Economy minded shooters have a love-hate relationship with cast bullets. We love the economy, many of us hate the cleanup. I can sympathize, cleaning a badly leaded barrel is one of the biggest pains in the butt since the invention of the hemorrhoid. Many shooters, even handloaders, avoid the lowly lead alloy bullet for this very reason. It doesn't have to be that way.
There is a lot of good information about shooting the lead alloy bullet that has almost passed from general knowledge as our grandparents passed from the scene. The first bit of information that has been lost is that cast bullets don't have to lead a barrel, and won't if they're the right size, hardness and properly lubricated. This, of course, assumes that the barrel in question isn't full of rust, pits and tool marks. The first step in our quest to eliminate barrel leading is to remove all traces of jacket fouling from our tubes. Fortunately this is easy. A strong solvent like Sweet's 7.62 will remove every trace. Simply run a very wet patch or two through the barrel, wait ten minutes and then dry patch. Warning! Do Not forget about it and leave the strong solvents in the barrel. There have been incidents of these solvents "etching" the barrel when left in. I always like to run a couple of patches of Hoppes Number Nine through the tube after dry patching. I leave that in for a while just in case of burnt on powder residue. Then I repeat the Sweet's, dry patch and Hoppes until my dry patches show no trace whatever of that blue-green jacket fouling. Don't scrub and scrub with a brush, let the solvent do the work.
I am seldom in a hurry so I don't often use the Sweet's. I use Butch's Bore Shine instead. It's a less aggressive solvent that is safe to leave in that expensive barrel. Run a couple of wet patches through and then leave it for a few hours or even overnight. Then dry patch and repeat until we again get no trace of that blue-green. Follow up with a regular gun oil.
Getting the jacket fouling out will eliminate at least half of the potential leading before we even look at the lead bullets.
Next we look at the size of the bullet. Obviously I'm not discussing .45 caliber bullets in a .22. It's important that the bullet be just a thousandth of an inch or two larger than the bore, this keeps the powder gases behind the bullet, where they belong. We have a little leeway here. If the bullet is as much as three or four thou over it seems to swage down just fine. For that matter, unless our alloy is too hard, the kick in the butt from those high pressure gases will slug it up to fit. The proper term for this is obturation, The trouble is, most of the storebought cast bullets are too hard to do this with mild loads. A mistake many handloaders make when shooting storebought cast bullets is going to a lighter load when they get leading. It's counterintuitive but the answer to leading is often to increase the pressure.
There is a simple working mathematical formula that can tell the minimum pressure needed for proper bullet obturation. It requires that we either have a Saeco lead hardness tester or at least know the number that this device gives to the more common lead alloys. The most common commercially cast bullets run a fairly hard alloy, usually the old 85% lead. 5% tin and 10% antimony, this gives an LHT number of around nine or ten. The formula is LHT multiplied by 2,000 + the required pressure, we need a load that gives in the neighborhood of 18 or 20,000 PSI to allow a too-small bullet to slug up. This is important because this is over the allowable pressure for a lot of cartridges and guns. For instance my Cimarron clone of the Colt Single Action Army only allows a maximum average pressure of 14,000 PSI. This means that storebought cast bullets must not be too small because they aren't going to slug up. This is compounded by the fact that the revolver's chamber throats are supposed to be bigger than the bore. In order that the powder gases stay behind the bullet, then, my bullet must be large enough to plug up that chamber. I have two different brands of store-bought cast .45 bullets on hand, Meister and Rucker, both are plenty tight in the barrel, both are too small for the chamber throats. Both are too hard to slug up in those throats meaning I get gas blow by until they're in the barrel proper. There is a very simple way to tell if that bullet is too small for the chamber throat. If we can push it through the cylinder's chamber by finger pressure, it's too small.
Gas blow by is a Bad Thing. It robs the load of power and that hot, high-pressure gas blows the lube out of the groove meaning I've got bare, unlubricated lead going down my barrel. This is why I cast my own bullets. I can size them to fit my particular gun and I can use a soft enough alloy to slug the bullets up at low pressures.
Oddly the suppliers of cast bullets to the handloading trade know that their bullets are cast of an alloy that is too hard for best results in all but full power magnum hunting loads. They know that these magnum hunting loads are less than a quarter of what we actually load. The trouble is that the soft bullets get beat up in shipping and handling. There are a very few commercial casters making soft bullets for the low pressures involved in Cowboy Action Shooting, these bullets are quite a bit more expensive than the hard cast because they have to be carefully packed to avoid damage in shipment. One such supplier is Desperado Cowboy Bullets, LLC.
