Lead lubed cast bullet question - How does the lube work?

[Bullseye]

I would like to understand why the lube in a groove of a bullet, being behind lead to barrel contact works.
I don't see what good the forward part of the bullet benefits from being lubed in the recessed ring as it travels down the barrel.
It would only be getting lubed on the rear part of the bullet on the travel, right?
Now I don't know much but I was guessing that maybe once a bullet is fired the lube is heated and blasted forward before the forward part of the bullet reaches the forcing cone at the rear of the barrel.
Is that what happens?
Thanks

 

[ReloaderFred]

This has been an ongoing debate for many, many years. Some believe the lube left behind by the previously fired bullet lubes the next one, and some believe the lube is squeezed by the compression of the alloy and oozes forward.

I'm in the camp of the lube from the previous bullet leaving enough lube in the bore to assist the next bullet. Some will disagree, but I've proven it to my satisfaction.

Hope this helps.

Fred

 

[anothernewb]

I think it works in the exact same way an o ring or a piston ring works. Lead is soft - even the hardest lead is softer than the barrel steel. the lube ring simply squeezes into the gaps and seals much like an O ring does. I think it's actual lubrication is behind the bullet fore end, but again without the fore end providing resistance like the piston crown, it would simply ride in front, get pushed out of the way, and be useless.

 

[clearcut]

^^ the lube is spun out by centrifugal force created by the high RPM's and left for the next round.
CC

 

[MEHavey]

While residual lube from previous bullets is a significant factor, so too (apparently) is the
hydraulically forced vapor/film flow ahead of the bullet as it travels down the bore.

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

 

[Bullseye]

hmmm. Not such a dumb question after all.
Good link info too. Thank you.

 

[ReloaderFred]

Some of the arguments don't take into consideration outside lubed bullets, similar to the current .22 Long Rifle, et.al. For many years, outside lubrication was used for handgun rounds, but was abandoned for the most part due to debris being collected by the exposed lube prior to the round being fired.

Like I said, this has been an ongoing argument for many, many years.

Hope this helps.

Fred

 

[Laphroaig]

Hmmm, never really thought about this topic much

Considering the extra smoke coming off of (some kinds) lubed bullets, I wonder if most of the residual lube gets burned off by the hot powder gasses?

Just wondering...

Laphroaig

 

[Buck13]

I think maybe a lot of the smoke comes from bullets with lube on the base. Someone made me some flat base SWCs with a nice soft lube which is sticky at room temperature. Don't know if they started like this, but after riding around in the box they have lube all over. If I wipe the bases with a paper towel before loading, I get much less smoke.

I notice little smoke from bullets with the harder, crayon-like lubes. Some people say those lubes are less effective due to being too hard. I should load up some batches in which I roll half of them on a film of Lee Alox over the crayon lube and see if I can detect less leading. I'm sure I'll see more smoke!

 

[GLOOB]

You can look at the different functions of the lube, separately.

As a lubricant, there's some left in the bore for the next shot.

As a gas seal, the lube just takes up some micro gaps that might develop due to tiny variations in the rifling and/or bore size as the bullet travels down the barrel, which is why I feel like lube has to be applied behind at least part of the driving band. The drive band in front of the lube groove is the part that is going to benefit the most from the little reservoir of gas sealant behind it; the front drive band has to prevent the lube from shooting past it, and thus it is more important for the sealing. The base needs to be full diameter and symmetric for accuracy, but little tiny gaps from an inconsistent rifling don't matter back there, so much. As long as that front band stays sealed, the little gaps in the base don't grow/melt from gas cutting, and you don't get poor accuracy and tumbling bullets.

If the bore is smooth and straight and there's no significant gas blowby, most of the lube should stay in the groove and get "shot out" with the bullet without vaporizing into smoke. Only some guns/ammo will use up all the lube in the groove. The trip down the bore heats it up, but not nearly as much as what occurs with some gas cutting. If your bore/chamber is amenable and the bullets fit, you hardly need any lube, at all. Sometimes you don't need any. Alox and hard blue lube aren't terribly special, IME. They're smokey sometimes, and they're practically smoke-free, sometimes. It depends on the gun and ammo, and in the case of Alox, it might depend on the amount that has to be applied, I suppose.

 

[Missionary]

Greetings
It is easy to establish that the lube from the previous rounds help the following cast bullets on their journey down through the lands and grooves.
Just have to thoroughly clean after every shot. Depending on the bullets base pressure, the amount of friction the bullet has in the barrel plus barrel condition, length and rifling twist and depth, it does not take hundreds of fired rounds in that every shot cleaned barrel to convince the shooter it is best not to clean a good cast bullet barrel.
Yep I tried it in a very accurate Interarms Mark X 30-06. Within 5 rounds I was convinced I had erred and the lead smears were for real.
With some of the high tech super slick bullets lubes that micro coat the pores possibly cleaning certain ultra smooth barrels would not matter. But I am one of those who just does not go out of his way to fix that which is not broken.
Since I seldom clean my rifles until they exibit worsening accuracy. Black powder is another story. Just depends on the load in that particular barrel how often it gets some wet patches pushed through.
Mike in Peru