# Custom Bullet Mold



## jbolt (Jul 31, 2018)

So finally getting to projects that make things other than tools and equipment.

I'm posting this in the projects area since it involves making a custom form tool.

I shoot a sport called Metallic Silhouette which is shot off-hand (standing) with no support, slings or special clothing. Targets are metal silhouettes of chickens, pigs, turkeys and rams set an different distances. There are several disciplines ranging from air rifles with targets out to 60 meters and high power out to 500 meters. One of the disciplines I shoot is lever action pistol cartridge with a .357 lever action rifle. I cast and shoot lead bullets with this rifle. Most commercial molds for the .357 are wad cutters or semi-wad cutters. I have not found a commercial mold with a round nose that can be gas checked. Pistol cartridge silhouette is out to 100 meters and a few of the commercial semi-wad cutter designs do well but I wanted something with a better ballistic coefficient.

There are several companies that will make custom molds from your designs but they can cost $200-$300 per mold. I set about to make my own. Lee Precision offers mold blanks that come with handles so I ordered a pair of those to get started. Lee Precision also has a guide sheet for creating drawings for them to make custom molds for customers. Armed with this info I set about designing a bullet.

This is the final design. These will be powder coated so I chose to use the Lee small lube grooves instead of a large lube groove or no lube groove. The theory is the bullets will be run through a final sizing die and I wanted the body to have a little room to compress without elongating the bullet if it had no grooves while keeping a larger surface area for barrel land engagement. The target weight with range lead & gas check is 155-160 grains.




To cut the mold I decided to make a one flute form tool from O-1 drill rod. Several HSS tool bits were needed to cut the various grooves and nose profile.

Tools from left to right are (1) basic turning/facing tool. (2) Nose form tool. This tool has a double radius, .075 at the tip and .312 beyond. I printed the profile at full scale, glued it to the tool bit blank and rough ground by hand on the bench grinder. Finishing was with a diamond bit in a die grinder. (3) Case crimp groove tool at 15 deg with a 90. (4) Lube groove tool, each side is 26 deg. (5) gas check relief tool at 3 deg.




1/2" drill rod turned to .359" ready for the nose form.




Nose profile cut.




Hand sanded w/320 to .358"




Crimp groove cut




Lube grooves cut




Gas check relief cut




Final profile


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## jbolt (Jul 31, 2018)

Off to the mill. First order of business is to remove half the diameter. I left .002" for final honing. Note the adjustable parallel under the toll to discourage any deflection.




Next is the side relief cut. I left as much as possible to maximize the strength.





Next was to hand grind the rest of the reliefs. Not pretty but it does the job.




At this point I hand honed the flat of the cutting edge on a 400 and 1000 grit water stone to remove any burrs at the cutting edge.

The tool was heat treated and tempered to approx 62C if I did everything correctly. I used the Brownells anti-scale powder for the first time on this part and was pleased with the result. It could be a little better but being the first time use I was not sure on the best procedure for applying the powder. The steel needs to be heated to 500 deg and then coated. I ended up with a few spots where it was too thick which cracked and spalled off during heat treating.




The tool is now hard. The edge held through the heat treating so no need for further honing.


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## jbolt (Jul 31, 2018)

To cut the mold I made a tool holder from a 1" square aluminum bar held in a tool post holder. The aluminum wad drilled and reamed in the tool holder using the lathe chuck for drilling and reaming. This ensured the form tool would be on center and established the zero or final cut dimension. A couple of 10-32 screws in the side of the aluminum lock the form tool in place. I also turned a centering tool out of the same drill rod to use in the tool holder to assist is aligning the mold to the cutter.

Reaming the tool holder.




To hold the mold halves I modified some soft jaws for my 3-jaw chuck to replace two of the jaws on my 4-jaw chuck. This is exactly why I purchased a 4-jaw chuck with two-piece jaws.

Here is the mold aligned and pre-drilled ready for cutting the profile with the form tool. 




The form tool was set to plunge cut the minimum bore diameter of the largest bullet groove and then advanced .03" at a time then cleared of chips until I got to the end of the pre-drilled portion. I then advanced in .01" increments with the final depth in a couple of .005" increments. Once the depth was cut the form tool was advanced into the side of the bore to create the grooves. Total side depth is .016" which was cut in three steps.

I only cut one cavity for now. I will now cast some bullets to verify they cast at the correct diameter and will accept gas checks. 




Ready to cast some bullets.


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## MarkDavis (Jul 31, 2018)

Nice pictures and pointers.
The adjustable parallel under the reamer during cutting really caught my attention.
Thanks


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## pontiac428 (Jul 31, 2018)

Very cool, thank you for sharing.


