home made bullet mold

[Jim P.]

I am new to this forum and also new to reloading. I have been a machinist for 35 years. I reloaded about 800 9mm with store bought fmj bullets but I would like to cast some of my own lead bullets and load some of them . It seems all the bullet molds are sold out right now so I would like to make my own. I bought some lee 6 mold handles and a sprue plate. I have a cnc mill to machine the mold and also a tool and cutter grinder to make the cutter. My question is how much bigger do you have to make a mold to allow for shrinkage of the bullet after casting? Im sure I could figure this out by trial and error but I was hoping you guys could help me out here. I would like to cast to powder coat the bullets so is there any real reason to cast lube grooves in the bullet? Could I make them smooth just like a fmj?

[charlie b]

I have no idea about the shrinkage part.

A few mfgs offer smooth/undersize molds for powdercoat or Hitek coating.

Instead of making a cherry for cutting the mold I'd be tempted to machine it directly with a small boring tool. Might need a diamond tool for it to get a good finish.

[GregLaROCHE]

I’m not qualified to answer your question about shrinkage, but I know of a few guys on here who most probably can. Just wait and they will surly respond when they see your post.

The second part about no lube grooves, yes you can cast boolits without lube grooves for powder coating. A lot of people are starting to use plain sided molds for PC and paper patching. Don’t forget you may want to use a gas check, so you would still have to consider that.

Welcome to the forum and good luck.

[ryanmattes]

First, just because it has to be said, bullet design is an art. People have been doing it for decades, and despite modern production methods and tools, still can't make better designs than some of the old standards. My recommendation would be to copy a known good design and go from there.

Some of the current mold makers do make tumble lube and smooth bullet shapes. They'll be slightly heavier, obviously, if you leave out the lube grooves. There's no reason not to, and it would probably make it easier to make the mold, and they'll probably drop out easier.

And from there, I'd say you should start out doing single cavity molds, cast with them, and figure out how they drop. There are undoubtedly many hard lessons to learn starting from scratch, and my approach when doing projects like that is to start with the smallest, simplest, and least expensive thing first, that way I get those mistakes out and learn from them before I get deep into the project with a lot of sunk cost.

Good luck!

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[Jim P.]

I could definitely use a boring tool if the bullet doesnt need any lube grooves.

[Jim P.]

I found a 2 cavity lee mold for 9mm on midways website but by the time I was ready to order it was not available. I was going to cast a few with it and then maybe make a 6 cavity mold. I dont have any molds at all to copy at this point. I would also like to make some penta shaped pins to fit in the mold to make hollow points.

[JM7.7x58]

A mold maker recommendation for how much to oversize.
https://forum.castbulletassoc.org/th...utting-moulds/

[Mal Paso]

9mm should be about .001" bigger plus whatever extra for sizing down with wheel weight alloy.

I pinned a few of my 44 molds that I know to cast .432" and the .433" pin is a good fit and .434" won't go. The mold may expand slightly during casting and shrinkage of antimony alloys isn't huge but cold measurements is what you will be using, hopefully.

[Jim P.]

Thanks for the replies guys. Now does any one know how much the powder coat will increase the size of the bullets? I would like to load these bullets without sizing but that may not be realistic.

[country gent]

At The size of most bullets and lead being a dead metal the expansion shrinkage would be from the blocks. Steel / cast iron a would be minimal maybe .001 at the most, brass next with a little more maybe .0015 and aluminum with the most maybe around .0025. The Machinist hand book will also give expansion ratios you can use to figure ir with.

For a one off mould I would machine to size then cast a few good slugs then lapp to size and finish. This will bring you right to size with the alloy and give a fine finish in the mould.

What machines do you have available in the shop. Another issue is How good of shape are they in. Cutting a mould cavity can be a lot of back and forth in a tight area meaning getting play out will be a problem. Tooling is small and delicate lathe boring and getting the nose shape right is tricky when you cant see in the hole. For a straight sided bullet ( coated PP or core) a form reamer would do the job.

Cnc mill use an old 4 flute end mill and grind the cutter .100 under sized to form. rough drill close to depth and smallest dias. Peck drill down to depth with the form cutter. Then a flat circle pocket out to size with full flood coolant to keep chips washed out. completely finish the blocks before cutting the cavities.

Manual vertical mill ir knee mill. If a double acting vise is available then a cherry ground to size this is the oldest way they were done. You can duplicate the above with a rotary table and setting the blocks up centered on the rotary table, this can be a long set up time tapping the blocks to get them centered, but it also allws the undersized cutter to be used making it an easier way to hold size. Here a fixture with a #2 morse taper t fit the rotary table and square sicket on top with set screws makes getting blocks centered much faster.

