What's more likely to lead the barrel - soft lead or hard lead ?

[David R]

shot these today.

Gun DW PM-9
Range 50 yards
Bullet Missouri 125 Semi Wad Cutter Hi Tek Coated
3.5, 3.7 and 4.0 Bullseye. OAL 1.1" I have a long lead.



Sa you can see, the more the powder, the more the group opened up.
The 3.5 Bullseye is going about 1,015 fps.

Here a couple with 147 flat point Missouri Hi Tek coated.
3.4 grains Unique, AV 900 fps.
Still 50 yards.




There was no leading involved.

David

[Unclenick]

MG,

Melting has no bearing on leading. If you do a thermal analysis you find hot gases at 5000°F can't feed heat to the surface of any bullet metal fast enough to raise its temperature enough to start melting it before barrel time is over. Instead, because the metal conducts heat much better than powder combustion gas mix at that temperature (about 200 times better), it drops the temperature of the gas at the surface interface with it. Barrel time is done before enough heat can transfer to its surface to raise the temperature much. It's the same phenomenon as quickly passing your fingers through a candle flame without them feeling burned. Friction with the bore contributes more heat to the bullet than the hot gas does. The lead that sticks to the bore comes either directly from that friction or from bypassing gas mechanically cutting the lead and splattering it against the bore.

That formula in the MB article comes from the late Richard Lee's book, Modern Reloading (2nd Edition). It indicates bullets have to be harder than we usually buy them for minimum distortion by pressure. However, there are situations where having some distortion by pressure leads to less leading. The revolver barrel with a constriction in it at the frame is the most common example. When the lead passes through the constriction it is narrowed. But if it is soft enough, the force on the base that is accelerating it will cause it to slump back outward against the larger bore diameter after passing through the constriction. As long as the middle has done that by the time the base is clearing the constriction, it will keep the bore obturated, thereby preventing the gas escape that cuts the lead and splatters it against the bore. In that situation, if the constriction is bad enough, a harder bullet just gets sized down and may not spring out enough to obturate the bore and therefore will suffer from gas cutting.

Velocity limits on bullets are mostly if-y. You could argue that spinning one too fast will make it wobble or fly apart. That can happen, but that same velocity might be fine with a lower rifling pitch. You can argue you can't push a bullet past a certain velocity without distorting it too much. That can be true when the barrel is short and untrue when it is long. How much pressure you apply to the bullet and how much muzzle blast follows after it both have the potential to cause damage. Usually, it's a case-by-case experiment to see how fast you can drive one.

[Road_Clam]

Unclenick, If leading is not caused by melting than what is the function of added "gas checks" (or "wads") on bullets that will see 1400+ fps. Not to contradict your valued expert inputs, but i've read very credible input that leading IS in fact caused by melting especially within BPCR discipline of shooting.

[David R]

I don’t think you can melt the lead either. The gas check is a copper cup. It makes a perfect seal to keep gasses from getting by AND scrapes the bore clean.

They also make for a nice square base of the bullet on exit of the muzzle.

There are people who cut circles out of beer cans to make flat gas checks and claim they work too.

Just look st the base was f recovered lead bullets. The sprue is clear and defined.

David


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[David R]

Do a search for “ The Load “. By Ed Harris. 13 grains Red Dot in a 30-06 rifle with cast bullet. Those bases don’t melt either. No gas check, 1300 to 1600 FPS with a PROPER fitting bullet and decent lube.


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[Unclenick]

Originally Posted by Road Clam

Unclenick, If leading is not caused by melting than what is the function of added "gas checks"...

Exactly as the name implies, they check (stop) gas trying to impinge on the bullet base or trying to do an end-run around it, blowing lead off of it. Outside the bore, while the bullet is still subject to muzzle blast on its base, they stop the rapidly accelerating gases from beating up and taking lead off the bullet base.

When I was still active in bull's-eye pistol match shooting I made a steel front sight extension for my old Mk I Ruger bull-barrel target pistol. I was amazed by the size of the lump of lead that developed on the underside of the extension where it overhangs the muzzle. A lot of muzzle blast cut lead splatter caked up.

I don't know what to tell you about the advocates of lead melting as a mechanism. I can point out that smoothing bores, including in muzzleloaders, reduces leading substantially, which would not occur if melting was the mechanism by which it was deposited as the smoothing doesn't change the barrel time enough to make that kind of difference.

