Chapter 6.6.3 - Shooting Lead Bullets In Handguns, Cast Bullets For Beginner And Expert
Many are under the impression that hard bullets work best. Very often, the exact opposite is true. In many cases, use of softer bullets would be to one's advantage. The reason is that the softer alloys are more easily bumped up to fill the throat (obturate) when the powder is ignited. While depending upon bump-up of soft bullets cannot ever be as dependable as correct bullet fitting, it can help in some small number of instances.
Forcing cone leading is nearly always the result of oversize cylinder throats or undersize bullets, not because the alloy is too soft. In fact, sometimes, for a given powder charge, a softer bullet will shoot more accurately because softer alloys will allow for more complete obturation (bumping up) and reduce or eliminate gas cutting.
Correct bullet hardness for revolver target loads is about 8-12 BHN, depending upon the charge giving best bullet stability and the chamber pressure generated. The usable maximum chamber pressure of an alloy is a function of its Brinnell Hardness Number. As a rule of thumb, optimum chamber pressure for adequate obturation is about four times yield strength.
Within the range of alloy hardness used for typical as-cast or heat treated bullets (from 5-30 BHN), yield strength is approximated by the BHN multiplied by 480. This means that a soft alloy of 8 BHN, such as factory swaged lead bullets will stand up to about 15,000 CUP (8 x 480 x 4=15,360), and an alloy of 12 BHN will stand up to about 23,000 CUP. This corresponds to the pressures generated by 4-6 grains of fast burning pistol powders such as Bullseye, 231, Red Dot, Green Dot or 452AA, which are all well suited for the .44 Special.
The chambers of firearms have a nomenclature that needs be to be understood. Starting with the base, we have the main body of the chamber. Ahead of the body is the neck. In a straight walled case the neck is merely a continuation of the main body and is indistinguishable from it. The bottleneck case has a neck that is reduced in diameter to hold the bullet in a firm grip. Since this is a handgun chapter, we will deal mostly with the straight case but the fitting principle is the same for both case types.
Immediately ahead of the case neck is the chamber throat. This throat has also been called the ball seat or bullet seat. The throat is either straight or has a very slight taper leading to the forcing cone. The forcing cone is tapered from the end of the throat to the rifling origin. It is the diameter of the throat that is all important in choosing the proper bullet diameter.
When the round is chambered and fired, hot, high pressure gases begin to push the bullet out of the case and into the throat. It is here that, if a good gas seal is not realized, the bullet integrity can be compromised. As the hot gases impact on the bullet base they also tend, depending upon bullet diameter, to rush alongside the bullet between it and the throat wall, scouring the bullet. This action is properly referred to as gas cutting. The gas cutting blows a small amount of molten lead and lead vapor ahead of the bullet where some condenses on and attaches to the bore wall. The bullet then runs over the deposited lead, further degrading the bullet. In severe instances, enough lead can be deposited within five rounds to completely ruin accuracy.
Leading that is caused by gas cutting is easily diagnosed by examining the forcing cone of the firearm. If leading is apparent there, it is from gas cutting. If the leading occurs down the barrel or near the muzzle, it is a bullet lube problem; either not enough lube or one that is not up to the challenges of high velocity shooting. Lube failures are rare in handgun loads because of the relatively low velocities.
Gas cutting is eliminated, or at least significantly reduced, by making sure that the bullet diameter is no more than .0.0005" less than throat diameter. If the bullet is larger than throat diameter, as long as the resulting cartridge is not too large in diameter to chamber easily, it will work just as well regardless of the glossy gun writers claims about leading and excessive pressures. I have for many years commonly used bullets that are up to 0.007" over nominal bullet diameter in handguns where throats are grossly oversize. Unfortunately oversize throats are not an uncommon condition of either old or new firearms.
Remember, however, that it is not a safe practice to use oversize bullets that result in a cartridge that does not chamber easily because the neck must be allowed to expand slightly for safe bullet release. To attempt to use a cartridge so loaded is to risk generating excessive pressures
Cast Bullets in Revolvers
by Adrian Pitfield
It is assumed that the revolver concerned is capable of decent groups with either jacketed or plated bullets to demonstrate that it is a “good-shooter” so to speak. Before starting any load development with cast bullets, check the bore diameters of the cylinder and compare this with the forcing cone diameter of the barrel. Decent accuracy can be expected with the cast bullets as long as the cylinder bores are equal or larger in diameter than the forcing cone. If the forcing cone diameter is larger than the cylinder bores accuracy will be disappointing, but it is nothing a competent gunsmith could not put right. I like to check the correct bullet diameter by driving soft, oversized bullets or round-balls through the cylinder and checking the diameter. Then confirm this by choosing a bullet with this measured diameter and then drive these bullets through the cylinder using a wooden dowel. They shouldn’t fall through freely, but should need a moderate steady force to drive them through. Make sure the cylinders are really clean before doing this test otherwise there is a good chance of misreading the results. I then like to check the maximum cartridge length with this bullet/gun combo. Make up a dummy round – it goes without saying of course no powder or primer Having chambered the dummy then measure and note the distance from the tip of the bullet to the front face of the cylinder using a digital calliper. Then insert a naked bullet into the same cylinder and gently push forward until the bullet nestles against the cylinder throat. With the bullet held in place measure again the distance between bullet head and the front face of the cylinder. Now calculate the max. cartridge length for this gun and bullet. For initial testing choose an overall length of max. less .010".