CNC lathe a fine boring bar and program for it

Manual lathe. drill cavity in steps to save strain on boring bar. Set up with bar registered on center of cavity and machine to the numbers. here getting the play out is tricky. A igitl read out is a real plus. Another would be to grind a d reamer to form from an end mill step drill close then run it in to depth clearing chips often and then set at depth zero and feed out cutting the form. With cutter backed of you can rough feeding away and finish feed out towards you.

Last and easiest is the cnc edm sinker. Turn up 2 carbon electrodes one finish one rough. you want the rougher under sized by more for more over burn. burn down and the flat pocket program. then the finish electrode and the same with a finishing program.

Finish the blocks before cutting cavities including vent lines. I hsve made them with out vent lines but just a decent fly cutter finish. I start with double thickness + .125 to height and cut to length. square up outside and ends cut handles slots drill all holes and tap needed ones. once this is done I rough spot the cavities in. Split in vertical cut off saw and finish faces. This way the alignment pins are perfect. Install pins and your ready to cut cavities. I use longer pins here to get good true alignment.

If you decide on brass or aluminum materials its not a bad Idea to use steel or stainless bushing on the side pins run in and out of, for longer life.

[BrutalAB]

One of us could measure the diameter the cavities of our aluminum, brass, and iron molds are, to eliminate any math/guessing.


If someone hasnt done it by morning, ill try to do it while im letting my dogs walk.

[P Flados]

I have cut a few mold cavities. All my mold making efforts in recent years have been no lube groove (NLG) style. I have several good profiles for my 327 Fed, several for my 7 TCU, a couple of 30 cal and some heavy 35 cals. Photos below are more or less in order with newest first.

For Christmas, I got myself a four jaw independent chuck for my 7x14 mini lathe to improve my precision when making my own molds. I have had pretty good luck using Lee blank 2 cavity aluminum molds and a simple D reamer made from W1 drill rod. Just buying a few Lee blanks (https://www.titanreloading.com/lee-p...nk-bullet-mold) will let you focus on the important part, cutting cavities. I have gotten some really good finishes by pre-drilling a hole and then running the D reamer in at a low speeds with plenty of lube. And a single NLG D-reamer can be good for a whole range of final bullet lengths / weights.

If you are thinking about making boolits for the 9mm, I would caution you that cast in the 9mm can be tricky. I recommend that you plan on powder coating as it is very likely to decrease the effort needed to finding a solution that does not result in barrel leading. Use of powder coat also allows use of a NLG profile. Going this way greatly reduces effort and improves you chances for happiness with a do it yourself mold.

As someone who had to fight hard to get cast to work in the 9mm, I will say that the Lee 120 TC profile is popular in 9mm by those who have achieved success because it just works.

Speaking as an amateur machinist (me) to a real machinist (you), I would recommend a profile similar to a Lee 120 TC, but with a flat base and no lube grooves. Below are links to a couple of accurate molds that give you an idea of the bullet dimensions that should get you close:

http://www.accuratemolds.com/bullet_...35-117ZR-D.png
http://www.accuratemolds.com/bullet_...35-125EZ-D.png

Now, back to the "9mm is tricky" stuff. If you read up on the subject you will find the most important point is "Fit is King". Undersized cast bullets is probably the biggest problem people have with the 9mm. And I am talking undersized after the bullet is seated in the case. The standard expander plugs leave the case ID too small and the case will size down you bullet during seating. If you have a standard expander plug, just plan of making a custom expander plug that will open up the case to the right ID (generally 0.001" to 0.002" under bullet diameter) for the full depth needed when seating the bullet. Now for the bullets themselves, generally you will want your cast bullets as large as possible and still be able to pass the plunk test with a dummy round. And it is a whole lot easier to size down bullets that are 0.003" oversized than it is to go back an rework a mold to increase your "as cast" diameters.

In support of the above, I recommend you pick your general profile, and turn a dummy bullet or two out of something no softer than aluminum. First drill & thread a through hole in 10-24 or 10-32 so you can easily pull it out of a case and so you can easily re-mount it in a lathe. Start with an OD of say 0.358". Seat it in a sized and lightly flared case (caution - headstamps do matter and some brass is thicker than others). Run it through your seater die if needed just enough to remove any remaining flare. See if it will freely slide into you chamber and "plunk" into the fully chambered position. If it does not plunk, figure out why. It could be the case is too big, or you could be getting bullet contact up in the throat. If you have a throat problem, either increase seating depth or remove bullet material as needed to fix it. If you get 0.358" to "plunk," this is what you should try for in way of finished bullets. If 0.358" is too snug, try 0.3575". Repeat as needed to find what diameter works in your gun. If you have more than one gun, check out all of your guns to see what will make them happy.

