Types of leading and cause/fix

[Brad]

A while back Jim asked what leading was. I want to expand on that and ask more about the location of the leading, the cause, and how to prevent/fix it.

Most of us have had leading in the forcing cone. I know I certainly have.
I have had leading in the throats of revolver cylinders, but not any more.
I have most often had lead along the edge of the lands part way down the bore, usually towards the breech.
I have had leading in the throats of many fixed chamber firearms, both handgun and rifle.
I rarely get true leading at the muzzle but often get the grey antimony wash.

Anyone care to comment on a cause and cure for any of these?

I will as having some minor leading in the throats of my 1911. I figured my taper crimp was sizing the bullet down a bit and the slightly undersized front band was letting some gas leak by giving me the leading. I backed off the taper crimp. I shot 200 rounds today and that leading was gone. Instead I had leading along the lands. I'm pretty sure it is because my alloy was a bit too hard to maintain the seal on the trailing edge. The modified BR I used didn't seem to flow as well as I would like, I found a bit of it the grooves of some recovered bullets.

Next time out I use softer alloy and that leading should be gone. Counters what most expect but harder often makes leading worse, not better.

 

[USSR]

Yep, hard to counter the thinking that harder must be better. And, the commercial casters do us no favor by offering only 12 BHN or 18 BHN bullets, and their stupid "calculator" that supposedly tells you what BHN bullet you need for a certain pressure level (which just happens to tell you that you need their super hard bullets). A pox on your high antimony alloy, tin is your friend.

Don

 

[Ian]

Tin is not always your friend, it depends on what you're doing and many times can be your enemy.

I like my bullets about as soft as will still hold the rifling, mainly because they generally shoot better and lead less that way.

The good old 1911 .45 has taught me more about leading than just about anything else. In particular my Kimber 1911 that was my IDPA gun and happened to have a reverse-taper to the barrel. Soft bullets and Unique or 231 was the fix, keep 'em slugged up all the way to the crown and no leading. Except throat leading. That's when I found out about not shooting .453" bullets through it even though it will chamber them with room to spare. Thank ol' BD for his frequent retorts to those who always dispensed the wisdom of "size larger" to those having leading woes of any kind. The straight-wall semi-auto cartridges which (theoretically, not actually in most instances) headspace on the case mouth and thus have a sharp chamber terminus that's as close to groove dimension as possible are shave-o-matics if your bullets are too big, so BD would implore people to try sizing down to .451".....and by golly sometimes that fixes the problem.

So leading. Well, you get two kinds: The kind caused by gas abrasion (loss of obturation/seal of the bore by the bullet), and the kind caused by direct mechanical abrasion. The first kind is usually a gun problem (choke point somewhere), sometimes an alloy/powder mis-match, sometimes the bullet is just too small to start with for a number of reasons. The second kind is also caused by alloy/powder mis-match, alloy/velocity mis/match, or loose bits of lead scraped off either through seating/crimping or on the edge of the step at the end of the chamber. Sometimes bullets get bumped up in the case neck and rake off rings of lead in the throat which gets physically ironed-on the bore....that's where the lumpy, heavy deposits in the throat or first inch or so of the barrel happen. Streaked lead is usually loss of bore obturation causing gas-abraded particles to get blown by the bullet and smeared thinly into all the nooks and crannies of the rifling.

Notice I didn't mention lube quality or lack of it here. Leading due to lack or loss of lube does happen, but usually I can attribute that to only very high-pressure loads with a lube lacking any sort of "stop leak" quality, i.e. lacking something like a grease thickener which acts as a microscopic stop-leak under boundary lubrication conditions, so it falls under the gas-abrasion category even though a lube substitution can fix it.

Then there's this thing we call "antimony wash". Actually it's more like an alloy oxide wash, and it's a medium-grey coating on most of the bore surfaces which will mostly wipe out with a single dry patch...mostly. I don't know what causes it but I know when it shows up. When you start pushing the limits of an alloy's "feed rate", or how fast it can blast down the bore against the steel surface before the bullet surface begins to simply give up all over and start shedding itself, or whatever is happening. Usually my most accurate HV rifle loads happen in the sweet spot where I'm getting some antimony wash very consistently, it almost acts as a C.O.R.E conditioner.

