Excerpt from Fouing Shot 143 Jan/Feb 2000

By David Southall

Bonita Springs, FL

My earliest experiments using cast bullets were fairly successful, using unsized bullets and bee’s wax/lard finger-applied as a lubricant. The only real problem I encountered was the occasional large bullet that prevented chambering. Some time later, I invested in a Lyman “push-through” die, which fit my Lyman 310 tool. No longer did an oversize bullet give me trouble! Back then I was shooting .32-20 and .44-40 Winchesters, at black powder velocities and pressures.

Over time, I accumulated more firearms, and was introduced to the Lee Precision line of very inexpensive bullet molds and reloading equipment. With each new gun, I would “invest” in a mold and sizing die so that I could shoot reduced loads cheaply. Wheel weight metal and Alox/beeswax lube was a pretty good combination for both handgun and moderate velocity rifle loads.

Gleaning technical (but not always helpful) information from gun magazines, kept my interest level high, as I experimented with alloys, hardness, powders and primers. In short order I had developed several loads which met and even occasionally exceeded my expectations. Once I had that near-minute-of-angle load, I wanted make up a lot of them. Here is where my troubles began.

The principal bottleneck in the production of the copious quantities of accurate cast-bullet handloads was laboriously hand lubricating each bullet before it was pushed through the press-mounted, Lee sizing die. This was messy, and time-consuming. In addition, the gas check on some bullets slid back on the check shank as they were pushed through nose first in the Lee die. A lubri-sizer would make this operation simple, and fast. I bought the RCBS model, noting its similarity to Lyman’s, but with sturdier linkage. I also bought several different sizing dies and nose punches, and set to work making up a large volume of sized and lubed bullets.

Expecting that these “machine-quality” bullets would actually be superior to those manually lubed bullets, I was surprised when they weren’t. In fact, group size opened up to 4-5 inches. I looked frantically for the cause. They were the correct size, hardness, alloy, weight, with gas-check properly seated - everything seemed the same. I weighed a couple of hundred, separating them into 1/10 grain lots and shot them carefully. There was no improvement in the accuracy of these either.

While carefully inspecting one of the lubri-sized bullets under magnification, I noticed a slight difference in the width of the sized portion of the ogive, above the first lube groove. Looking at several others, it appeared that at least some of the bullets were not entering the sizing die straight. I took a look at a few bullets that had been sized in the Lee push-through die, and the first band was perfectly uniform, all around.

Excerpt from Fouling Shot 143 Jan/Feb 2000.



Recently, there have been a handful of articles in The Cast Bullet addressing the concept of “lube pumping”. I have learned a great deal from these articles, and I’d like to thank the authors for sharing their thinking with us. In short, their conclusions have been that bullet lube is not just rubbed off of the bullet and onto the barrel, but rather is delivered from the lube groove to the bore via a combination of several mechanisms, including the linear acceleration of the bullet down the bore, the centrifugal acceleration arising from the spin of the bullet after engraving, and the compression of the bullet during firing and the concomitant shrinkage of the groove itself. Without a doubt, each of these mechanisms plays a role, although the magnitude of each of these contributions probably changes as a function of pressure, velocity, alloy hardness, bullet diameter, etc. These concepts also correlate nicely with the research done by the NRA decades ago in which it was the bullet lube’s flow characteristics were found to be important, not necessarily it’s lubricating ability.

I’d like to throw another possible mechanism for delivery of lube from the bullet to the bore out on the table for people to consider. In high-speed photography of a gun being fired, the first thing one sees is a puff of smoke (or even small flames) escaping from the muzzle, significantly preceding the emergence of the bullet from the barrel. This is due to gas blow-by, both from leakage around the bullet in the throat (i.e. pre-engraving) and leakage around the bullet while traversing the barrel (i.e. post-engraving).