Lets say you find that 0.3575" is your largest size to pass the preliminary plunk testing above. I would actually shoot for as cast bullet diameters of around 0.358". The PC will add a little diameter, but bullets seem to work better when sized down some. In my opinion, sizing down 0.002" or 0.003" is better than anything under 0.0015".

[JM7.7x58]

I have cut a few mold cavities. All my mold making efforts in recent years have been no lube groove (NLG) style. I have several good profiles for my 327 Fed, several for my 7 TCU, a couple of 30 cal and some heavy 35 cals. Photos below are more or less in order with newest first.

For Christmas, I got myself a four jaw independent chuck for my 7x14 mini lathe to improve my precision when making my own molds. I have had pretty good luck using Lee blank 2 cavity aluminum molds and a simple D reamer made from W1 drill rod. Just buying a few Lee blanks (https://www.titanreloading.com/lee-p...nk-bullet-mold) will let you focus on the important part, cutting cavities. I have gotten some really good finishes by pre-drilling a hole and then running the D reamer in at a low speeds with plenty of lube. And a single NLG D-reamer can be good for a whole range of final bullet lengths / weights.

If you are thinking about making boolits for the 9mm, I would caution you that cast in the 9mm can be tricky. I recommend that you plan on powder coating as it is very likely to decrease the effort needed to finding a solution that does not result in barrel leading. Use of powder coat also allows use of a NLG profile. Going this way greatly reduces effort and improves you chances for happiness with a do it yourself mold.

As someone who had to fight hard to get cast to work in the 9mm, I will say that the Lee 120 TC profile is popular in 9mm by those who have achieved success because it just works.

Speaking as an amateur machinist (me) to a real machinist (you), I would recommend a profile similar to a Lee 120 TC, but with a flat base and no lube grooves. Below are links to a couple of accurate molds that give you an idea of the bullet dimensions that should get you close:

http://www.accuratemolds.com/bullet_...35-117ZR-D.png
http://www.accuratemolds.com/bullet_...35-125EZ-D.png

Now, back to the "9mm is tricky" stuff. If you read up on the subject you will find the most important point is "Fit is King". Undersized cast bullets is probably the biggest problem people have with the 9mm. And I am talking undersized after the bullet is seated in the case. The standard expander plugs leave the case ID too small and the case will size down you bullet during seating. If you have a standard expander plug, just plan of making a custom expander plug the will open up the case to the right ID (generally 0.001" to 0.002" under bullet diameter) for the full depth needed when seating the bullet. Now for the bullets themselves, generally you will want your cast bullets as large as possible and still be able to pass the plunk test with a dummy round. And it is a whole lot easier to size down bullets that are 0.003" oversized than it is to go back an rework a mold to increase your "as cast" diameters.

In support of the above, I recommend you pick your general profile, and turn a dummy bullet or two out of something no softer than aluminum. First drill & thread a through hole in 10-24 or 10-32 so you can easily pull it out of a case and so you can easily re-mount it in a lathe. Start with an OD of say 0.358". Seat it in a sized and lightly flared case (caution - headstamps do matter and some brass is thicker than others). Run it through you seater die if needed just enough to remove any remaining flare. See if it will freely slide into you chamber and "plunk" into the fully chambered position. If it does not plunk, figure out why. It could be the case is too big, or you could be getting bullet contact up in the throat. If you have a throat problem, either increase seating depth or remove bullet material as needed to fix it. If you get 0.358" to "plunk," this is what you should try for in way of finished bullets. If 0.358" is too snug, try 0.3575". Repeat as needed to find what diameter works in your gun. If you have more than one gun, check out all of your guns to see what will make them happy.

Lets say you find that 0.3575" is your largest size to pass the preliminary plunk testing above. I would actually shoot for as cast bullet diameters of around 0.358". The PC will add a little diameter, but bullets seem to work better when sized down some. In my opinion, sizing down 0.002" or 0.003" is better than anything under 0.0015".

That was a great post!
Thanks
JM

[P Flados]

I just noted that you already purchased the 6-cav handles and sprue plate. I also remembered a few more things worth suggesting.

You may be able to find 6 cavity blanks in stock somewhere, but everywhere I looked is out of stock right now.

