Ordering Dies, Bullet Design

[beezaur]

Hi Guys,

I am about to embark on the bullet swaging journey.  I will do both rifle and pistol, but my primary intent is making my own long-range rifle bullets.

I spoke with both Corbin and RCE.  Apparently which ever way I go I need to more or less be familiar with bullet design: required twist rate, jacket thickness/core alloy issues, ojive specification, etc.

I know from my searching here and elsewhere that long range bullets can be troublesome to make.  How do you decide what to order?  Are there any design tools available to help the process?

I will be swaging for probably 6mm and 7mm first, then .30 cal within a year.

Scott

[talon]

beezaur, Bullet Swaging, like most other crafts, is a much larger, more complex subject than it first appears. Are you going into the field as a hobbyist or a nitch commercial manufacturer/seller? Have you read Corbin's " Rediscover Swaging", or his Hand Book #8 yet? That is where to get started. And, yes, Corbin does have several software programs that works out bullet flight-drag problems and design. As to how much you need to know about making a long range bullet: I almost guarentee you can make a fairly good one, or two or a bunch within 30 minutes after you get set up with your new tools and supplies. Then, you'll spend another 50 or so years learning the why's and how's to make even better ones.  

[beezaur]

Thanks, talon.

This is just for my own use.

I have the Corbin book on its way, and have perused a lot of their material on their web.  Also I have the books "Modern Exterior Ballistics" by McCoy, and "Rifle Accuracy Facts" by an author whose name escapes me.  Yes, you are right: this is a very deep and complex subject.

I have read in those books and on various forums about the woes of fast-spun, low drag bullets.  It seems sometimes they can be prone to blowup, which apparently is the result (at least in some cases) of being spun so fast the core squirts out the side.  "Facts" talks about core stripping as well, where the jacket is spun up too fast, causing the core to strip and induce bad effects when the core and jacket equalize after the bullet leaves the barrel.  Plus you have a host of aerodynamic problems alluded to on Corbin's site and explaiend in McCoy.

The problem is putting thise ideas to practical use.  It is one thing to say I want a 14-caliber secant ojive, rebated boattail of such-and-such dimensions.  It is another thing entirely to spend $700 on a set of dies for high performance bullets that might or might not have problems with blowup, core stripping, etc.

It seems there are three stages to understanding.  First you are happily oblivious.  Next you know enough to be scared.  Finally you get your bearings and can navigate the problem reasonably well.  Right now I pretty much just know enough to be scared of wasting my money.

I'll certainly give the Corbin software a good look.

Scott

[talon]

1st, read at least one of the books I mentioned. Then reread it before doing anything else. You will note that 99.99% of the text concerns itself with the physical act of bullet swaging, not the thought that goes into selecting exactly the right bullet for you, and the testing thereof. That is because, otherwise, the 'book' would be a library.  Richard emailed me a bunch of paragraphs only last week concerning the types of jacket material available and their characteristics. Then there's different lead alloys. Each sub-set of this art/science is a whole subject in itself. Take the spinning of a jacketed bullet that throws lead 1/2 a nanosecond before it vaporizes in flight: just how many factors do you think are involved in this situation? Myself, I have absolutely no idea. I'm sure ogive, lead alloy type, type and thickness of jacket, amount of exposed lead tip, debth of barrel lands, velocity, air temp , density, and wind have a lot to play, but certainly there's more.... , but it's all I can do just to try to control how I make a bullet that works most of the time. To be a successful problem solver, you attack it one small part at a time. Now, the cost factor: Swaging is not inexpensive to get started in, and even the bullets you make 'cost' from 2 to 5 times as much to make as cast bullets do. I've found, thou, that swaging presses and dies hold their value very well, and the bullets they make can be much better performers than cast ones. ( If all you want to do is plink at tin cans at 25 yards, cast bullets are a much better deal). More to the point: It will cost you about $1000 to make that first 6mm Ultra Low Drag bullet you want. There's the press, and at least a 4 die set (CSW, RBT-1 and -2, and PF), jackets and lead cores and lub, and some small bench tools. Then there's a 8-14 month wait for the swage tools and exact length and thickness of jackets to be made. It's this waiting more than the dollar cost that's THE problem in bullet swaging.
 

[beezaur]

I really don't see the $1000 startup as a big deal.  It is very easy to spend a whole lot more than that on an accurate rifle and scope.

With the blowups I pretty much feel the root cause is weak lead.  I calculated the acceleration field a while ago, and it was hideous.  The centripetal acceleration in the core just inside the jacket was in the hundreds of thousands of gs for most bullets, if emory serves.  Weak (more elastic) lead puts more force on the jacket than stiff lead, so the jacket blows out.  There is a retired ballistics researcher with a web page somewhere with finite element analysis on the topic.  A lot of these low drag bullets are on the ragged edge of failure from centripetal forces.  Here is a plot I did of a few reports of witnessed bullet blowups with .22 cal, 6mm and 6.5mm bullets:



The dots are blowups.  The colored regions are evenly spaced centripetal acceleration regions -- lower right is mildest, upper left is most severe.  You can see that centripetal acceleration, and thus force, increases very rapidly with velcity and especially twist.  A typical .308 Win might be 2800 fps/1:10" twist, for comparison.