There are three answers for the handloader that wants those pleasant-shooting low recoil lead bullet loads. Cast your own or buy the more-expensive Cowboy Action bullets. Another answer is the swaged bullets from Hornaday, Speer and Remington. They're available in the most popular calibers, Midway, among others, stocks them. Those swaged bullets are usually a bit more expensive than the cheapest cast bullets, they're quite a bit cheaper than buying those soft-cast.
The third answer is a simple one. Let the barrel lead. Just shoot the cheap bullets and don't worry that the inside of your barrel is looking like a poorly-maintained sewer pipe. It takes quite a bit of leading before accuracy starts to degrade, odds are that you'll be ready to stop shooting before it does, Then, at the end of the shooting session shoot half a box or so of jacketed bullets. The lead will tin itself to those bullet jackets and leave the barrel. How many jacketed bullets it takes to remove all the lead depends on how bad the leading is. Bear in mind that there is no solvent that dissolves lead, not that won't dissolve the barrel. There are many solvents that dissolve jacket fouling. Forget scrubbing the barrel for hours to remove lead, shoot it out.
The shooter with an autoloader seldom has to worry that his store bought cast bullet will be too hard. The shallow rifling in an autoloader's barrel requires a very hard bullet. With only one chamber throat, instead of five or six there is less of a chance that the chamber throat won't match the barrel and, lastly, if the load is stout enough to work the action, chances are it's going to be stout enough to slug up the hard bullets. Working pressures in autoloaders run higher, anyway. While the revolver shooter has to worry that his bullet is too hard, the autoloader must worry that the bullet might be too soft to take the rifling. A too soft bullet in an original Colt .45 ACP will 'strip the rifling', meaning that it won't spin, it will just charge right through and not spin at all. Needless to say the inside of the barrel will be a real mess and accuracy will be nonexistent. It's my understanding that Glock specifically disallows using cast bullets in their handguns and that there have been KABOOMS resulting from such use. The going theory of why this happens is that the working of the cartridge from magazine to chamber scrapes off a tiny bit of lead from the bullet. As this lead builds up in the front of the chamber it eventually results in the gun firing with enough of the back end of the cartridge sticking out that it is unsupported, the cartridge case fails to hold the pressure and we get the KABOOM. I've seen one such gun and the cartridge case, the theory matches the look of both. There was no information on the number of lead bullet rounds were fired before the KABOOM. Avoid lead with Glocks.
Another autoloader that doesn't seem to work with lead alloy bullets is the Heckler and Koch. Here the problem is not KABOOMS but the lack of conventional rifling in the barrel. Instead of regular rifling the barrel is actually a polygon shape and cast bullets don't seem to work well. It's not a matter of safety but accuracy. I know of no serious experimentation with alloys and lubes to try to make cast bullets work in them. I suspect that those who are well-heeled enough to afford an H&K can afford jacketed bullets.
With those exceptions, the humble lead bullet is the way to go. In mild loads it's cheap and easy on recoil and muzzle blast. At the other end of the spectrum a well shaped lead alloy bullet will penetrate more deeply in large game than any expanding bullet. For the most horsepower from your magnum revolver it's a heavy flat-point hard cast bullet loaded to the highest velocity.
Update. I realized that I got ahead of myself and neglected to put the LHT number of some of the other more common bullet allys. Here are a few... One part tin to twenty parts lead is just under six. This is my preferred alloy for those low pressure smokeless powder loads. They'll slug up nicely at just under 12,000 PSI. That's perfect for standard pressure .45 Colt loads and other target loads where recoil and very loud muzzle blast are problems.
Another common ally is one part tin to thirty parts lead...giving a LHT of 2. This is a good alloy for black powder shooters, there is enough tin to help the alloy fill out the bullet in the mold, the main reason we add tin to our bullet metal, yet not so much that the bullet doesn't slug up for proper obturation at those low black powder pressures.
Common wheelweight metal runs about seven or eight on the LHT scale.
One of the harder alloys is linotype with an LHT of ten.
Heat treating common wheelweight runs the LHT number up to 12 or 13. This is hard enough for autoloaders and magnum revolver loads. Heat treating bullets is easy. Get a old cookie sheet, load it up with unlubricated bullets, put them in a 450 degree oven and leave them for about an hour, two hours if there's a large quantity of bullets. Let them cool in the oven and then set them aside for about 24 hours before sizing and lubing. Heat treating bullets made of linotype alloy makes them hard enough to use in rifle loads up to well over 2,000 feet per second if we use a good lube.
Update #2...I know half my links don't work, I can't figure out why. Just google them, I'm tired of fighting with them. Shucks and other colorful comments.