A Beginner's attempt at Boolit Design - Critique Welcomed!

[DrCaveman]

I am probably in over my head, but I like CAD so I went ahead and came up with a few boolit designs for 38/357 guns. I would greatly appreciate any comments from people who have submitted their own drawings for custom molds, and who may have had to change certain aspects based on the reality of CNC capabilities/proper mold fill-out/boolit release from mold, etc.

I am pretty ignorant of proper lube groove depths or widths, but I think this is an area of significant flexibility... but any insight is very welcome.

Or, if you just think the design is a bad idea, for whatever reason, let me know!



This has a pretty standard SWC front, but I gave it some extra length to bump up the weight and increase the length of full-diameter driving bands. I am attempting to combine Tumble lube grooves with more standard lube grooves. My thinking is that low pressure loads just get tumbled, while magnum loads would get pan treatment in addition to being tumbled.

The odd shape of the two larger lube grooves was also intentional, my thinking that the liquifying of the lube would create small eddy's near the bottom of the groove, keeping the lube in the groove a little longer. Maybe pure hogwash, but it kinda makes sense.





This one is intended as a big-boy hunting/SD round, shot around 1000-1200 fps with pretty stout loads. I drew this one first, and I have a feeling that all the square corners may pose problems in fabrication as well as mold operation. All that can change easily, but for now I just wanted to see what everyone thought of the general shape and groove placement.

As with the previous design, I am attempting to combine large lube grooves with small ones, since I would like to find a boolit capable of shooting within a variety of temperatures at a variety of pressures. Again, I figure that the bottom groove will be filled with some heavy duty pan lube, while the top grooves will be more like Tumble lubed. This boolit has a full 50% of its length at full diameter.

Thoughts? Thanks in advance. I am still very new to all of this, and my skin is thick. Dont be afraid to beat me up, or knock some sense into me.

[excess650]

Radiused bottoms or angled sides in the grooves will make for a stronger boolit. Too, it will be easier to make tooling for radiused corners, angled grooves, etc and boolits will drop more easily from the molds if the corners aren't as sharp.

If these are to be shot from a revolver, the distance from the crimp groove forward plus case length needs to be shorter than the cylinder. If for a lever action, the OAL will need to be less than the maximum the lifter will allow for.

Take a look at Ranch Dog's designs or NOE's version of the RDs and NOE's .360 WFNs.

[geargnasher]

+1 on radius and draft angle. The boolits won't drop from the mould unless everything, including the larte meplat, is angled. Note most boolit designs have a minimum angle on all things like the top of the crimp groove and even the front shoulder on the boolit.

Gear

[DrCaveman]

Alright, these are the types of comments I was looking for!

A couple things:

I determined the distance from crimp groove forward by measuring loaded rounds that work fine in my gp100. The large front driving band on the larger boolit may be an obstruction, I need to test a little more to know for sure. In short, I was working with .32" as my max protrusion from a 357 case.

Gear, what is meant by 'minimum angle'? I can easily draw the boolit with an angle at every location, but when do I specify a particular degree, and what should that degree be? Presumably, different at almost every location, but is there a rule of thumb for 'straight' edges?

For instance, I worked off of Lee's drawings of their tumble lube groove to determine the dimensions of the lube grooves on the 187 gr swc boolit. This was 26 degrees from straight, 0.04" groove width with 0.01" band between.

For supposed 90 degree corners, what is typical back-off? 2 degrees? And will the custom mold makers adhere to this, or just do what is easier? Or, to my chagrin, do exactly what I request?

[MT Gianni]

I get no leading with the 358429 or the 358156. I don't think that you need as much lube groove as you have shown in the top boolit.

[runfiverun]

it's a draft angle that will allow the boolit to come from the mold.
you have to use it for everything from fiberglass to lead.

you really don't need a lube groove any deeper than the height of the lands.
the riffle effect of the lube grooves is not applicable.
it works fine in water but lube is not alway's liquid [it has different stages],and you don't want it rolling around in there when it is.
this will cause cavitation and heat, you could also compress the air [created by the cavitation] or cause a dieseling condition.
it needs to flow along the cuts made from the rifling sealing any passages that the gas could follow,and lay down a friction barrier to prevent galling.
think about lube as ski wax.