Engraving is a brutal process. Bullet metal is distorted and abraded away, and the bullet’s surface undergoes a constant metamorphosis as it travels down the bore. In addition, there are microscopic imperfections in the grooves and lands of the bore. The combination of these microscopic defects creates channels that allow the high pressure gases to escape. These gas molecules are very small (thousands will fit into a defect only .0001” wide), and very hot, and the pressure gradient from the base of the bullet to the first lube groove is extremely high. As soon as these gases reach a lube groove, the lubricant within that groove is subjected to extremely high pressure and temperature. Since the net flow of gas is from the base of the bullet forward, the melted lube is forced forward, precisely where it is needed (the other lube pumping mechanisms leave the lube in the wake of the bullet).

I did a simple little experiment that I feel lends strong support to the concept of bullet obturation, without the complications due to bullet impact. Here’s what I did; using the RCBS 45-255 Keith SWC mould, I cast a batch of bullets with wheelweight alloy (plus a small amount of tin), and a second batch from linotype. The first batch weighed an average of 266grains and the linotype bullets weighed in at 255 grains. All bullets were sized .452” and lubed withmy homemade moly lube (equal parts beeswax and Sta-Lube Extreme PressureMoly-Graph Multi-Purpose Grease). Allbullets were loaded over 9.0 grains of Universal Clays into W-W cases, andprimed with Federal 150 primers. Allchronographing was done within a 1 hour period, under virtually constantweather conditions. The results aresummarized in Table 1.

One last bit of “howling at the moon”, and what better way to purge the system than to talk about cleaning? As cast bullet shooters, we are constantly working towards that mythical perfect combination of mould, alloy, lube, powder, case and primer that will give us the accuracy and ballistics we desire.... and do it with no leading! Unfortunately, leading is something we cast bullet shooters have to deal with; sometimes only occasionally, sometimes more often.

Many different solutions have been put forward for removing lead deposits from a prized barrel. One that has worked well for me was laid out by Veral Smith in his book on cast bullets. This approach involves cutting off a strip from a copper or brass scrubbing pad and wrapping it around a bore brush. If you’ve never tried this approach for removing leading, you should — it is absolutely amazing! A few strokes and the lead is gone! The drawback to this method is that brass scrubbing pads require a pair of scissors to cut off a piece, and when you do cut it little pieces go flying every which way (which isn’t real popular with either spouses or pets). A much simpler approach, and one that is just as effective, is to replace the scrub pads with bronze wool (not steel wool; bronze wool is available at the larger hardware stores).

I wrap a wet patch around a bronze bore brush and swabout the barrel to first loosen up the powder fouling. Next, I wrap a pinch ofbronze wool around this dirty patch and run it back through the barrel a fewtimes. The bronze wool cuts the leadfouling and the wet patch snags the pieces. Peel off the patch and bronze wool and discard. Wrap a fresh, dry patch around the bore brush and swab out the remaining solvent and fouling. Using this method, it is possible to clean even a heavily leaded barrel in less time than it took to read this description. Less time spent cleaning means more time for casting, loading, shooting and hunting. I like it like that!

Bullet moulds, regardless of the material they are made of, are all pieces of precision equipment that are subject to wear, abuse and the elements. Handled incorrectly moulds are easily damaged and while certain components the likes of screws and sprue plates may be replaced any damage to the cavity in which the bullet is formed is not so easily corrected. Likewise, light, surface rust can easily be removed but years of neglect and long term corrosion can be a challenge to remedy. That said, a surprising number of simple fixes can be put into to play to make a mould serviceable again and similarly some straight forward modifications or alterations may be made to moulds. Let’s address each individually.

Maintanence – break in.

RUST.

Light rust may easily be removed from the surface of a mould or sprue plate by using very fine steel wool and oil. Care should be taken around the crisp edges of the bullet cavity so as not to round off any corners. For a gentle, elbow grease free approach to rust removal try emerging the mould in apple cider vinegar or covering it with a paste made from baking soda and lemon juice. Either substance will remove the rust in short order and do so without major expense or harm to the environment. For rust in the bullet cavity the best removal is to polish it out by coating a bullet in very fine abrasive compound and rotating the bullet in the mould. Take a bullet and place it in the mould and via the hole in the sprue plate drill a centred hole in the base of the bullet. Remove the bullet from the mould and wind a suitable screw into the newly drilled hole and coat the bullet in car paint work cutting compound or even tooth paste. Place the shank of the screw in a cordless drill and put the bullet back into the mould. Holding the two halves of the mould together firmly with one hand SLOWLY operate the drill in the other hand to rotate the bullet in the cavity. This rotating action in conjunction with the very fine abrasive will polish out the rust but care should be taken to work SLOWLY and check the cavity often. Don’t be too concerned about enlarging the cavity as this takes a lot of work even on a relatively soft aluminium mould.

