How do you FIT a boolit or design it for a lever action with a deep throat?

[MBTcustom]

Thanks everybody for weighing in!-goodsteel

Thanks for the mental gymnastics, it's been very educational.
I always wondered why pistol cartridge leverguns had chambers with such a long leade. Only theory I've come up with has something to do with their black powder heritage. Figured maybe the long leade was to keep powder & lube residue a place to build up a bit and still allow rounds to be chambered. Don't know if that's true or if it will help improve the fit but sometimes the history of an issue helps with the solution.

You know, I'm not really convinced they have a long lead. It's just that they have no step in front of the case mouth like a bottle neck does and instead start their lead in taper at the case mouth diameter. As the trig goes, for every thousandth of an inch you gain in diameter, you gain gain .018 in length of the lead. So it's kind of a trick. Most of the lever guns I have worked on have pretty obtuse angles on their leads, but that's offset by the fact that the throats are starting out at the neck diameter. Not the groove diameter.

[runfiverun]

actually it's closer to a semi-auto handgun/rifle.
if you look closer at the pictures tom provides and focus on just the throat area, you'll see where brads boolit picture coincides with the nose shape and the throat shape.
we are trying to achieve a mechanical throat fit on the run.
it's a similar principle to a bolt gun where we back the fitted boolit [or tune a load by oal with a jacketed bullet] out of the throat slightly and speed up the powders burn rate to gain velocity.
we don't want the initial pressure spike from [and from using a tooo slow powder rate] jamming the boolit into the rifling any longer, we now need a bit slower rise before contact then the spike from engagement.

Tim:
remember the phone conversation we had a bit back about starting things out as straight as possible to begin with?
we can't get to 100% here due to other issues [oal, feeding, whatever] so we have to get as much as we possibly can from every angle.
we go as far as possible before damaging the base of the boolit by sizing it to the barrel.
even doughty's post showed a little less than optimal throat diameter still shot well.
however he still needed a .005 oversized boolit to hold everything straight enough.

now if he could have gotten the centerline alignment without damaging the base upon firing I'd bet his accuracy would have gone up too.
you'd be amazed what a single wrap of .002 cello-tape can do.

[MBTcustom]

But Nolan, you can't put tape on your brass. There's a law against it or something. LOL!
That's a good way to reduce your Boolit size requirement by .003 right off the bat.

[btroj]

Dang it Lamar, did you change your name again?

[runfiverun]

ghost writer,,, I'm a busy man..

anyway I learned a lesson from our government waay back during the shuttle missions.
they spent something like 114 million dollars developing a pen that would write in outer space [that's where GEL pens come from]
the Russians spent 10 cents at the local elementary school and use a pencil.

[btroj]

You are a busy man.....

Nice story about over thinking......

[MBTcustom]

There is no such thing as "over thinking". The brain is like a muscle. It takes work to make it stronger. Which probably explains why so few enjoy using it! (No direction toward present company. It's just a quote I heard somewhere)
In contrast, the above is an example of gross over engineering.

[runfiverun]

over thinking things sometimes gets in the way of seeing things clearly.
what we call the dumbest smart guy syndrome in the patch.

it's why I recommend taking a pound slug of your throat and then outlining it on a piece of paper and just sitting there looking at it for a while before making a second step.
you'll start to see a picture of what you should be looking at in terms of a real functioning boolit before too long.

[btroj]

Overthinking is possible. Don't try to find such an elegant solution that you pass up on many quite workable, very doable, very good designs.

Good enough is good enough. Trying to find perfect can drive a man crazy, and get expensive.

Don't believe a solution can be overthought? Ask Rube Goldberg, he knows a thing or two about it.

[Tom Myers]

over thinking things sometimes gets in the way of seeing things clearly.
what we call the dumbest smart guy syndrome in the patch.

it's why I recommend taking a pound slug of your throat and then outlining it on a piece of paper and just sitting there looking at it for a while before making a second step.
you'll start to see a picture of what you should be looking at in terms of a real functioning boolit before too long.

About 5 years ago I came to the same conclusion. I had already developed the Precision Cast Bullet Design software to the point where a bullet design could be accurately designed and evaluated. I was determining the dimensions of the bullets almost exactly as you suggest - on paper. The designs were fitting and working well but a final design consumed many hours of work with constant re working due to simple math errors and the inability to sketch the chamber accurately to scale.

The next logical step was to develop a Chamber Drawing module that could produce an accurate scale drawing of a specific chamber from a database of dimensions determined from a pound slug or chamber cast. That worked well and cut the time required for a useable design almost in half. But it still required utilizing existing Windows imaging software to overlay and manipulate the placement of the bullet design within the sketched chamber throat-leade area.