That's all I got.

 

[gman]

Shooting way to hard commercial cast bullets long ago in my 1911 45 acp introduced me to extreme leading.

 

[USSR]

Tin is not always your friend, it depends on what you're doing and many times can be your enemy.

Sorry, Ian, but you and I are going to have to respectfully disagree. I have done handgun testing with an alloy that is high in tin and low in antimony (which is specifically not recommended on this site) , and the results have been outstanding.

Don

 

[Rick]

Sorry, Ian, but you and I are going to have to respectfully disagree. I have done handgun testing with an alloy that is high in tin and low in antimony (which is specifically not recommended on this site) , and the results have been outstanding. Don

Need to define "handgun testing". No doubt your results are accurate in low pressure low velocity cartridges but not all "handguns" fit this description. I'm a believer of Sn in most all of my casting but I keep the Sb/Sn percentages fairly well matched. Free tin (more Sn than Sn) in an alloy at high velocity will lead to "tinning" the bore. A good bullet fit In the firearm along with low pressure/velocity will cover up a lot of what could otherwise be a problem.
.

 

[USSR]

I cast hollowpoints almost exclusively. While there is a lot of leeway with regular cast handgun bullets as long as they are sized and lubed properly, if you want good expansion properties with a hollowpoint, then you've got to have a good alloy. This is especially so with low velocity rounds such as the .38 Special and .45 ACP. My Pb/Sn/Sb alloy of 96.5/3.0/0.5 creates perfect mushrooms as low as 800fps and as high as 950fps (that is as high as I have gone) in the previously mentioned cartridges. As soon as I get my new digital camera set up, I will show you the results.

Don

 

[Rick]

45 ACP 200 gr 2% Sb and 2% Sn fired into water at 900 fps. Water is a hard medium and won't give an idea of what happens in a game animal but does give an idea of how well the alloy holds together.
.

 

[KHornet]

Being old school, I expect SOME leading when shooting cast bullets. Sizing and lubing has
IMO much to do with leading in rifle and handgun. To small and the wrong sizing will almost
always produce leading. When that happens I go larger, and try different lubes.

Since Bencame up with BR and Bll however, I have had little to no leading (trace) in my rifles, and
very minimal leading in my revolvers. Pistols have been a bit more of a problem but that
often has proven to be bullet shape, usually correctable with a shape the pistol likes.
Just an old man's opinion.

Paul

 

[USSR]

Rick,

You can plainly see the effect of antimony on your expanded bullets: fracturing. Check these out at from left to right: 224gr MP 454-423 fired from a Colt Gold Cup at 800fps (SWAG), retained weight of 219gr; 165gr pentapoint MP 359-640 fired from a 2.5" S&W 19-3 at 840fps, retained weight of 163gr; and 161gr hollowpoint MP 359-640 fired from a 2.5" S&W 19-3 at 945fps, retained weight of 159gr. Simply no need for high amounts of antimony in sub-1,000fps handgun loads.

Don

 

[Brad]

My handgun bullets are generally range scrap. Mine rounds around 1.75% Sb and .5% Sn. It air cools to around 13-14 BHn but will heat treat closer to 18.
It works well for all but the stoutest of loads.

A high tin alloy will work well for lower velocity HP bullets. Probably the best thing for them. Where it starts to fall apart is when you really begin pushing them hard.

Match the alloy to the pressure and velocity expected. 20-1 isn't going to work well for 2500 fps loads in a Hornet but Linotype isn't best for 800 fps wadcutted in 38 special either.

 

[freebullet]

Well, to cause leading the quickest.

Overtighten your crimp. Makes sweet smoothbore from rifled barrels. Hey, maybe a good way to hide barrel pitting...?

Use to much antimony & don't harden the bullet. Gives a spectacular wash that seems to start from the muzzle end. Doesnt seem like hardened high antimony does it till ya get the velocity & pressure way up there. Also a light tumble lube can mask this issue.

In general I try to make loads that don't do those things.

 

[Rick]

Yes Don but as I said, fired into water. Not a lot different than shooting cement, very hard on a bullet and they stayed together pretty well. Will also have zero comparison to flesh. Same alloy I use in everything from these 45's through very top end magnum long range revolver and rifles to 2000+ fps. Why do I use this alloy in everything? Simply because of how well it works in everything combined with 800 pounds of it very carefully blended to be all the same.