[HiBC]

With a centerfire rifle,if a primer has gas leakage around it,it will gas cut the bolt face pretty quick. The bolt does not even get warm. Gas cutting is a little diferent than melting.(OK,we can get into semantics,.I don't fee like arguing.Yes,the gas may melt the surface molecules)

Three gun shooters,etc who use comps on race guns,soon learn that open base fmj bullets will lead foul the comp

Bullets that cover the base solve the problem


I'll agree that bore surface finish is an issue . We refer to "pencil lead" for a reason. You can write lead on a piece of paper.

[gwpercle]

Undersized hard bullets lead way more than properly fitting soft bullets.....Every Time .

Fit is much more critical than hardness.

In the same load the undersized hard bullet doesn't slug up to fill the bore so you get leading the entire way . The soft bullet might slug up , fill the bore and not lead quite as badly .
Gary

[Metal god]

Melting has no bearing on leading.

At all ? what about hot burning powders heating up the bore . Will a hotter then average bore cause that friction heat to be higher ?

[David R]

If the bullet is lubed properly and fits properly it does not matter.

David

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[Unclenick]

Originally Posted by Metal god

At all ? what about hot burning powders heating up the bore . Will a hotter then average bore cause that friction heat to be higher ?

Barrel heat certainly affects pressure and velocity, probably mostly by the hot chamber transferring heat to the primer, changing its ignition characteristics. Heat affects the coefficient of friction, but not always all that predictably. Look at the table for COF of aluminum foil in this article and you will see it goes up and down again as temperature rises. A unilateral increase can occur with polymers, though, so powder-coated bullets may experience a change.

If you fire lead bullets that jam the throat in a full-auto weapon, you can probably fire fast enough to get the barrel really hot, and if you then leave a cartridge sitting jammed in the throat a few seconds, see some signs of melting. But I load lead bullets seated against the throat of my 1911's all the time and can say that after clearing a live round that has sat in the chamber several seconds after a rapid-fire string, it shows no sign of melting at the rifling contact marks. So spending a millisecond in contact with the bore, as when firing, certainly isn't going to melt it, either.

[res45]

There are many issues that can cause leading, bullet, lube or even the firearm itself can case a leading issues even when you have all your other ducks in a row. Here is a good read on Leading http://www.lasc.us/Fryxell_Book_Chapter_7_Leading.htm

Needless to say if the leading problem is not firearm related it should be an easy fix if you have control over all the aspects that go into making up your load in handguns or rifles.

Bullet fit is king followed by proper lube, then you load pressure / velocity requirements can determine what your alloy composition needs to be and if you need a plain base or gas check bullet. I shoot lots of both in handguns and rifles in all action types and leading is not an issue regardless of how many rds of lead ammo I put down the bore in one setting. Once you understand the causes of leading it doesn't have to be an issue.

[Metal god]

What about shooting revolvers . Aren't there designs them selves inherent to gas cutting The bullet needs to travel pretty far with what has to be gasses jetting all around the bullet before it engages the lands . Or is it the pressure is not high enough at that time to be cutting anything ?

UPDATE
Also went and shot those 50rds of Speer 158gr swaged LSWC with 4gr W231 out of a 6" GP 100 . There was no leading or very close to no leading at all . Bore still had very much a mirror shine to it with maybe a very light streak or two . Either way cleaner then any of the hard cast I shoot . There was stuff loose in the barrel after , which I assumed was unburned powder because just about all of it could be blown out with one breath .

It's a real light load in that big heavy gun and I'm not a fan of that light a load . That said I'll load up the rest of that box and likely buy more at some point just not a big fan of uber light loads .

[Doyle]

Metal god, 4gr of W231 with a 158gr LSWC seems really low. I see the Cowboy Action Shooters using 4.2gr (and everybody knows how low they like to go). I wonder if you'd like it better if you went up to just 4.5gr.

[USSR]

4gr of W231 with a 158gr LSWC seems really low

Not really. Assuming you are using .38 Special brass, Winchester lists 4.1gr of W231 at 16,000 psi and 900 fps out of a 6" barrel. Even if using the slightly longer .357 Magnum brass, you should still have a 800+ fps load. Don't like "uber light loads"? You will be surprised just how fast you can drive relatively soft bullets.

Don