bullet accelerates forward. Does any of the lube get "pushed forward" by the gas (as in gas blow by / gas cutting) that would lube forward?

I look at various bullet designs and wonder how they work. First, is a "true Keith" bullet. Square lube grooves, and 3 equal groove-deep bands. The lube goove is behind two of the leading bands. In essence, you are only lubing the last 1/3 of the bullet. What is lubing the first two bands? Why no leading? Is this due to "gas push forward" or "gas cutting" lubing? I don't know.

Then I looked at some cast bullet designs (I'm playing with some online designs at Mountain Moulds for a 9.3/.366" ~ 250 - 300 grain gas check bullet for my 9.3x62). I has a short neck (as does the 35 Rem, and 300 Savage which I also have). How do you have a large bore riding surface, and avoid leading?

So I ask the distinguished readers of castboolits.com to shed their views. Just how in the world does lubing work? If you can NOT lube for 2//3 of a Keith bullet, and only lube the bottom third of the bullet, there must be some other factor involved. Maybe there is something to a tumble lubed bullet.

If the only factor in lubing was the "acceleration squeeze out" factor, you'd think a lube groove pattern that has WIDER grooves up near the crimping groove, and then narrower lube grooves as you get toward the base of the bullet would make the most sense.

Enlighten me.

Thanks in advance.

[jonk]

Dunno, but it doesn't all get thrown out- I've recovered bullets from the dirt with plenty of lube still in the grooves.

[chevyiron420]

i have always kinda thought that the first boolit gets down a cold barrel with some luck and leaves some lube behind it, then each boolit after that gets the lube from the one before it. probably wrong, i dont know, but i dont get the LLA at all. i have 200 boolits for my 44 lubed up with LLA drieng now and have no confidence in them at all. im going to tumble them a second time today for good measure.-phil

[4060MAY]

this is one of the few explainations that makes sense

http://www.lasc.us/FryxellLubeCastBullets.htm

[Blammer]

good read!

[9.3X62AL]

I have likened the action of boolit lube to that of motor oil in a car engine--that it serves as a bearing surface friction shield, and to assist in sealing the propellant gases behind the boolit base and drive bands. Think of the drive bands as piston rings, and the barrel as a cylinder.

Regarding your 9.3 x 62 boolit project, my rifle is a CZ-550, and its throat showed roughly .300" of leade clearance before rifling began. I used the MM software to slightly tweak the .366" 270 grain "default" pattern on Dan's program, which derives from a design produced by "Eirik" on Accuratereloading.com. I took the caliber's neck length + leade clearance and created a driving body of .600". The resulting boolit shoots 1.125" to 1.25" 3-shot groups at 100 yards, 23.0 grains of 2400 giving 1750 FPS, and has no part of the boolit base protruding into the powder space.

[Freightman]

I use teflon tape on my 45/70 wraped to the top of the lube grove and shoot it with a 450g Lee FNGC boolit have never had any leading. My point there is no liquid to pump, so how does that figure in the pumping theory? The 450 g boolit crno's at 1480+ fps. I also use LLA with no leading and 50/50 bees wax and LLA no leading. I have used the teflon on 8MM 308 311 with the same results (a little harder to wrap) but no leading.
How does lube work? I do not know but will worry about it when it doesn't work.
Printed off the artical and put it in my note book, knowledge is worth saving for future study. Thanks for the link

[arkypete]

That's one of those questions that reminds me of a joke.
Seems that one of the major networks wanted to find out what the common people were thinking, so they sent thier best story finder out to the hinterlands.
So this hotshot walks up to a county fella and asks 'What's the most interesting invention of the 20th century?'
Well the country fella ponders and ponders, then answers 'The thermos!'
'The thermos ?' says the hotshot.
'Yup!' replied the country fella.
This really intriques the hotshot and he asks 'How So ?'
'Well says the country fella "The thermos keeps hot things hot and cold things cold.'
'Sure does' says the hotshot.
The country fella continues "How do it know?'

Jim

[Bass Ackward]

I have been thinking on this since the last major discussion we had over lube. I have always destroyed the theories of others when examples could be produced, but never offered one of my own. You have to realize that there many different firing scenarios from shooting bore sized, gas checked bullets in a handgun to a throat choked rifle bullet that is sealed from gas at the get go. Complete seals can be established to none at all. And any lube theory must stand up to explain all situations. There are usually two theory camps. The hand gunners who tend to be Lube Sealers or Lube Pumpers. Or the rifleman and Lube Lubricators or Hydrologists of which I was one. Neither camp is correct.

So here comes my NEW and UPDATED rational.

1. I know that lead has a poor heat transfer rate which is the reason that surface friction can cause melting and thus leading.