[DrCaveman]

I get no leading with the 358429 or the 358156. I don't think that you need as much lube groove as you have shown in the top boolit.

Ok, fair enough, as I haven't seen any leading from my TL boolits anyway. Are you saying that I could just ditch one of the large lube grooves entirely, and maybe have a full diameter driving band instead?

I may be putting words in your mouth, but this seems to be where it's headed. Maybe I knock a few hundredths off the length to keep things around the 180-185 gr range, while getting rid of one large lube groove. Getting closer to Keith design.

[DrCaveman]

it's a draft angle that will allow the boolit to come from the mold.
you have to use it for everything from fiberglass to lead.

you really don't need a lube groove any deeper than the height of the lands.
the riffle effect of the lube grooves is not applicable.
it works fine in water but lube is not alway's liquid [it has different stages],and you don't want it rolling around in there when it is.
this will cause cavitation and heat, you could also compress the air [created by the cavitation] or cause a dieseling condition.
it needs to flow along the cuts made from the rifling sealing any passages that the gas could follow,and lay down a friction barrier to prevent galling.
think about lube as ski wax.

You said a lot here, I think. Not sure what you mean by cavitation, but I presume it has to do with creating pockets of air. It sounds like you see these as a bad thing, I will take your word on that.

Lube groove no deeper than lands... What boolit out there adheres to this standard? While I can understand what you are saying, I have owned no boolits or moulds which satisfied this measure. It kinda sounds like you are saying: the shallower the better!

Since I like my Lee TL boolits so much, I will not argue, but this seems to be in opposition to mainstream mould design. Am I missing something?

In any case I will modify my dwgs and put out some new ones tomorrow morning based on the critique.

Thanks for comments thus far.

[subsonic]

I am no expert, but here's how I see it.

You can TL any boolit, so your TL section is superfluous and gives up bearing surface while weakening the boolit for no good reason and making the mold more complex.

My personal feeling is that the lead used for driving bands is put to better use at the front of the boolit where it grabs rifling first and tries to strip, rather than at the rear where it is mostly just functioning as a piston ring. This will also affect bore friction, which relates to engraving pressure and speed.

I would suggest making lube grooves DEEPER than the rifling depth by at least .002" per side. You want to leave some room for displaced lead while not adding bore friction for no gain. I would try for around .8gr of lube on these boolits.

A lot of the guys that get great revolver accuracy tend toward several (3-4) narrow lube grooves instead of one big Keith type groove. But some report great accuracy with the Keith type groove too.

Your drawing states these boolits will be 187 and 194gr. Be aware that the GP100 has a 1:18.75" twist, which is fairly slow. You may have an issue here - do your homework on this by seeing what others are experiencing with similar weight boolits in GPs, or try an existing boolit at 100yds in this weight range. You may only get longer range (past 10yds) accuracy at top level loads. Be aware that the SWC style boolit is longer for weight than an ogival design like a WFN, WLN, or even a TC. This length may add to the twist rate required. If you plan to shoot living things with this boolit , you want to make sure it is VERY stable in air, because stability in meat is even tougher to acheive.

Others may say I'm full of BS. They are welcome to critique my statements - but these are things I would definitley consider before cutting this mould.

While re-invinting the wheel may be a fun pastime, there are reasons why existing wheels are round. Don't overlook the theory of KISS.

[nfg]

Mountain Molds has a very nice bullet design program that also has links to specific information on almost all aspects of cast lead bullet design and a good place to look for information is www.lasc.us with included links to other sources.

I'm new to casting also, but have been designing bullets and turning them from brass and wildcats for a LONG time...cast bullets have some particular areas of concern that are outside "normal" bullet design so spend some time working out those particular "problems"...all that data is well covered in the above two links.

Nothing wrong with reinventing the wheel considering the long development from wooden to modern rubber tires.