Two more modules were needed to really construct repeatable, accurate designs that actually worked. First the database driven Cartridge Case drawing module was developed and then finally the Overlay module.
Now all the units could be accurately dimensioned and those dimensions stored in databases where each individual drawing module could retrieve those dimensions then draw and store on the computer, a scaled, dimensioned sketch of the chamber, cartridge and bullet used fore each design.

The four design modules, Chamber, Cartridge, Bullet and Overlay, made it possible to retrieve and display the drawing of each unit in a composite drawing that allowed accurate movement of both cartridge and bullet within the chamber to achieve the desired design.

Now things were working really well and practical, useable bullet designs could be designed for nearly any chamber and cartridge combination. However trial bullet designs still needed to be determined by pen and paper calculations, with the resulting rejects, until a useable design was achieved.

The last, but probably not the final, step in the on-going project was the Cast Bullet Design~Ultimate module. This unit access each database for critical dimension values and then determines an initial bullet configuration conforming to pre-determined design parameters. Those parameters are partially editable before the values are actually exported to the Bullet Design module for final editing so the number of reject designs has been nearly eliminated.

Throughout the entire process, the ultimate goal has been to allow anyone, with average computer skills, the ability to construct a practical bullet, designed according to known proven parameters, that dimensionally fits a certain chamber. A comprehensive sketch of that design can then be sent to a mold maker with a reasonable certainty that no more designs and molds need to be cut before finding one that actually works.
After many, many hours of writing extensive help manuals and context sensitive help hints, I believe that goal has been reasonably met.

Although the software doesn't appeal to all, it is just another tool to aid in our quest for more functionality and accuracy from our Cast Boolits.

[MBTcustom]

Really ingenious Tom. I love it!
As soon as I can get together enough scratch to take care of the itch, im going to do just that.
This thread is actually a pretty impressive demonstration of the power of your program.
Gotta give you an internet high five!

[runfiverun]

I'm using the older bullet design pro.
it has some frustrating features..
but will draw a reasonable boolit if I use my head about what I really want.
the paper thing really helps me because I'm not reasonably computer literate
so I have to think things through on how a boolit throat relationship is going to actually work.
a static [non moving] mechanical fit is a whole different thing compared to a moving mechanical fit.
leverguns and pistols are almost a total loss when it comes to a static mechanical fit so you have to look for the moving mechanical fit as part of the working compromise.

[MBTcustom]

I'm using the older bullet design pro.
it has some frustrating features..
but will draw a reasonable boolit if I use my head about what I really want.
the paper thing really helps me because I'm not reasonably computer literate
so I have to think things through on how a boolit throat relationship is going to actually work.
a static [non moving] mechanical fit is a whole different thing compared to a moving mechanical fit.
leverguns and pistols are almost a total loss when it comes to a static mechanical fit so you have to look for the moving mechanical fit as part of the working compromise.

See, that's the whole reason for the thread. I mean, if you are talking static mechanical fit, that's where I live!!! I have taken that to levels that most people will never achieve (no brag, just fact, and I'm lucky to have the machinery to make it happen) but what happens when things start moving, exploding, turning, engraving, slumping, and harmonizing? Well, I'm pretty much lost, but I'm trying to catch up.
I'm shooting into a box of sand at cat sneeze levels to try to learn the basics, because here in Arkansas, we don't have nice powdery stuff to shoot into at long range. Here, you're shooting into rock laden mud which means your boolits are either lost, or severely damaged.
I thought about building a crumb rubber trap, but I just don't have time to do it, nor do I have property to shoot on where the patrons don't mind having crumb rubber strewn all over the place, so the only way for me to see a lot of boolits that got shot (albeit at 350 FPS) is the sandbox.
Now, what I have seen has been educational! I see boolits twisting as the lands engage the front of the boolit and the rear catches up. I see improperly fitted noses skidding as they engrave the rifling, I see fins being wiped into lube grooves as the lands ride over them, I see rifling's that are deeper on one side than the other. All kinds of cool stuff, and I theorize that the boolit might be launching into the throat at very similar speed as it does at high velocity. I mean that boolit doesn't just start moving. It takes an inch or two of barrel to get up to speed, so I'm thinking that it might not be that different to the nose of the boolit whether it's being pushed by 2 grains of Bullseye or 45 grains of 4895.
I'm fixin to find out if all that matters on paper at higher velocity. I have managed to find a boolit that fits better.

But this little rifle here really made me think about dynamic fit, because I don't have my perfect chambers to use as a crutch. Very interesting!