2. I know that all lead that comes in contact with a bore will encounter frictional forces from either pressure, acceleration or rotation that will cause heat. Unless prevented, friction will eventually cause enough heat to cause melting described in 1. above.

3. I know that all lubes, no matter what they are made of, melt under heat. No matter how hard they are, this melting turns them or portions of them into a liquid state. There are three properties of liquids that apply here. A: All liquids can NOT be compressed by any force known to man. B: All liquids expand when heated. C: All liquids transfer heat very rapidly like dunking a hot iron in water or oil.

4. The slipperier a lube is, the less friction (heat) will occur under every possible firing scenario.

5. The harder a bullet is, the less friction from deformation or obturation will occur. As a side note: the harder a bullet is, the more spring back it will have to maintain contact over distances of dimensional imperfections that is within the bullet's ability to expand.

6. The smoother and more dimensionally correct a bore is or becomes over it's life, the less friction (heat) it will generate and the better seals it will maintain. Therefore, a smooth and dimensionally correct barrel allows the use of weaker lubes or softer lead at the same pressures or higher pressures and velocities with harder lead than it did before.

These are the factors we work with or around when we work with cast. Paper patching or taping prevent heat transfer from metal to metal contact, so less friction (heat transfer) means less need for lube or none at all.

Here it is: THE PRIMARY PURPOSE OF A LUBE IS TO WISK AWAY HEAT FROM METAL SURFACES. How much lube is needed is that amount or quality to handle the heat created by your firing situation. If barrel heat is suddenly raised, then more lube or higher viscosity lube will be required to prevent leading. The same load in freezing conditions might get away with half the lube or a less persistent lube. Yep. There it is in a nut shell. Lube isn't just a lubricator. Lube isn't just a sealer. Lube is a heat sink!!!

A second benefit of lube can be to hydraulically maintain bullet shape if in sufficient quantity to prevent friction from obturation. The larger the quantity that can be trapped, the greater the heat transfer capability. (A thimble full boils faster than a big pot) This hydraulic condition would be impossible to maintain in handguns with all the failures of bullet support and seals that occur at the B/C gap, Then pumping of the remaining lube will be the only hope. But hydraulics can be maintained under rifle like conditions. Thus rifle like conditions allow higher pressures and velocities with the same lubes and hardness used in a handgun situation.

And the third purpose for a lube is obviously to cut friction and therefore minimize the amount of heat that needs to be transferred or whisked away from the lead AND the barrel steel.

I think this .... combined theory explains why lubes or materials that are not even thought of as lubricants, like LLA, can function under certain situations. And it explains how important bore condition is to this balanced equation. It also explains why these non-lubes CAN fail before other lubes, if ideal bore conditions break down. It all depends on the firing conditions. A lube works, or it fails.

Non-lubricating lubes can perform the primary function which is to liquefy and absorb heat. And under certain conditions of smaller micro bands, they can maintain some hydraulic integrity. Understand they don't have to perform as much hydraulically because surface lubes (LLA) are generally used on stronger bullet designs. (Those WITHOUT deep, weakening, lube grooves.) When these type lubes fail, it is because they provided less lubrication to minimize bore friction and were used up by thermal breakdown before the bullet exited. (Ever hear that LLA smokes heavily under pressure?)

So as long as bore condition and dimensions and lead hardness and bullet design and controlled pressure (what ever level that is) and temperature both of the barrel and externally, can be controlled by the .... heat transfer rate of ANY lube, it works, and leading is prevented. When one or more of these factors are over come, and the lube cannot control friction, or dissipate the heat before the bullet exits, the lead is melted and left in the bore.

Expansion of lube from heat will eventually turn it into a gaseous state itself which I'll call thermal breakdown. This can explain why ANY lube smokes under pressures (that are extreme for it) just before it fails. When lube is left in the bore, the affect is additive and available to the next bullet to prevent friction, and thus heat, which is why some lubes don't perform well until a build up or a blackbore condition is established. This also explains why we need less lube in the winter as temps drop and heat is less of a factor. And why Felix always talks of viscosity or lubricity for the pressure application under which the will be used.

Well, it's hanging out now! Bed time after this.

[buck1]

I'm sold! Great post Bass !.....Buck

[357maximum]

Bass

did that hurt?

[9.3X62AL]

Bass--

Your post makes a LOT of empirical sense. If what you say here ever turns out to not be true, it still oughta be.

[carpetman]

Bass--I agree with a lot of what you say. I don't buy lead melting in the barrel as it's just not there long enough. If it would melt lead during that very brief period--it would melt the lube and a bullet spinning as fast as it does this liguid lube would be flung off,more so than a dog shaking off water and there would be no trace of lube to be found on a recovered bullet. But the inverse happens. Lube is still on the recovered bullet most of time in same shape as when applied.