[DrCaveman]

Man, the more I tweak my drawings, the closer the boolits look to Keith designs. I'm beginning to feel that this is an exercise in futility. I was hoping to come up with something groundbreaking, or at least inspire someone else into a new innovation.

One main goal was the ability to fully utilize two types of lube, to provide a wider range of operating pressures. I guess those 'tumble lube grooves' are an uneccesary addition, since an alox-type lube will coat all surfaces of the boolit. And if I just try to make little grooves the entire length of the seated portion of the boolit, 2-3 thousandths deeper than the rifling depth, I am basically looking at a standard Lee TL design.

Am I wrong, or does liquid alox work better with shallow grooves? And conversely, wax/hard lubes work better with a bit deeper grooves? If this is correct, then why don't more mould designs use two sizes of lube groove?

[subsonic]

I think the whole reason the Lee uses small, rounded lube grooves is because they are easier to machine and also fill out easier when casting. Your reject rate will be lower on molds and castings.

But if you get the temps right and have some tin in your alloy, the castability factor is a non-issue.

There is a reason why almost everybody likes Keith and/or LBT style boolits.

If you want to innovate, I think the direction things are heading for the innovators does not include lead.

[turbo1889]

DrCaveman, I am a man who has already traveled at least part of the road you are considering going down. I will attempt to give you some pointers as I see them based on my experience thus far.

I have designed and am using a total of three hybrid boolit designs that use both Lee type tumble lube boolits and conventional lube grooves combined together on the same boolit design. Here are some pictures which are clickable links to the boolits in question (clicking on the picture will take you to the web site of the mold cutter who made the boolit mold for me showing a CAD view of the boolit with dimensions). They are in order of development and they all have flaws and things I learned along the way:

Hybrid Design #1 ~ 35-cal maximum weight thumper boolit for 38-spl./357-mag./357-max.




Hybrid Design #2 ~ “fat” 30-cal rifle boolit for 303-Brit./7.62x54R/7.7-Jap/7.62x39




Hybrid Design #3 ~ heavy weight 30-cal rifle boolit for 30-06






Okay, now on design #1 I learned the following:
----- I had more “conventional” lube capacity then I needed and on most loads I had better accuracy if I only filled one conventional lube groove instead of both and there was enough lube and I didn’t get any leading but for some of the 357-max carbine loads I needed to fill both lube grooves because one was not enough to prevent leading but if I filled both although the leading at the end of the barrel went away the groups opened up a little because the boolit was “too slippery”.
----- The plain base worked fine for the 38-spl and most of the 357-mag loads but for some of the 357-mag loads and most of the 357-max loads a gas check would have helped as was confirmed by installing some thin pop can metal plain base gas checks that swag over the base of a plain base boolit in the sizing die.
----- For load data availability 210 grains was just a little too heavy. Not much load data for boolit weights over 200 grains and I would have had more load data to work from if the boolit had been just a little bit lighter since there are loads for 190,195, and 200 grain boolits that this boolit was just a little bit heavier then so reducing its weight by 10-20 grains would have been advisable for load data reasons.
----- The third drive band up from the bottom, the one directly above the upper conventional lube groove is too thin, narrow, and fragile and is crushed too easily when crimping in the bottom Lee type tumble lube groove directly above it at the base of the nose.

If I were to do it over again this is how I would change the hybrid boolit design #1 according to what I learned (original on right, improved to left):


----- Capacity of the conventional lube grooves is reduced.
----- Base band is a gas check shank.
----- Length and thus weight of boolit is slightly reduced.
----- Thickness of third drive band up from the base is increased.