I really do recommend just getting 2 or 3 Lee 2 cavity blank kits to start off with. If you pay attention to what you are doing, a 2 cavity lee blank can be made into a 3 or 4 cavity mold depending on bullet size. If you want to do this you can intentionally offset the cavity just a little with the sprue closer to one edge of the cavity for the factory sprue holes.

After you have used some of the Lee blank kits, it will probably be easier to make some mold blocks from scratch. I do not use the press in pins for my Lee 2 cavity blanks. I use something that will allow disassembly in case I want to do a re-work or in case the mold block does not work out and I want to re-use the handles.

For a lot of my made at home molds, I have mixed cavities. For example you could have one mold that drops a 110 and one that drops a 120 and one that drops a 130. When trying to find what a gun likes, this method allows a easy way to try a bunch of different stuff. For me, getting multiple cavities to drop the same weight has been a lot more effort than just going with an intentional mix in sizes. If you do go with an intentional mix, having different bullets where the only change is a small length difference makes sorting you cast bullets more of a challenge. Having a mix in both weight and style (round nose vs flat nose or small vs large meplat for examples) makes sorting easier.

Sooner or later the crazy demand for bullet molds will fade some and you can either buy a ready to use 6 cavity (one of the great bargains of the casting world) of a 6 cavity blank. You can do a backorder directly for the blank from the Lee site if you want one asap and want to pay more than Titan charges.

[P Flados]

P FLADOS Good post. A lot of molds are worn out and if you could find a smaller mold than what you need it would save a lot of time. Like boring a motor.

If you want big and long bullets, re-using is easier. I seem to be moving down in size and have had minimal re-use opportunities.

[Traffer]

This is the shape I would recommend for a 9mm. It is from the Lee 120gn mold. You can lose the grease grooves. But keep the step at the start of the ogive. It is necessary for the cartridges to chamber in most guns. It may be easier to cut these by cutting the ogive with the narrower diameter all the way and reaming it to the base diameter. Just stop where you want to start the ogive. I am not a machinist. But I have been playing with making swaging dies for these little beasties.

[Jim P.]

Thanks for all the replies guys. I am the shop manager so I have access to all the machines. We only have 2 cnc machines. A mazak cnc mill with 6000 rpm spindle and we have a large cnc lathe but it is kind of big for machining a mold. It will swing 30" inches inb diameter x 14 feet long. I would prefer to use the cnc mill. I also have a hurco cnc mill here at home. I think I will make my mold large enough for 6 cavities but just machine one cavity for now. I will start small and cast a few bullets and powder coat them and see what size I am getting. I can always put the mold back on the mill and indicate the hole in and recut it if I have to. I can still use the same tool, just program the circular interpolation a little bigger. once I figure out what works, I can machine more cavities. A cnc is easy to make more cavities once you figure out the program. It will make all the cavities the same. I used to do some tool grinding at one time and still have the machines so making a tool will not really be a problem.

[Traffer]

Thanks for all the replies guys. I am the shop manager so I have access to all the machines. We only have 2 cnc machines. A mazak cnc mill with 6000 rpm spindle and we have a large cnc lathe but it is kind of big for machining a mold. It will swing 30" inches inb diameter x 14 feet long. I would prefer to use the cnc mill. I also have a hurco cnc mill here at home. I think I will make my mold large enough for 6 cavities but just machine one cavity for now. I will start small and cast a few bullets and powder coat them and see what size I am getting. I can always put the mold back on the mill and indicate the hole in and recut it if I have to. I can still use the same tool, just program the circular interpolation a little bigger. once I figure out what works, I can machine more cavities. A cnc is easy to make more cavities once you figure out the program. It will make all the cavities the same. I used to do some tool grinding at one time and still have the machines so making a tool will not really be a problem.

Many people size their bullets after powder coating. When that is done, allowing for the exact thickness of powder coat is not necessary. In fact powder coat varies a great deal in thickness. It even varies from one batch to another a lot of times. It should be no problem for you to turn a sizing die. Many folks make them from 7/8- 14 bolts.

[owejia]

Old retired machinist here, with the tool and cutter grinder available you can grind your tooling to about any configuration you want to experiment with. As far as shrinkage, kinda depends on the alloy used, mold material, casting temp. As you can see there are a lot of variables that can change things. I pc all my boolits but I always size them as needed depending on what I'm shooting them in. Nose profile is important in feeding from a magazine, but not as important as using in revolvers. A lot to keep you thinking about as you pursue this hobby. Good luck.

[Burnt Fingers]

Molds are available at regular prices.

NOE
MP
Arsenal
Accurate

The first three can have a mold in your hands within a week to 10 days.

The fourth might take 2-3 weeks.