Basically the force goes up linearly with velocity and with the square of twist.  So, with VLD-type bullets you are running a fine line between having enough stabilization and blowing a jacket.  My 31" barreled .280 Ackley Improved that is getting a stock right now might not have been such a good idea.  It was supposed to be a 1500-yard rifle.  Time will tell if I can push 7mm VLDs that hard.

The .280 AI is one rifle that I would swage for right away.  Another rifle I am building will be a .308 Win, which will be much less picky about its food, so to speak.  With both lower velocities and twist rate, the bullets will be subjected to much lower forces.  Swaging something equivalent to a Sierra 175-gr MatchKing should not be a very exotic job.

You mention Richard, so I assume you use RCE equipment or maybe an adapter for Corbin?  How do you like it?

Scott

P.S.  I should clarify that I believe VLDs to be in danger of failure only when they are pushed hard.  They were originally developed for medium power cartridges, and work quite reliably in that application.

[talon]

Beezaur, I may have some bad news for you: You are going to have to use soft lead in most of your bullet swaging unless you let the diemaker know you want the dies and press built to work with hard lead(BnH greater that 9)((wheelweight metal is +/- BnH12)) Such tooling will be at a higher cost to make, and may not be recommended for anything less than powered presses. After you read the Corbin swaging books, give one(both) of them  an email or call and discuss your thoughts and requirements. At this point I believe the Walnut Hill dies are stronger than Corbin's 'S' series, but I don't know if they are strong enough for your purpose. I do not have any. From your graph, it appears that 'blowups' occur in that velocity and twist rate range quite a bit beyound normal speeds and available barels. Are you involved in testing frontiers? If so, you being able to swage 'speciality' bullets would be a great addition to your testing efforts.

[beezaur]

I am aware of the limitation to soft lead, and it should not be a problem.  It is a factor in deciding what to specify in an order for a set of dies, however.

The blowups came from match shooters firsthand, and were witnessed either by the shooter or the spotter (usually the spotter).  It had to be a witnessed puff at around 100 yards, not a "lost" bullet presumed to be a blowup, nor a puff at long range (which is more likely an atmospheric effect).  These are loads that are "normal" long range loads, high-performance, but otherwise nothing special; VLDs shot out of .223, .243 Win, 6.5-284, things like that.  There is a thread on long-range.com where I got the information.  I excluded many more reports because both twist and velocity were not reported.  But if you make the usual assumptions, the excluded blowups would fall with the others.

These bullets don't blow every time.  Sometimes you get reports of someone having a high percentage of blowups, say 75%, with a given load on a given day, but usually you just have a single bullet blow every so often, maybe 1% on average.  A lot of shooters would never detect that.

Again, these are regular handloads shot at matches with the same barrels and bullets everyone else is using: Berger, Sierra, Hornady, etc.

Eric from Berger made an interesting post on the thread about the work Berger was doing to prevent blowups.  His contention was that the lead was the culprit, much as I believe.  Obviously I don't know what they are doing, nor is that information available.  It could well be that Berger, with their more substantial equipment, can do things like make harder cores that I cannot do with equipment I can afford.

I have no doubt that I can swage my own VLDs (ULDs).  However they might only be suitable for milder cartridges, say, 6.5x47 but not full-power 6.5-284.

As for testing, I do some of that.  I do things like hook accelerometers to my rifles and analyze the motion during firing.  I do some finite elements programming and am working on some computational fluid dynamics (CFD) stuff.  It is a hobby.  The CFD is for stream research, but hopefully it can be used to make an external ballistics program someday.

Scott

[Adam/Orion]

Hi everyone,

Some input from a new boy from the United Kingdom. Also a professional jacket and bullet maker. Reading through the postings I must say the following. There is no substitute for knowledge and experience in bullet  making per se. My advice to Beezaur partaking in this discussion would be to forget what one knows or one thinks one knows about ballistics and the like and go to any of the following  persons  Richard Corbin, David Corbin  and, possibly, Dr Larry Blackmon  in that order and in all humility and simply tell them what he wants to achieve and also what he wants to avoid. In my experience one normally gets something that works just so. There are other diemakers who some might argue  make better dies. The Benchrest fraternity, in particular nurture this belief. Even if that were true, and in my personal experience of 20 years in bullet making it is not, that is indeed what they are, in fact, die makers. The aforementioned persons are not just machinists, they have accumulated a vast amount of knowledge about what works and about what surprisingly but regrettably does not work in bullet making/design through research and through offering dies pretty much in all rifle and pistol calibres. The discussion so far highlighted the fact that a lot of significance has been given to the use of pure  lead alloys, loads,  barrel twist etc but lamentably very little to jacket features and jacket manufacture and construction. A point has been raised about Berger's use of hard lead. It may well be the case that Berger's found it necessary to use hard lead, perhaps only in some bullet designs,  but this is directly linked to the use of their jacket/s in the bullet manufacture. In particular related to how their jackets are made. Other jackets of different manufacture and with different features do not need hard lead to perform. Incidentally how hard is hard? How can one guarantee to obtain the same amount of hardness in a  billet of lead alloy to draw wire from, batch after batch and at what cost? Bearing in mind also that the action of drawing the  wire also softens the lead considerably!! What price accuracy and consistant obturation?

Food for thought
Adam/Orion