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## jbolt (Jul 31, 2018)

The first run was not successful. The bullet is .013" under size and the groves are not well defined. I'm going to attempt to re-cut the same cavity. 

I just don't have a good way of measuring the cavity with the grooves. My smallest bore gauge only goes down to .350' and the minimum ID for the crimp groove is .326".  I may have to get a set of pin gauges.


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## MarkDavis (Jul 31, 2018)

Maybe just take a piece of aluminum and turn it to lube groove diameter for use as a gauge.
Or .001 under.
I would be pretty hesitant to stick a steel pin gauge in an aluminum mold.


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## pontiac428 (Jul 31, 2018)

Could it be your cavity cutter?  I think if you cut the tool like a single-flute reamer you may be able to keep the groove definition.  I didn't realize the first read through that you removed a lot of material from the back side of the cutter for clearance.  How is the roundness?  Looks like you did a good job with the mold blocks, I imagine they're going to come out nice and round.


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## mattthemuppet2 (Jul 31, 2018)

for holes under 0.5", use a small hole gauge. similar idea to bore gauges, but consist of 2 rounded fingers that are forced apart by a cone. They come in sets of 4 from 0.125 to 0.5". Super handy for small holes


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## jbolt (Aug 1, 2018)

MarkDavis said:


> Maybe just take a piece of aluminum and turn it to lube groove diameter for use as a gauge.
> Or .001 under.
> I would be pretty hesitant to stick a steel pin gauge in an aluminum mold.



A steel pin is not a problem as long as you are not forcing it. Aluminum is sticky so aluminum on aluminum is probably not the best way to go. If one was concerned about marring, a brass or bronze pin would be better.

The more I thought about it a pin gauge will only tell me what the minimum bore diameter is. I would be assuming the groove diameter is correct without ever having measured it since I have no way to do that with the basic measuring tools I have. The neutral rake form cutters used to make the grooves may not be cutting to the actual depth shown on the digital readout.


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## jbolt (Aug 1, 2018)

pontiac428 said:


> Could it be your cavity cutter?  I think if you cut the tool like a single-flute reamer you may be able to keep the groove definition.  I didn't realize the first read through that you removed a lot of material from the back side of the cutter for clearance.  How is the roundness?  Looks like you did a good job with the mold blocks, I imagine they're going to come out nice and round.



I tried re-cutting the cavity and discovered some errors on my part. First, when I did the initial plunge cut I failed to account for the DRO being set for diameter and did not account for that so the minimum bore was cut over size from the get go. This explained for the loss in definition of the grooves but did not account for the cavity being under size. When re-cutting I also found the relief grind toward the base of the bullet was not deep enough and interfering not allowing the cutter to engage further. It also flared the base of the mold.

At that point I took a good look at the cutting tool and re-honed the edge, improved the relief and did some fine detailing with a rotary tool to improve the cutting edge. After that I cut another cavity. This time I paid better attention to how the cutter was performing and found that with the large neutral rake cutting edge the cutter has about .002 of spring. This time I ran the final cut several times allowing for the spring of the tool until no additional material was removed and I could feel the cutter just starting to make contact at the final dimension. During the final dimension cuts I would let the cutter dwell on the part for 2-3 minutes at a time before clearing, cleaning, lubing and repeating. I did that about eight times I think before I felt it was fully cut. I didn't have time to cast any last night so I will try today and if it is still under size I now have a better feel on how much more I would need to cut.

Here is the second cavity. You can see the groove definition is much better.


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## jbolt (Aug 1, 2018)

mattthemuppet2 said:


> for holes under 0.5", use a small hole gauge. similar idea to bore gauges, but consist of 2 rounded fingers that are forced apart by a cone. They come in sets of 4 from 0.125 to 0.5". Super handy for small holes



That is an interesting idea. It would be difficult to try and measure the peak of a tapered cut but I suppose you could preset the hole gauge to a dimension and use it as a feeler gauge.


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## mattthemuppet2 (Aug 1, 2018)

yes, they have the same disadvantages as bore gauges, but they are smaller at least! For gauging the bottoms of the valleys I think your only option is to make a form gauge (like a thread gauge) and use that.


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## jbolt (Aug 2, 2018)

First casting came out .004" under size so I put it back in the lathe and recut it to the correct size. These came out as I was expecting. 
	

	
	
		
		

		
			








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## mattthemuppet2 (Aug 2, 2018)

nice! How do you QC them, short of firing them out of a gun? I assume that any small variations in the casting process (fill, voids, I dunno) will have a large effect on the ballistics?


