CNC A PC program takes the customer's specs and turns it into CNC code, then a A CNC (computer controlled) lathe bores the bullet cavity. The software allows the bullet design to be customized, within certain limitations, without having to make a custom cherry or a custom form cutter.
Standard Block Dimensions 1.5"W x 1.5"H x 1.75"L. These blocks are optimal for bullets in the 180 - 300 grain range, depending on alloy. 300 to 425 grain bullets are sometimes made in these blocks but heat-related fill problems may occur, depending on alloy, mold material, and casting technique. As a single cavity, the standard block cast well with 400 - 700 grain bullets. Use RCBS handles or Lee 6-cavity handles. Lyman/Saeco handles may be modified to fit.
XL Block Dimensions 1.5"W x 1.5"H x 2.25"L. The XL blocks are mandatory for 2-cavity 50 caliber molds. In addition, the XL blocks may be a prudent option for any bullet over 300 grains. Use RCBS handles or Lee 6-cavity handles. Lyman/Saeco handles may be modified to fit.
Machine-cast Block Dimensions 1.32"W x 1.5"H x 1.8"L. They are drilled and tapped to accept Magma hardware and sprue plate (not included). Conventional handles will not fit.
Handles are not included.
Aluminum 2024 aircraft alloy is light weight, corrosion resistant, and easy to machine. Aluminum seems to be better than other materials at avoiding overheating problems when casting very large bullets. On the down side, all aluminum alloys loose much of their strength at bullet-casting temperatures, although 2024 is better than most in that regard, and it will outlast most of us if handled carefully.
Brass 360 brass resists corrosion and machines beautifully. Brass has the highest thermal conductivity of any of the mold materials, which sounds good in theory but doesn't seem to make a darned bit of difference in practice. On the downside, brass is heavy. Being cold rolled, it does have residual stresses and it can warp a tiny bit after machining, though very rarely does it warp enough to create a noticeable problem with standard size blocks. However, because of the warping and the weight, I do not use brass for XL blocks. Also, I do not recommend brass for black powder applications, since the high casting temperatures make it more prone to warp.
Ductile Iron Iron is a very stable material that is resistant to warping. There are many different types of iron, and not all are suitable for molds. We need something that is strong, but not brittle, and easy to machine, yet wear-resistant. The alloy that I am using at the moment, 65-45-12, is as strong as steel but noticeably easier to lathe bore. While it's yield strength is only 45,000 psi, it does maintain practically all of its strength at casting temperature, and also, it is much stronger in compression -- 110,000 psi. On the downside, it is very susceptible to corrosion. Iron is also more susceptible to overheating compared to aluminum. Iron molds cost more because the raw material comes in rough, oversize pieces that require quite a bit of milling. Also, it takes twice as long to lathe bore compared to aluminum or brass.
Meehanite I do not offer Meehanite blocks and here is why. To begin with, Meehanite is not a type of iron, it is a type of foundry process that is used with a variety of irons, so when someone says that something is made of Meehanite, that really doesn't tell you a darned thing. The Meehanite process is licensed so if you want Meehanite you have to work with with a licensed Meehanite foundry. Supposedly, iron made with the Meehanite process is more fine grained and uniform than the same alloy made with a non-Meehanite process, and while that may be important for some applications, I'm not sure that it is a big deal for mold blocks. Once upon a time, Meehanite was used by several mold makers but I can find no mention of the word "Meehanite" in their current advertising. The bottom line is, while I have nothing against Meehanite, it is not readily available.
| Material | Yield Strength psi |
Strength at 500°F psi |
Melting Temperature | Coefficient of thermal expansion in/(in °F) x 10-6 |
Thermal Conductivity Btu/hr-ft-°F |
|---|---|---|---|---|---|
| 2024 T4 Aluminum |
45,000 | 9,500 | 935° F | 13 | 70 - 110 |
| 360 Brass cold rolled |
45,000 | ? | 1650° F | 11.8 | 67 - 85 |
| 65-45-12 Ductile Iron |
45,000 | nearly 45,000 |
? | 6.4 | 18.7 |
Sprue Plates are made from 1/4" heat treated 4140 steel.
Alignment 304 or 303 stainless steel male/female bushings are used on aluminum and brass blocks. Hardened tool steel male/female bushings are used on iron blocks.
Ventilation Vent lines are cut on both halves of the block. I have made several unvented molds for my own use that cast as well as any other, but some alloys show a distinct preference for aggressive venting, especially at higher mold temperatures.