Unfortunately, most loading manuals do not highlight the most accurate loads, but tend to concentrate on max. loads. Sometimes they will also give starting loads. The best information can be gleaned from studying match reports and some internet sources are quite useful. Try to identify which powders are most popular with the accuracy crowd. After finding a popular load and after checking with the manuals that the load is not too excessive, make up 5 series of 5 or 10 rounds each with powders charges varying from –10%, -5% , +0% +5% and +10% of chosen load. Start by firing the rounds with the lowest powder charge first and work through to the highest charge in order to identify the powder charge giving best accuracy. In the second stage repeat the test, or fine tune the powder charges to confirm initial testing. Having done this, in the third stage we then alter bullet’s seating depth to see if accuracy can be improved some more. After finishing each shooting session check the cylinder and forcing cone for tell–tale signs of leading. If leading is occurring this does not necessarily mean that chamber pressure is too high or that the bullet alloy is too soft. It sounds like a paradox, but often the bullet alloy is too hard or chamber pressure not high enough. Sometimes switching to a softer alloy or increasing the powder charge by 5 or 10% can work miracles. If you switch alloys from say 16 BHN to about 10 BHN it is often necessary to reduce the powder charge by 5-10% to get the same accuracy as with the harder alloy.
My personal experience with 180 grain cast bullet in BHN = 16 (50% Linotype :50% pure lead) and 7,5 grain 3N37 in my S&W Mod. 27 will lead lightly after 20-30 rounds. This picture shows the leading.
In later testing I found that increasing the powder charge to 8,0 grain eliminated the leading. I now use BHN = 10 alloy ( 20:1 Pb:Sn) and accuracy was improved by backing off to 7,0 grain and no leading to boot
Just to see whether this no leading result was just a pressure effect I repeated the test with BHN = 16 bullets – surprise, surprise I still had leading with BHN = 16! See the leading in the barrel.
For light loads where no minimum requirements on velocity or energy apply concentrate on low bullet weights (BHN range 10-16) and fast burning powders like Bullseye.
For moderate loads where a certain powder factor is required and shooting is usually at 75 feet or less concentrate on heavier bullets (BHN range 10-16) and powders with a medium burning rate like Longshot or 3N37.
For maximum loads at longer distances concentrate on the heaviest bullets (BHN range 16-22) with slow burning pistol powders. If accuracy is not quite there consider the use of gas-check bullets or resorting to Soft Checks or alternatively a shot buffer to eliminate gas cutting.
A Revolver And Cast Bullets
I do not know much about handguns or casting or loading for them. Around 1970 I had a Ruger Blackhawk in 44 Magnum that I shot faithfully every weekend some 300 to 400 rounds. I spent most of my spare time during the week casting and reloading. The load was the Keith 429421 bullet in wheel weights, sized .430" and lubed with the black Lyman lube, Remington 2 1/2 primers and 9 grains of Unique. (The first time I shot that gun, first shot with factory loads, I had cuts on the web of my hand from the hammer, the top of my trigger finger and the top of my second finger from the trigger guard. Bleeding nicely from all.) I had read the Elmer Keith books, and shot a lot from a sitting position, knees up and supporting my hands and the gun, back against a tree or my car. My targets were balloons tied to rocks at 100 to 150 yards.
At other times I've had and shot a Colt New Service in 45 Colt, a S&W M27 with 8 3/8" barrel in 357 Magnum, a M14 in 38 Special, the obligatory Luger and many other revolvers and auto-loading pistols.
A few years ago I bought a nickel-plated well-used M29 with an 8 3/8" barrel and a Simmons 4X scope. I experimented with this revolver and several bullet molds, keeping good records of what I tried and the resulting accuracy.
Summary-Here's what I think I know: Bullets much smaller than the chamber throats lead the barrel on revolvers. Lead in revolver barrels decreases accuracy. Proper size or oversize bullets eliminate leading, and are the easiest way to solve the leading problem. CF Ventures Soft Gas Checks and Cream of Wheat (COW) fillers eliminate leading, at least for slower velocity loads; and shoot with reasonable accuracy. Slower powders reduce leading. Faster loads shoot more accurately than slower loads. At least with SWC bullets.