On design #2 I learned the following:
----- The problem with this design was the shape of the nose. I had originally specified the nose to be a flat tipped truncated cone shape with sharp crisp edges which although very accurate and effective on game was absolutely terrible for feeding. Not a single magazine gun I owned (disregarding the single shot break action 7.62x39) in the calibers in question would feed the boolit with the original nose shape from the magazine into the chamber without jamming up when that sharp end on the tip of the nose grabbing on any and every little edge in the guns action. They had to be fed into the guns chambers one at a time by hand. Other then that it worked great. The ultimate solution I arrived at to fix the mold I already had in my possession was to bore out the nose section on one of its two cavities with a 3/16” ball end mill cutter so that one cavity produced a round nose boolit profile. I also informed the custom mold cutter of the problem and he modified the design in his catalog (as you might have noticed when you clicked on the picture) so that the tip of the nose has a rounded edge instead of a sharp edge like it originally had.



The resulting round nosed boolit produced by one of the two cavities on the mold now feeds no problem through all my guns including semi-auto SKS and AK-47 guns when loaded in the 7.62x39 cartridge. I got lucky though in that the angle on the nose along with the size of the flat on the nose allowed a common 3/16” size ball end nose mill cutter to match up so well to successfully convert the mold. If I were to do it again I would use a nose shape like found on the AM# 31-087T (Clickable Link) design which feeds very well and still maintains a 0.18” flat meplat on the nose for effective hydro-shock wave terminal ballistics and does not require a slow painstaking modification to be made to the mold after the fact.




On design #3 I learned the following:
----- The heaviest possible, longest possible boolit that will fit, feed, and be stabilized by the rifling of one’s gun is not necessarily the best choice for a cast boolit for big game hunting with cast boolits even though initial impressions may point that direction. The boolit is stable and accurate in flight when pushed to the top end of its velocity capabilities out to about 200-yards range. If shots at greater range are attempted and/or the velocity is reduced beyond a top end performance (for cast) load is used the groups open up. When the boolit strikes a living flesh and bone target it tumbles inside the chest cavity of the animal hit and does not hold true and punch through nose first all the way through. This has the desired lethal effect on both coyotes and deer but I can’t trust the boolit for heavier game like elk and although they don’t run far before lying down and dying I can’t help but wonder if a boolit that held stability better and punched through nose first in meat would make them “bite the dust” in their tracks right there where they were hit. A slightly shorter and lighter weight boolit or a gun with a faster twist rate in the barrel might produce better results.
----- There is a better and simpler way to do the DD rings at the base of the boolit tip at the end of the bore riding nose section (a triple set of them on this boolit). The small raised ring that engraves in the rifling is what is desired, forming a groove of smaller diameter then the main bore riding section in-between them is an unnecessary complication that serves no purpose. Just a simple raise ring (or two or three) is all that is needed like is used on the AM# 31-200N (Clickable Link) design.

[turbo1889]

Now, as to the specific theory or idea behind even using a hybrid design.

It is my personal belief that fit is one of the most important things for a cast lead boolit (and to a lesser extent a jacketed bullet as well) to obtain quality accuracy results. Specifically not only does the main body of the boolit inside the case neck need to be of sufficient diameter but in addition the part of the boolit that extends out beyond the mouth of the cartridge case should fit the throat of the gun and if applicable the lead into the guns rifling “like a hand in a tight fitting latex glove”.

That kind of perfect incredibly tight “hand in glove”, “zero slack”, “kissing gun metal”, “lightly engraving in the rifling” kind of fit is difficult to obtain with a purely conventional boolit design unless one makes a chamber cast or swaged throat impression of the gun in question and then cuts the boolit mold to fit that gun and that gun specifically and only with that kind of perfect fit between the boolit and the guns throat and lead into the rifling so that the boolit gets the best start possible into the guns barrel when the hammer falls and the powder is ignited.

Enter the Lee tumble lube groove profile. One of the biggest complaints about those little micro bands and grooves is that they are too fragile and squeeze down too easily. On some of the Lee boolits (a good example being their TL boolit design for the 9mm) just seating the boolit in the mouth of the case with the neck tension of the brass can squeeze down the boolits diameter a couple thousands of an inch which is enough to make a boolit which is the right size now be undersize and result in both leading and accuracy problems.