[joeb33050]

Cast bullets that are small for the barrel will lead, lube doesn't help. Shoot 30 caliber lead bullets in 30/40 cases in a 40-1 7/8" Sharps while case forming if you want to see some lead in a barrel.
Cast bullets that are large for the barrel won't lead. It requires an extreme load to get .312" cast bullets to lead in a 30 caliber rifle. Big bullets almost always shoot in any gun, smaller bullets sometimes shoot.
Cast bullets with no lubricant will not lead with Cream of Wheat filling the case from powder to bullet base. No lead, none.
Norm Johnson shoots unlubricated cast bullets in revolvers, without leading, as his normal loads. Not experiments, every day shooting. He says it's all about dimensions of the bullet and the gun.
I shoot bullets with no grease grooves but with Darr lube or LLA, and no leading, so it doesn't required grease grooves to shoot without leading.
Most recovered cast bullets that I've seen have most of the lube still in the grooves.

I don't know what lube does on a cast bullet. I suspect that it does more sealing than greasing.
joe brennan

[arkypete]

I don't know what lube does on a cast bullet. I suspect that it does more sealing than greasing.
joe brennan

Joe
I'm with you.
I've thought that if I could inject nylon, some sort of plastic into the grooves of a bullet I would achive the same effect as the various greases and waxes.
Something like the rings on a piston.
Jim

[Whitespider]

This whole discussion reminds me of a theory my boss has. I work in wireless communications. What that means is, I climb communication towers to install and/or maintain radio equipment. Over the last few years, radios and antennas have become smaller and very sophisticated. Sometimes, when a new product appears, we’ll look at it and question, “How can that work?” My boss always says, “It works on the FM theory”.
Now, understand that we DON’T work with FM band radios, we use microwave high frequency equipment. Well, after several years of hearing about the “FM Theory”, I finally got up enough nerve to ask him what the “FM Theory” was.

He looks me square in the eye, smiled and said, “It’s a F@#king Miracle!”

[Maven]

Bass, et al,

"A second benefit of lube can be to hydraulically maintain bullet shape if in sufficient quantity to prevent friction from obturation."

Is this also why a CB with all its lube grooves filled (with lube of course!) can be substantially resized without deformation and loss of performance? Elongation, yes, but as long as the sizing die v. ram v. press (Lee push-through sizing dies) relationship is concentric (co-axial?) there's not much deformation. Buckshot first tried this with excellent results. I repeated it with the same effect.

[9.3X62AL]

FM Theory--too funny.

Joe, I think you summed up my take on the matter in your final sentence pretty succinctly.

[Bass Ackward]

Paul,

Of coarse. A bore is nothing more than an elongated sizer.

All,

I just feel that things, like shooting, like lube, can not be explained entirely. I doubt that they ever will be because just like there are no fact to shooting, there are no set conditions to define what a lube must do. You have to be able to visualize many different scenarios and put them all together. And you can still find contradictions.

My point was that people who believe in sealing are confused. There are bazillions of examples that counter that one that I am amazed it still has any followers. Same with the lubricator theory. Just look what normal seasonal weather does to those theories. In the cold, you don't need as much lube to seal? If sealing explained everything, then the same amount of "sealant" would be required year round. And using too much sealant would not have negative effects to cause sealant fliers. The only thing that changed was temperature levels and how much heat needed to be whisked away.

And Joe, the first shot in a clean barrel should seal just as well as the rest. Therefore, there would be no need to have a "Fouling Shot". So a whole magazine is improperly named if the sealer theory is true. And one sealant that seals, should be as good as the next, so we all should need just one kind.

Nope, no one theory can stand alone. But a combination of all three liquid properties, seal, lubrication, and heat sink, goes the farthest I have seen to explain things.

Hope it gets some minds to thinking but doesn't cause catboat to veer off the road. .

[Glen]

Heat transfer theory, huh? I'm not sure I buy that one. Ignoring the kinetics of heat transfer for the moment, let's just look at the components of the system -- the bullet, the barrel and the lube. The mass (and heat capacity) of the barrel, as well as the mass (and heat capacity) of the bullet so significantly outweigh the miniscule mass (and heat capacity) of the lube that it's just not a horse race. If the heat transfer model were accurate, then the lube would have to soak up so much heat that it would likely vaporize at the muzzle. I've recovered too many fired cast bullets that stil had lube in their grooves to place much faith in this theory.

The lead that gets deposited on a bore does not get there from melting. It gets there from ablation (also called gas-cutting).

I agree with you that one theory alone does not explain how lube works, but that doesn't mean that lube doesn't help to seal the gases in a cast bullet load.