I just now came back from shooting this same alloy in the 45 in SAECO 068 200 gr. Fired at about 25 feet into fine wet sand, amazingly NO bullet deformation, not even the nose. With the exception of rifling engraving couldn't tell they had been fired. The 068 also had amazing penetration in the sand.
.

 

[Ian]

USSR, the point I and Rick are trying to make is this: You make a GENERAL statement about tin, like it should apply to every single bullet ever cast by anyone, when the reality is that statement applies to only 5% -10% of what the audience here does with a cast bullet. This isn't a matter of disagreement, it's a matter of perspective which we have and you evidently do not have because from a previous thread I know you do not shoot cast bullets in rifles or at magnum-level in handguns. This is akin to arguing that the world is flat and mountains and oceans don't exist because you've lived in Kansas all your life.

Most people do not cast hollow points much if at all, and don't exclusively shoot low-pressure, low-velocity handgun cartridges. For the niche purpose of handgun hollow points at 800 fps, you are absolutely correct that lead and tin with as little antimony as possible is an excellent choice, though it STILL not the only good one. Try 1% tin 1% antimony and water drop it from the mould sometime, it will work as well if not better than 20:1 and save you a lot of money on tin.

Rick's point about an undersquare alloy and "tinning" is spot-on, I've made quite a mess of things attempting to use a low-antimony scrap with a lot of tin added to make 16:1 and 20:1 before, and found out one cannot ignore a small antimony content because it creates a nodular alloy that is sticky and fouls the bore like the dickens when pushed hard.

If you still disagree with me that high tin content is not always your friend (that doesn't mean "never", by the way), go pour yourself some binary lead/tin 30-30 bullets and send about 20 of them downrange at 2200 fps.

 

[Brad]

Why did I get the leading I described in the first post? Because I used an alloy that wasn't appropriate for the load. In my 44 mag with full loads that alloy would be great, for a 15,000 CUP load it was all wrong. The leading proves that.

I generally use straight range scrap for all casting but there are times where it pays to add some Sb or Sn. When to do that is part of the learning curve.

 

[USSR]

USSR, the point I and Rick are trying to make is this: You make a GENERAL statement about tin, like it should apply to every single bullet ever cast by anyone, when the reality is that statement applies to only 5% -10% of what the audience here does with a cast bullet.

Hmm, Ian, considering the following quote by you, I think it's a case of the pot calling the kettle black: "If more tin than antimony is present, the alloy will consist mostly of lead intermixed with Sb/Sn and a lot of free tin "nodules", which can be problematic and should be avoided, so keep your tin exactly at or less than the amount of antimony in the mix". I am rapidly getting the impression that you guys don't like anyone questioning you. Sorry if I am in the 5% - 10% minority here and my input has little value. And your "the world is flat and mountains and oceans don't exist" slam was a really low blow. I must say, instead of me trying your water drop alloy, why don't you get off your high horse and try my alloy? As you can see from my pics, it is a much better alloy than Rick's 2% Sb and 2% Sn alloy.

Don

 

[Rick]

As you can see from my pics, it is a much better alloy than Rick's 2% Sb and 2% Sn alloy.

Don

Better at what?

Since your so pleased with your alloy you most certainly should use it. It is however not the only alloy.

As to the pissin match . . . it stops now.
.

 

[USSR]

No pissin match, simply defending myself. Better at what? Look at how the excess antimony is causing fracturing. I shot mine into water too.

Don

 

[fiver]

if you really look at USSR's alloy.
break it down into what it truly is doing.
the percentages are too far apart.
it should IMO behave more like a 40-1 alloy but with a very small percentage SbSn chain within the alloy.

the free tin is far too much to lock on to the antimony and then try to break away at the last minute like a higher percentage antimony alloy would behave.

at his lower velocity's he will be mimicking the old factory 38 special and 45 colt recipe's.

 

[fiver]

oh jeez the actual thread.

there is another type of leading that some overlook and that is where other junk already in the barrel pulls alloy away from the bullet and holds it in place.