The idea is to turn this disadvantage into and advantage. What you do is make the part of the boolit that fits down inside the case neck with conventional full size drive bands and lube grooves that will hold their sized diameter and not get messed up and squeezed down by the neck tension or anything like that. But on the exposed nose of the boolit that is outside the case and fits in the guns throat you use the fragile little Lee micro sized tumble lube grooves and little micro bands and you make them oversize by a few thousands of an inch. Then when a cartridge that is loaded with such a boolit is chambered in the gun all those fragile little Lee tumble lube bands that are a few thousands of an inch oversize all squeeze down to fit the throat of the gun. Thus the simple act of chambering the round in the gun forms the boolits nose to exactly fit the guns throat and even lightly engrave in the rifling depending on the gun and the boolit design which may also use the tumble lube bands like the DD rifling engraving bands that Walt came up with many years before Lee even started making molds much less introduced the micro groove and band tumble lube profile. Because the drive bands are so much thinner all it takes is a minimal amount of force to chamber the round with those little bands on the nose squeezing down to fit the throat exactly and/or engraving in the rifling.

On a bolt action rifle you don’t even notice it unless you are really trying to use a pinky light touch on the bolt and feel for it. The semi-auto actions of the SKS and AK-47 slam shut and lock into battery without even so much as a hiccup and loading a revolver cylinder just takes firm thumb pressure to press each cartridge into the chamber the last 3/8” of an inch or so as the little nose bands squeeze down a couple thousands of an inch to tightly fit the throats of the chambers.






Now as far as tumble lube boolits that use only the tumble lube profile, tumble lube is a surface coat lube. It works just as well on a boolit that has completely flat sides with no lube grooves at all as it does on a boolit with tumble lube micro grooves and bands as far as lubrication is concerned. The little grooves are not there so much as to hold lube as they are there as “relief grooves” to give the lead that is displaced by the rifling somewhere to go. They are just like the little grooves in the sides of the Barnes copper solid rifle boolits and some other brands of monolithic solids that are lathe turned from brass or bronze rod stock. They do also grab a little bit of extra tumble lube with a wicking like effect but not much. And yes they do fill out well and are easy to cast with.

My main suggestion if you want to design a tumble lube only boolit that is to be cut for you by a custom mold maker such as Tom @ Accurate Molds is to simply modify the Lee tumble lube profile with slightly wider bands in-between the little grooves. Simply doubling the width of those little micro grooves from 0.01” wide as in the original Lee tumble lube profile up to 0.02” wide bands in-between the grooves makes a world of difference to make it far less likely the little bands will get squeezed down in diameter by the neck tension when you load them into the case mouth. There are many examples of tumble lube type boolits in the Accurate Molds catalog that use a groove profile that is nearly identical to the Lee profile but have been improved by having the little bands being made a little bit wider and thus not as easily squeezed down and hold their size better. A good example is AM# 36-140W (Clickable Link) and is only one of many that use this simple improvement of making the little bands a little bit wider on the tumble lube profile.

If you want the little bands to squeeze down easily as in using them on the nose of a hybrid boolit as I have explained then leave them as they are at a thin little band of 0.01” as used by Lee but if you are using them on the main body of the boolit inside the case neck and you need them to hold their diameter and not get squeezed down easily then double their thickness up to 0.02” you can even go a little thicker then that if you want but doubling them has worked great for me for when I want to stiffen them up.

[JIMinPHX]

+1 on radius and draft angle. The boolits won't drop from the mould unless everything, including the larte meplat, is angled. Note most boolit designs have a minimum angle on all things like the top of the crimp groove and even the front shoulder on the boolit.

Gear

Make that +2.

A lot of people like square bottom lube grooves because they like the extra lube volume that the corners provide. My experience has shown that most boolits, especially pistol boolits, are over lubed & a radius in the corners makes the boolits drop much more easily from the mold.

[geargnasher]

To answer the "minimum angle" question, at least 15 degrees from perpendicular. Radiused lube grooves are the way to go IMO regardless of what Elmer thought, and as has been mentioned most lube grooves are way too deep. I have a variety of pistol moulds (some I designed, some I didn't) that have lube grooves only .010-012" deep and that's plenty. I've also found that, by and large, two narrow, shallow grooves are better than one, deep groove.