[Pb2au]

A camel is a horse designed by a committee. It is my favorite example of over thinking. It is possible to desire so many specific things, you can often overlook the most basic elements that are the key to success.
This is an excellent thread by the way. Absolutely filled with great info. Thanks to the contributors for their time.

[dkf]

Maybe if you could find a good gunsmith they could rebarrel the lever gun for you.

[runfiverun]

wow,,, now I gotta go get a towel...

this is where it gets a bit confusing.
you get to see an actual boolit with your trap but it's not under actual conditions.
your doing a simulation.
I think you can simulate several parts of the sequence through alloy manipulation and pressure matching but you can't quite get 100%.
you can however make some good observations [hopefully notice some trends] and use those to make a logical leap...
you'll be able to see what happens with a fast pressure spike slapping a dead soft boolit forward suddenly and why that's a bad thing for sure.
you'll also be able to see what happens with a normal off the shelf mold that doesn't quit fit the throat right and observe the difference between it and one with the correct mechanical support.

[runfiverun]

ohhh one more thing that will help.
mark the boolit and case and use chamber alignment techniques, then you'll see a bit more of where on the boolit it's getting the damage.
bottom, top, whatever, that will help you with the centerline picture...

[MBTcustom]

wow,,, now I gotta go get a towel...

this is where it gets a bit confusing.
you get to see an actual boolit with your trap but it's not under actual conditions.
your doing a simulation.
I think you can simulate several parts of the sequence through alloy manipulation and pressure matching but you can't quite get 100%.
you can however make some good observations [hopefully notice some trends] and use those to make a logical leap...
you'll be able to see what happens with a fast pressure spike slapping a dead soft boolit forward suddenly and why that's a bad thing for sure.
you'll also be able to see what happens with a normal off the shelf mold that doesn't quit fit the throat right and observe the difference between it and one with the correct mechanical support.

Exactly. That's all I'm trying to do. Just because it's not the same, doesn't mean it has no value. I mean the boolit still has to jump, and it's still got to engrave, and my thought is that if it's entering the rifling crooked at low speed/high pressure, that is not going to improve with a full pressure load. Of course, I realize that I could get something that looks great in the box that doesn't do worth a darn at full pressure, but that doesn't mean it has no value. I'll take something similar that I can measure any day over something that is exact that I can't. I'm trying to see something that can't be seen. I've thought up a bunch of different ideas, but this one is the cheapest, and easiest, so I'm trying it out for a while to see if there is anything I can glean from it. I'm prospecting.

SO far I have learned that something that does bad at full pressure does bad in the box as well and something that does well at full pressure seems to do well in the box also, but I am a long way from proving to myself that the results correlate or to what extent they do or where.
It costs me nothing, and it's possible it might help. So why not observe, measure, and document?
It's a nice thing to do whilst taking a break to smoke a cigar. LOL!

[runfiverun]

yessir.
oh and don't do it down in the basement.
the wife get's mad when you knock the dust off the rafters down there. [especially if she is standing directly overhead drinking a soda]

you could pull up some of 303 guy's posts and see what results he got with his drum/rag trap and some of the things peter got to work in a couple of his rifles.
we pm'd forever back and forth about a couple of things that worked, and some that never should have worked but did just because of fit.
the waxy dip lube might be of interest to some too, it is the ultimate time saver because no sizing is done.
and the lubing is done after the round is loaded.
it goes along here in parallel lines pretty well.

[MBTcustom]

yessir.
oh and don't do it down in the basement.
the wife get's mad when you knock the dust off the rafters down there. [especially if she is standing directly overhead drinking a soda]

you could pull up some of 303 guy's posts and see what results he got with his drum/rag trap and some of the things peter got to work in a couple of his rifles.
we pm'd forever back and forth about a couple of things that worked, and some that never should have worked but did just because of fit.
the waxy dip lube might be of interest to some too, it is the ultimate time saver because no sizing is done.
and the lubing is done after the round is loaded.
it goes along here in parallel lines pretty well.

Well, I must confess, I have swapped PM's with Peter a long time ago as well and asked a lot of questions about his test tube.
I don't intend to take it as far as he did, but I do think there is something to be learned from it. I'm just using it to help me get my head around what happens to a boolit at launch.
I keep racking my brain trying to figure out how to catch a soft cast lead boolit fired at 2400fps out of an 8 twist rifle, and do it so that I can see the part of the boolit that engraved the rifling.
I have studied on some difficult problems in my time, but that seems to be about like trying to catch a ray of sunlight. Wish I had an answer.
Anyway, this is about as close as I am liable to get and even this is almost enough to wipe out the engraved nose of the boolit.