Welcome to the madness. This thread is to discuss and enlighten reloaders as to the goings on with lead bullets, how to load them, how to shoot them, how to eliminate and prevent leading, and how they are made. Lead bullets behave differently than jacketed or plated and there are certain conditions and limitations that need to be addressed when using lead bullets. I will attempt to answer the most common questions and issues concerning lead bullets.
It is not my intent to sound arrogant or condescending. If it comes across like that, I apologize in advance. I tell it like it is. I am far from an expert, but do have a bit of experience in the lead bullet world. Since most reloaders here are not bullet casters I won't discuss much of it here but save it for another thread on how to cast bullets.
My qualifications are I have been handloading since the fall of 2006 and in that time, according to my notes, I have loaded over 100,000 rounds. I have been casting my own lead alloy bullets for a little over a year and have been running my own bullet casting business since October 2007.
With that out of the way, lets begin.
Lead bullets aren't usually pure lead. Muzzle loading and black powder firearms use pure lead bullets, but we will be focusing on smokeless powder firearms. Common lead alloys for bullets include three elements: lead, tin, and antimony. Lead makes up the bulk of the alloy. Tin is used as a hardening agent and also helps to fill the mold completely. Antimony is a hardening agent more so than tin. Tin also helps to increase the quality of the alloy, but is expensive. Prices are anywhere from $5-8 per pound.
Very few places start with virgin metals and mix alloys from that. They usually use scrap metals and mix the metals together to get the desired alloy. This is common especially in today's commodity markets.
By varying the bullet alloys with the three common metals, the caster can achieve a specific bullet hardness. The hardness is rated on a scale called the Brinell Hardness Number (BHN). Pure lead has a BHN of 5. Wheel weights (WW) which is a common source of lead alloy for both home and commercial casters has a BHN between 9-12.5 depending on the manufacturer of the WW. Most I find have a BHN of 11-12.
There are some alloys commonly used in bullets. There hardness ratings in BHN are as follows:
WW (stick on) 6
1 to 40 tin lead 8
1 to 30 tin lead 9
1 to 20 tin lead 10
1 to 10 tin lead 11
WW (clip on)* 12
Lead Shot* 13
Lyman # 2 15
Water quenched WW 18
Linotype 18 - 19
Monotype 25 - 27
Oven heat treated WW 30 - 32
*Lead shot and WW have .25 to 1.0% arsenic (depending on the manufacturer) and can be used as a hardening agent when heat treating lead and lead-antimony alloys. 1/4 of 1% arsenic is all it takes. Adding any more than this adds nothing & will not further harden the alloy. Additional hardening can be achieved by heat treating when arsenic is present to approximately 30 to 32 BHN.
Casting is quite simple. The basics are you melt lead alloy in a melting pot and either use a ladle or a bottom pour melter to fill the mold cavity or cavities through a hole in a plate on the top of the mold called the sprue (sproo) plate. You fill the mold cavity until you get a good nickel to quarter size collection of molten lead on the top of the sprue plate. Then wait a few seconds for it to cool. Larger bullets, like 500gr for the 45/70 take up to a half a minute to cool. When the sprue, the lead left on top of the plate, is hard is it time to cut the sprue and drop the bullets.
Take a wooden or rubber mallet and whack the sprue plate open with enough force to cleanly cut the sprue from the bullet base. It doesn't take much, don't He-Man it. Just a good stiff tap and then swing the plate clear of the bullets. Now invert the mold and open it up. If they stick in there, tap the center screw of the handle to release them. NEVER EVER UNDER ANY CIRCUMSTANCES HIT THE MOLD BLOCKS. This will damage them as they will become misaligned and make bad bullets.
When they drop, close the mold up, swing the sprue plate back over, and go do it all again.
Now we are going to address the issue of leading. Grab a cold one. This might take a while.
To determine the correct size bullet for your firearm, you need to slug your bore. Slugging a bore means to push a soft pure lead slug (bullet, sinker, mass) down the barrel. I use a cleaning rod and a mallet. Some use wooden dowels. Same results. When slugging a bore, you will have a negative impression of the bore dimensions.
The largest dimension of the slug is the groove diameter of the bore. This is the measurement of interest. The smallest portion of the slug is the land diameter. We don't use this in the cast bullet world. Your bullet diameter should match or be +.001" over the groove diameter for pistols and rifles. For revolvers, they should match the smallest throat of the cylinder. See below.
In pistols and rifles, it is easiest to slug from muzzle to chamber as you can work the slug back into the action in a straight line. For pistol barrels, I remove them and put them in a vise.
