Why are lead bullet lubricated

[ovenpaa]

On the subject of Moly coating and barrel conditioning the 22C is swabbed with methylated spirits at the end of each shoot and nothing more until it reached 100 rounds, at that point it is copper stripped with C2R and usually takes around 3 moly coated rounds to bring it back on form which is typically .150 - .180MOA in the tunnel at 100m.

The powder load is 42.1 grains of a H4831SC, removing the moly puts it over 1000m/sec at 21C and reducing the powder charge impacts accuracy, in fact it opens to .240-.270MOA at 100m. The bottom line is moly works for this rifle with its current barrel, brass, primer, powder, bullet combination.

[dromia]

For what it is worth here is my take on it.

I have shot near pure lead bullets from rifles and single shot pistols with out lube and without leading, revolvers with the gap 'tween cylinder and forcing cone are a different kettle of fish.

The reason I did this test was because we shoot smoothbore muskets with a bare ball, poor fit and no appreciable leading, yes I appreciate that the bearing surface is minimal and contact points are relatively few but still leading isn't noticeably present in these circumstances.

So from my experience bare bullets can be shot, other than from revolvers however contemporary cap and ball revolvers like the colt made no mention of lubrication and it wasn't deemed necessary and it wasn't a problem also keep in mind that the majority of ammunition shot through these guns would have been prepackaged paper cartridges with conical bullets which have a greater bearing surface than round ball.

I think that most leading doesn't come from friction tween the bullet and barrel but due to gas cutting of propellant gasses passing over the surface of a poorly fitting bullet, a properly fitting bullet won't allow gas cutting.

One of the most accurate high pressure BP rifles of its day was the Whitworth with its mecahnically fitting unlubed hexagonal bullet, minies were lubed but again this was to control the BP fouling not to stop leading which was rarely and issue.

The other factor that I think contributes to leading is the brittleness of the alloy, lead alloyed with antimony, tin and arsenic are very common mainly as the predominate source for cast bullet alloy was wheel weights which are unfortunately no longer suitable, this gave a harder but also more importantly a more brittle alloy which is prone to cracking and shearing when the bullet engages the rifling thus making a rough surface for gas cutting to take place.

In these circumstances some lube can help not as a lubricant per se but as it flows into these cracks it can "lubricate" the gas cut "spray" thus reducing its tendency to stick/lead also coating the barrel to reduce the "spray" sticking.

The other thing that lube can help with is when you are shooting cast through a less than smooth barrel the cavities/pits in the barrel which can also allow gas cutting.

As I like to use low or zero antimony bearing alloys in bullets that are carefully made to fit the gun in my case lubrication to stop leading isn't absolutely necessary.

So why do I lubricate my cast bullets? The first reason is as an insurance against gas cutting in the event of a less than perfect bullet getting past by quality control checks, it only takes one to foul and then fouling begets fouling.

The main reason I lube however is to help with retaining the shape and concentricity of the bullet, lead bullets are soft and are very vulnerable to deformation during the time they leave the case to when they are fully supported in the rifling. This is the critical stage where the bullet can be deformed, I think that the hydraulic properties of the lube helps keep the bullet in shape a bit like a shock absorber and helps the bullet resist deformation so long as their is good bullet fit without gas passing round the bullet which would purge the lube down the barrel ahead of the bullet which in this case would help stop the "spray" leading the barrel but do nothing to help the bullet keep its shape.

I am no scientist and this is only my take on it after 4 decades of observation of the subject.

This is a very complicated subject due to the many variables that come into play here and no one to my knowledge has done any comprehensive serious scientific research into the subject taking account of all the variables and their combinations so we have to speculate around the little we know with the only proof being the success of the target and the absence of lead fouling, this indicates that that load combination is successful but not necessarily that our interpretation of why the load is successful is correct.

Then again what would I know as I am an old person who gets told by young people that I know nothing and that which I do know has no value in their modern world.

[FredB]

About 25 years ago, on a trip around the Eley factory, I asked this question. My reason was that my Walther GSP, shooting Eley Pistol, would accumulate a lot of bullet lube in the breach quite quickly and have to be de-gunged. Eley used a mixture of tallow and bees wax---I think they still do on the premium brands-- and it scraped off very easily. The answer I was given was a simple, pragmatic one: with the lube, in all test barrels, the ammo was more accurate.
Fred

[ColinR]

And I thought it was a simple question with a simpler answer. I am amased that something we take for granted and use without further thought can elicit such discussion. Obviously a far more complex subject than most of us could ever accept. As ever Adam puts forward some well considered theories, but even he accepts they are not proven. Probably best to carry on using lubed lead bullets and not thinking too much and just enjoy. They seem to work OK whatever.

[Rockhopper]

When you think about it the whole way a firearm works is not really cutting edge science. You ram a hard metal object down a slightly harder metal tube thats not quite big enough to accept it and you make it fit by burning a not insignificant quantity of propellant behind it. Its no wonder that all kinds of physics comes into play.

[Mike95]

Gas checks will help prevent fouling in addition to lube.....anything over 1300 fps will usually shoot better with a gas check. I also use the h and n high speed bullets which have some sort of plastic coating over about 6thou copper plating on almost pure lead.
I have used these to 2000+ fps with no sign of copper fouling...not sure about the plastic!!

Mike95

[dromia]

Gas checks them selves don't check gas, what they do do is stop the shearing of the bullet as it enters the rifling, being of harder material it grips the rifling and keeps the bullet centred in the rifling, think of it as a cog engaging the rifling. By stopping the bullet stripping and shearing it keeps the bullet fit intact so that the seal is good and there are no spaces for the gas to pass through and over the bullet. The base of lead bullets does melt it is only thin flash flakes and the thin edges of the bullet that are thin enough for the passing gas to have an effect on.

A good tough, not hard, alloy is what is needed for high velocity. With my high velocity alloy I have shot plain base bullets with accuracy and no fouling at over 2000 fps.

[dromia]

In relation to copper fouling the best way I know of stopping this nastiness is to shoot cast bullets.

[Maggot]

I thought it also helped to prevent oxidation as well, so you dont get orrible powdery lead oxide and pitted bullets after a while in storage....although I expect in theory ammo should not be stored that long.

[dromia]

I have decades old unlubed cast bullets in my reference collection that have no oxidisation and look as good as the day they were cast.

Sounds like you need to get your breath checked out if your bullets have that problem.