OUT OF ALIGNMENT.

I have a Lyman 311008 double cavity mould for my .32-20 Martini. Some years back the mould started producing bullets that were far from round. In on dimension the bullets measured .310 inch and 90 degrees to this .315 inch. The problem on closer inspection was the second hand mould had sustained a bit of abuse of the years and the alignment pins were not engaging properly. The pins protrude from one half of the mould (male side) and mate with holes in the opposite half (female side) however due to some ‘stout’ usage the leading edges of the alignment pin holes had been chamfered and now the pins, when engaged, were a sloppy fit. This remedy this problem take the half the mould with the pins in, lay it cavity side down on a piece of hard wood in which holes matching the pins have been drilled and gentle tap the back of the pins to push them further out on the cavity side. Surprisingly little movement is required; perhaps 0.010 inch. The pins then protrude more and engage fully on the female side of the mould. Alignment corrected. Depending on previous history it may also be necessary to take a countersink tool and resurface the leading edges of the female side into which the pins engage.

SPRUE PLATE TUNING.

The sprue plate is a particularly critical part of the mould and with the exception of nose pour moulds it is this humble piece of metal that creates a perfectly square base on your bullet. Of course the role is the sprue plate is also to cut the sprue from the formed bullet prior to removal from the mould however if the plate is not perpendicular to the bullet cavity axis the base of the bullet will not be square and this will lead to inaccuracy. Sprue plates should be dead flat and mate perfectly to the top of the mould. I tune all my sprue plates such that when held up to a strong light little or no gap between the top of the mould and the underside of the plate may be seen. This is achieved by honing the underside of the plate to remove high spots and to match the mould. DO NOT be fooled into thinking you can generate a perfect match between the two by over tightening the sprue plate screw as you will just ruin the mould/screw/plate.

Start by removing the plate from the mould. Find a dead flat surface to work on – an old sheet of glass can be useful or a drill press table. Take some 300 grit abrasive paper and lay it on the surface then with even pressure on the sprue plate begin polishing. This process will remove any high spots on the surface of the plate at which time wipe the surface to remove all particles and place back on the mould to check progress. If the mould is raised on one edge when in place on the mould with the retaining screw tightened to usual operating tension, remove the plate once again and remove material from the opposite edge. Of course much care should be taken but don’t be put off. I use very fine files and with the draw filing process work areas of excess material prior to final polishing. Again care should be taken to work SLOWLY and check progress OFTEN. Continue until the plate, under the usual amount of screw tension or operation, is mated perfectly to the mould and no light can be seen between the surfaces.

At risk of making the reader squirm I have even been known to polish the top of a mould in order to remove any high spots. Remember this. Your mould, if from a major manufacturer, is a mass produced product and will not be perfect.

VENTING.

All modern moulds have tiny little lines cut into the internal faces that act as vents to allow air to escape the mould as molten alloy is poured in. Without these vents the air becomes trapped in the mould and prevents 100% bullet fill out. Lee aluminium moulds are renown for poor venting and often benefit from a the use of a carbide scribe to ever so slightly increase the depth of the venting lines. Working from the cavity towards the outer edge of the mould CAREFULLY draw the scribe down the length of the venting line. Do NOT draw the scribe towards the cavity as you will create a burr at the edge of the vent where it enters the mould and this will prevent your bullets dropping freely. The upwards pointing lines are the ones to focus on as hot air rises and to begin with only every second line need be worked. With steel or brass moulds inspect the vent lines to ensure they are free of obstructions and should material be present very gently pick it out using copper/brass wire so as not to damage the mould. If the venting lines on your steel or brass mould are not well define follow the instructions for the Lee moulds above.