Same deal with revolvers-muzzle to breech, but I swing the cylinder out and put the whole gun in a vise. For slugging the throats in a revolver cylinder, you do the opposite, work from back to front (barrel points away from you). Each throat dimension might be different than the others. It is recommended to get the throats matched (reamed to same size) to optimize for lead bullets.
In revolvers, you are working with two pieces, the barrel and the cylinder. Ideally the throats should measure .001" over groove diameter. So for the 38/357 Mag, groove is usually .357-.3575" and groove should be .358-.3585". In Ruger GP100 revolvers, the groove is .3575" and the throats are .357". This gun is optimized for jacketed bullets. A simple throat ream to .358" is needed to optimize. Some revolver throats are grossly over sized, as is the case with many .45 Colt guns.
Leading is a relationship between these elements: chamber pressure, bullet hardness, and bullet fit, assuming your lube is up to the task of withstanding all these factors.
We already addressed bullet fit above, your bullet diameter must match groove diameter or in revolvers, the throat diameter.
Bullet hardness and chamber pressure are related. Obturation is when the bullet expands under pressure to fit the groove of the barrel. For a given chamber pressure, if the bullet is too hard the bullet won't obturate and gas will leak around the bullet into the grooves and you will have leading. Or it could be said that the chamber pressure is too low for the hardness. Sort of a partly cloudy/partly sunny thing.
To find if your bullet hardness is up to the task of bullet obturation under your chamber pressure, multiply the BHN rating by 1422 and that will get you the pressure needed to get complete obturation. Or if you know the chamber pressure of your handloads (via data in the manual) divide that number by 1422 and that will give a BHN rating to get complete obturation.
For the most part, handguns do well with BHN ratings between 9-12. Magnum velocities will dictate a BHN of 15, the old Lyman #2 alloy.
Truth is most cast bullet manufacturers don't make hard (+15 BHN) bullets because they are any better than softer bullets. They do it for damage control. Most casters ship bullets to customers and they make their bullets hard enough to withstand the rigors of being handled by our beloved USPS workers.
I run cast bullets in my guns ranging from the 32 H&R to 45 Auto to the 10mm to 45/70 to 375 H&H Magnum. Ninety-five percent of my bullets are cast at a BHN rating of 14 and I get no leading at all.
Causes of leading are related to the above information. Chamber or forcing cone leading is mainly caused by shooting a bullet that is too hard or too small. Check bullet fit to groove diameter or cylinder throats. Adjust BHN to suit chamber pressure.
Breech leading is usually caused by too soft of an alloy. Leading here is just forward of the chamber. Adjust BHN to be harder. Should take care of it.
If you get leading near the muzzle, quite simply your lube sucks or isn't enough to do the job. Your lube is running out before the bullet gets to the muzzle. Not good. If you can switch to a design that carries more lube, it should do the trick. If you get a lube "star" at the muzzle crown you bullet has plenty of lube and is working well. If you have a lead "star" at the muzzle crown, you are running out of lube. You might be able to reduce the velocity and be OK. Try that first. The quicker you push a bullet, the faster it runs out of lube.
If you get leading along the entire bore, most likely your bullet is undersized. Review the sizing steps and bore slugging to determine your needs and make adjustments. Sometimes increasing bullet diameter .001" makes all the difference. Don't worry about bullets being up to .003" over groove diameter, as long as they chamber safely.
The burning gun powder will not melt the lead. That is a myth. Lead alloys melt at 600-700°F and the fraction of a second the bullet base is exposed to the burning gun powder is not even close to being hot enough to melt it. If you want proof, examine wads used in shotguns or black powder cartridge loads after firing. They may show slight darkening, but won't be consumed in flames either! If the burning powder won't melt the plastic or burn up the cardboard, why would it melt a bullet base? The answer is, it can't.
Commonly, lead bullets can't be shot as fast as jacketed bullets can. This is especially true with rifles. Yes you can shoot lead bullets in rifles and I'm not just talking 30-30 and 45/70. You can shoot lead from the 17 Remington to the 458 Winchester Magnum. When you enter the world of shooting lead in your rifle you need to forget the world of 3000fps jacketed and focus on the 2000fps world of lead.
The lube qualities are really what is holding us back. We haven't come up with a lube that can hold up to a velocity of more than 2700fps. At that velocity there are more things being done than I can address here. I'll just say it takes a dedicated lead shooter to develop a load that fast that doesn't smoke much or lead the bore.
Loading lead isn't much different. You might need a bit more bell on the case mouth so you don't shave the bullet when you seat it. You will have to clean your dies more often as lead and lube residue collect in your dies more readily. I clean mine every 1000 rounds or so.
My fingers hurt right now so I will continue this tomorrow.