Gear

[JIMinPHX]

most lube grooves are way too deep.

A good example in support of this statement is the little round nose boolit that you get out of a Lee mold for a 9x18 makarov. The lube groove on that thing is about 1/4 of the size that I see on most other 9mm or .38 cal boolits, but they shoot great for me & never lead my bore.

I suspect that as the bearing surface of a boolit gets longer, then the multiple lube groove locations become more important. This is just conjecture on my part though.

[turbo1889]

Black powder loads is where you actually need deep square like lube grooves that hold a whole lot of lube.

[nfg]

I think the only way to get from the bed to the coffee pot is one step at a time...unless you are just married and your wife isn't working...no diss or flame intended.

My point being...it takes a whole lot of heads doing a whole lot of thinking and a whole lot of testing to come up with what we think is de Rigueur today but will be "Duh" tomorrow.

I also think that if whatever you're doing has a commercial basis and most shooters being very conservative, hard headed, prone to paroxysms' and fits over very small "truisms", if you want to "sell, sell, sell"...whatever bullet you DO make needs to be very close to what is considered "the right stuff"...with just a few innovations for the "snowjob" effect.

All the diehard testers of the "lead and dead" crowd are learning the real story and TEACHING the rest of us what that story it's all about.

Everytime a newby or and oldie asks this question a whole 'nuther world opens up for someone with a really "new" idea and there is a chance of a new "truism" being born.

Since I started definitively "learning about lead" I bought a 45-70 NEF BC and rechambered it to 45-120 and a 50-90 Sharps just to "plink" at long range with big, long, heavy, cast lead bullets...I've done everything else that has happened in this sport over the past 50 years and was getting totally bored. This "lead thing" has got my blood boiling again.

I think this "new to me game" is totally awesome and GREAT and lots of new stuff will be learned in the comming years and maybe new types of lubs developed that require even fewer and smaller lub grooves.

There is NO such thing as "Static"...everything moves...either forward to new things or backward as it gets left in the dust.

I have a problem with the first bullet I designed for my 625 HB, like Turbo did with his illustrated bullet, but mine was a "too long a nose" and too little meplat". As soon as my "CasterMan" finishes this run of bullets I will take the mold home and re-configurel the nose cavity with a 135°, 15/32 drill bit to just beyond the flat nose, then use a 5/8" mill to enlarge the cavity a bit more. This will give me a slightly pointed, 75% Meplat and more lead in the nose hopefully to correct the bullets going sideways into the target at 15 yds. I will draw it up in TurboCad so I can work out the actual added area so I can calculate the amount of added lead weight.

It will DEFINITELY look WRONG as far as conventional wisdom goes, but if it works...it works...if not the money was well spent...knowledge always has a price. Hahahahahahahahah

[turbo1889]

. . . I will take the mold home and re-configurel the nose cavity with a 135°, 15/32 drill bit to just beyond the flat nose, then use a 5/8" mill to enlarge the cavity a bit more. . . .

If you don't have your own machine tools I can tell you from experience that the hardest part of doing this kind of modification is keeping the cutting tool centered and being careful not to cut too deep and take out too much material by accident. Here is a link to the thread that catalog my experience with modifing the tip of my AM# 31-180B to a round nose profile with a 3/16 ball end mill cutter. Might be something in there that might help you with your modification project:

http://castboolits.gunloads.com/showthread.php?t=100420





The OP might also want to take a look over at Cast Bullet Engineering’s catalog. They have a few bore riding rifle boolit designs with micro grooves on the bore riding part like my AM#31-180B and AM#31-216T designs have on them on pages 11,13, & 14 of their catalog including their design numbers 285-145GC, 309-150GC, 309-168GC, 309-180GC, 309-225GC, 313-174GC, & 314-190GC. Basically a range of boolits to fit all the 30-cal and “fat” 30-cal rifle cartridges with one for the 7mm cartridges as well. Here is a link to the CBE catalog pages in question that include the designs in question:

http://www.castbulletengineering.com/page0051.html