how does lube prevent leading?

I guess it does in two ways:
1 - the lube contacts before to the barrel than the melting lead part of the bullet (the bottommost part of it)
2 - the lube of the previous bullet remains there (or part of it) ready for the following bullet.

Franky50 said:

melting lead part of the bullet

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The brief amount of time lead bullet surface is exposed to burning powder gas is not long enough to melt it.

Rather, bullet base experiences gas blow-by and gas cutting from high pressure gas and this "bullet base erosion" many reloaders confuse as "lead melting".

Boolit fit to bore is king!

I think this is the reloaders "Question of the Year". When I started casting I researched everything I could get my hands on concerning all aspects of ( a few books and "From Ingot to Target") and I found that nobody knew for sure how lube works. I saw some believe it did in fact lube the bore, some said it sealed the bullet/bore and some even admitted that they didn't know. Some said bullets don't melt from the high pressure and high heat and some produced fired bullets with melted and distorted bases. So, I'll bow to the experts and just say my bullets lead my barrels and fly everywhere when I don't lube them...

All you'll ever need to know and more.

(link is to Glen Fryxell's Casting book)

I have a Trapdoor that leads something awful. I have been using commercial cast bullets and for whatever reason, the commercial lube is not preventing leading.

This was an experiment that worked. I dipped these rounds, heavily dipped these rounds, in Lubriplate A130. The cartridges were loaded with AA5744, a smokeless powder. This god awful amount of grease positively stopped lead fouling in the barrel. Grease was squeezed out the action, the first shot shown with a clean action, and I think the greasy action was after a number of rounds. Grease is squeezed back around the cartridges and out the action, and, out the bore. I clearly saw grease plumes in front of the barrel when I fired.









I did not notice any abnormal velocities with my load.

M1873 Springfield Trapdoor 1884 rebuild

405 LRN 27.5gr AA5744 R-P cases WLR trimmed 2.085"
Heavily greased with Lubriplate 130A

14 Aug 2014 T = 78 °F

Ave Vel = 1346
Std Dev = 15
ES = 38
High = 1371
Low = 1333
N = 5

I also looked down the barrel to see what was going on. I am of the opinion that I saw evidence of lubricant coating the bore, from throat to muzzle. Grease prevents leading by creating a lubricant barrier between the lead bullet (or jacketed bullet) and the bore. Grease is a mixture of oil and an thickener, and it is well known that the oil in the grease provides the lubrication. So, oil must be in the bore and preventing contact between the bullet and the steel.

I have shot thousands of lubricated 45 ACP target loads, where I oil the cases just at the junction of bullet and case, or sometimes the entire bullet, from shoulder to base, I clearly see evidence of an oil coating in the barrel. My M1911 target pistol cleans very quickly at the end of a match. I do not have lead fouling or any sort of leading when I oil my ammunition. So, oil must be in the bore and it is positively preventing contact between the bullet and the steel.

I saw absolutely no evidence of irregular velocities due to oiled ammunition.

M1911 Les Baer Wadcutter

200 LSWC (H&G 68 type) 3.8 grs Bullseye Lot 919 11/2005 WLP Nickle, mixed cases
8-Jun-15 T = 91 °F OAL 1.250" Taper Crimp 0.469"
oiled cases

Ave Vel = 714.4
Std Dev = 17.17
ES = 77.2
High = 755.1
Low = 677.9
N = 30

accurate

200 LSWC (H&G 68 type) 4.0 grs Bullseye Lot 907 6/20/2005 WLP Brass mixed cases
23-Mar-16 T = 69 °F OAL 1.250" Taper Crimp 0.469"
oiled cases

Ave Vel = 723.3
Std Dev = 9.48
ES = 28.65
High = 741.6
Low = 712.9
N = 10

200 LSWC (H&G 68 type) 4.0 grs Bullseye Lot 919 11/2005 WLP Nickle, mixed cases
8-Jun-15 T = 91 °F OAL 1.250" Taper Crimp 0.469"

oiled cases

Ave Vel = 742.9
std Dev = 9.89
ES = 33.19
High = 760.6
Low = 727.5
N = 20

accurate


200 Xtreme Plated SWC 3.7 grs Bullseye Lot 907 6-20-2005 WLP Brass mixed cases
23-Mar-16 T = 72 °F OAL 1.250" Taper Crimp 0.469"

oiled cases

Ave Vel = 651.7
Std Dev = 11.66
ES = 40.03
High = 676.9
Low = 636.9
N = 14

all ejected, slide failed to lock back once


200 Xtreme Plated SWC 4.0 grs Bullseye Lot 907 6-20-2005 WLP Brass mixed cases
23-Mar-16 T = 72 °F OAL 1.250" Taper Crimp 0.469"

oiled cases

Ave Vel = 686.8
Std Dev = 26.32
ES = 91.37
High = 730.4
Low = 639.1
N = 14
accurate, functioned and slide locked back

When I started casting I worried about how the lube works to prevent leading and tried a few options which were hit or miss. Now I powder coat with no problem. Same easy procedure for every bullet (besides adding gas checks where desired) and no lead to barrel contact.

My initial post of lube working to prevent leading got deleted during the thread merge.

I am out of town at the moment and will attempt to repost when I return home tonight.

With no offence intended to anyone, I think it's all "like some folks think"...

Well as most have mentioned lube does play a very important part of the equation when shooting cast bullets.

Also mentioned was that fit is King, but they left out the part about lube being queen. You have to have the proper size bullets or slightly bigger than needed to ensure the fit tight as they pass from the case, through the chamber or cylinder mouth, and down the grooves of the barrel.

Another couple of things that can cause leading are bullets being used with the alloy either too hard or too soft for the application. Either one can and will throw down a goodly amount of cast off in your barrel, having good lube or not.

Working with cast bullets in modern firearms is simply a balancing act. You have to first have the proper alloy for the pressure you plan to load too. Then you have to use a lube that is substantial enough to hold up and make the trip down the barrel before giving up or migrating out. Sometimes you get it right and sometimes it takes making a change in burn rate or a bit softer or harder alloy.

If a lube is working properly and the bullet fit is good, then what is supposed to be happening is the lube is coating the barrel as it pumps out of the lube grooves and prevents the alloy from the succeeding shots from tinning to the barrel, as per an Ideal handbook from early in the 1900's.
Gas checks don't scrape anything, what they are supposed to do is protect the base and sides of the bullet from being gas cut and depositing lead in the barrel.
Biggest culprit in leading is from poor bullet fit, the bullet being to small for the throat in a rifle will allow for blowby when the round goes off and gas cutting the base and sides of the bullet. Leading begets leading and once it gets started in the barrel it just continues to grow and spread..

The same way oil in the engine prevents the connecting rod bearings from becoming peanut butter.

By reducing friction?

By providing a molecular film preventing metal to metal contact.

Walkalong said:

How could I be offended when I don't know what that means.

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It means everybody has their idea of what happens in a gun's barrel when a cast bullet is fired and most is plain old opinion. From my research I've not been able to find any reports of seeing or proving exactly what happens in the barrel. I have read of some "conclusions" that come from testing, but still not 100%proven facts...

We certainly do know that leading isn’t due to mechanical friction between the bore and bullet. You simply can’t get lead to rub off onto a piece of steel by mechanical friction unless the steel is shaped like a file.

Possibly grouchy. But it isn't pleasant to have one's spelling, terminology or vocabulary challenged. Especially on line when only black letters on a white background are used to convey an idea...