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## jbolt (Aug 2, 2018)

For competition use bullets are sorted by weight. Being made from scrap lead pulled off the berm at the range the alloy composition can vary which affects mold fill out, weight and hardness. Voids are uncommon but can happen.

Ballistics is a little more complicated but in general terms is a function of bullet weight, length, shape, velocity, spin and barrel length. At distance some other factors are altitude density and angle. Being a pistol cartridge bullet the effective range out of a riffle is around 200 yards. A flat faced wad cutter type bullet will obviously be much less due to the high drag but these are intended for short distance use.


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## mattthemuppet2 (Aug 3, 2018)

cool, thanks for the info. I'm guessing "grains" is the unit of weight used?


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## shooter123456 (Aug 3, 2018)

mattthemuppet2 said:


> cool, thanks for the info. I'm guessing "grains" is the unit of weight used?


Yes, it is common for measuring powder and bullets.  1 grain is 1/7000 of a lb.


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## MarkDavis (Aug 3, 2018)

Matt,
A bullet mold will usually get better with use, it takes a few heat/cool cycles to cook all the cutting coolant out of the blocks, and sometimes little quirks with temperature of the melt, and time timing of casting, help make pretty uniform bullets.
That second bullet looks pretty good coming from a fresh cut cavity.

If you really want to fall in bullet casting hole, check out castboolits@gunloads.com


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## jbolt (Aug 4, 2018)

MarkDavis said:


> That second bullet looks pretty good coming from a fresh cut cavity.



The last photo with the two bullets, the top bullet is from the first cavity which was over bored, the bottom bullet is from the second cavity which was done correctly. It was a side by side comparison I failed to describe.

I scrubbed the mold in hot water and dish soap after machining and then soot the mold cavity with a wood match. It takes about 10-20 castings to get the mold temp right before dropping good bullets.


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## T Bredehoft (Aug 4, 2018)

I guess the question to ask is "How do they shoot?"


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## jbolt (Aug 4, 2018)

T Bredehoft said:


> I guess the question to ask is "How do they shoot?"


I will find out on wednesday.

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## jbolt (Aug 6, 2018)

On the second cavity of the mold the bullets cast at .361". For traditional lubing this would be fine as they are pushed through a .358 sizing die for final sizing. Being my first stab at using powder coating as a lube medium I found that it added .003" to the diameter. This is a little too much for the sizing process and was removing some of the powder coat.

I decided to go ahead and cut my second mold to a size allowing for the powder coat. I did pick up a set of pin gauges so I found the largest pin that would fit the bore of the over size mold and then cut the other mold to .004" less using the smaller pin as a reference.

Here is the second mold block with both cavities cut. 




The bullets out of this mold cast at .357" and with powder coat finish at .360" which worked perfect for sizing.

Here is a small batch of completed bullets with gas checks ready for testing. I will do load testing this Wednesday. I'm hopeful the powder coating will work out. If so then I will be able to use the bullet feeder on my progressive reloading press and no more concerns with handling raw lead or sticky lube.


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## jbolt (Aug 9, 2018)

First tests are promising. They shoot a little different than lubed bullets and seem to like a higher velocity. With the powder I use, between 13 and 14 grains has been the sweet spot with other bullets of this weight so I did my test loads within that range. This bullet started to come alive at the max load I had done which was 14 grains.

This is at 100 meters. Rossi M92 w/24" barrel resting on a front bag, peep sight with front post. About as good as I can do with my eyesight these days.


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## T Bredehoft (Aug 9, 2018)

I probably couldn't see the plate at 100 meters. Good Shooting. Nice clean holes, too.


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## dulltool17 (Aug 9, 2018)

Outstanding machining and outstanding results at the range!  What powder are you using, Jay?


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## jbolt (Aug 9, 2018)

dulltool17 said:


> Outstanding machining and outstanding results at the range! What powder are you using, Jay?


Im using IMR 4227. 

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## jbolt (Aug 9, 2018)

T Bredehoft said:


> I probably couldn't see the plate at 100 meters. Good Shooting. Nice clean holes, too.


Every year it gets harder to see. 

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## dulltool17 (Aug 10, 2018)

jbolt said:


> Im using IMR 4227.
> 
> Sent from my SM-G955U using Tapatalk



Probably the optimum for cast, especially in a rifle.  You'll be receiving accolades at matches!


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## jbolt (Aug 10, 2018)

dulltool17 said:


> Probably the optimum for cast, especially in a rifle.  You'll be receiving accolades at matches!


 If I can pick up one or two more targets at a match I'll be happy?


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