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Post by rangeball on Apr 14, 2011 14:23:21 GMT -5
Understatement of the year I sped read it the first time, will slow way down to grasp what you are saying, but I think I'm with you. Thanks
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Post by rangeball on Apr 18, 2011 13:31:17 GMT -5
Edge, pretty sure I understand your last post and the affect on bc by lowering/increasing weight with the same profile, but am now wondering what the affect is on predicted twist rate for stabilization? Say one removes 30gr of nose weight and replaces it in the same profile with a plastic tip, only adding a bit of weight but subsequently lowering BC as explained. Will the expected twist rate also lower (in this case increase)? As an outcome of lowered weight, bc or both? Thanks
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Post by edge on Apr 18, 2011 13:58:34 GMT -5
I think that you will find that plastic tipped or large void hollow point bullets require less twist then a lead tipped bullet.
If you look at a Berger VLD bullet cut open you will see that the lead is a long way from the open tip. This lets you use a slower twist then would be needed had it been full of lead, but weighed the same.
edge.
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Post by rangeball on Apr 18, 2011 14:55:47 GMT -5
Thanks. How I'd love to hear your thoughts on bullet construction as it relates to terminal performance on game, specifically whitetail. I know we need mass to give us penetration, and harder materials that hold together without fragmentation (hide the goat!), but I'm curious about expansions, shock wave, etc. I believe hollow point bullets expand to create a larger frontal surface (meplat) to effectively transfer energy, but what if the bullet doesn't expand like in the case of a hard cast lbt bullet? How do you think a solid .40 meplat between 1000-2800fps will perform terminally on game? Some good links on meplat and terminal performance- www.dixieslugs.com/images/Force_Factor.pdfwww.dixieslugs.com/images/357_and_hard_cast_bullets.pdf
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Post by edge on Apr 18, 2011 19:08:32 GMT -5
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Post by rossman40 on Apr 18, 2011 23:29:51 GMT -5
When dealing with bullets it is a balancing act, you can go with a big meplat or huge hollow point for the shock-and-awe slamming effect shooting minute-of-deer. And you'll get it at 100, 150 maybe even 200 but then beyond that your down range exterior ballistics goes sour fast. A higher BC also means the bullet is less effected by atmospheric conditions, air density and cross winds plus retaining speed means flatter shooting. So if your bad at reading the wind or ranging the error is less. Probly the high technology lead core bullets has to go to the German company RWS, www.rws-munition.de/en/products/centerfire-rifle-cartridges/bullets.htmlBut some of these are expensive bullets to make and maybe a bit overkill. Probly one thing that they have added to more bullets is the sharp edge at the shoulder. This acts as a hide or hair cutter as the bullet is going in. Going thru the hide going in with tissue behind it is one thing but as the bullet is exiting it is another. That is why the bullet is found under the hide on the opposite side so many times. Without a sharp edge getting thru the hide during exit is like 4 more inches of muscle. So a big expanded bullet would have a tougher time going thru the elastic hide then a smaller one. A lot of people do not take in to account the temporary wound cavity but when the area effected is organs or nerves the damage can devastating.
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Post by rangeball on Apr 19, 2011 9:01:06 GMT -5
Thanks. Here's what I'm thinking- a cylindrical copper or hard cast lead bullet that is .40 with a .40 meplat, drilled in the center to accept a plastic/polymer ballistic tip that is the entire nose section of the bullet.
Using the info edge posted earlier about calculating bc for different tip weights based on bullet shape and using the excel program, I get this data-
Data......Copper...... Lead Ogive...... S8 ............ S8 OAL........ 1.6" .......... 1.6" Nose....... .8" ........... .98" Shank..... .8"............ .62" Weight... 320 .......... 320 BC......... .508 .......... .654 SD......... .286 .......... .368 Twist..... 1:16 .......... 1:19
If I remove the tip weight keeping only the .40 caliber bearing surface and replace it with plastic I get:
Weight.. 235 ........... 235 BC........ .356 .......... .457
I'm assuming (possibly incorrectly) that the reduced weight will allow a slower 1:22 twist to stabilize. When I remove the tip weight and calculate for just the bearing surface with a .5 ogive 1:22 is more than adequate.
In theory upon impact the plastic tip would break off and the meplat be left to provide terminal performance, similar to how the lehigh's work I think. Based on 2700 fps at the muzzle the meplat would have a force factor (from the link I provided) of 11.6, and still be moving at 2000 fps at 300yds with a force factor of 8.6, and near point and shoot sighting to 300 yards.
Am I missing something? Such a bullet would be relatively easy to produce once the tip was sourced. In lead it would be relatively inexpensive. Do you think hard cast lead will hold up to this fps in a sabot? Thoughts?
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Post by edge on Apr 19, 2011 10:40:51 GMT -5
First, I think that designing a secant bullet is very optimistic for a first timer! IMO, go tangent first.
Second, design a bullet that is known to be stable in your twist rifle.
IMO, you should have a portion of the ogive in your brass section and the tip as perhaps the front 1/3.
I doubt the tip will just break, hence the advantage to lead. Plastic will need to move rearward. Probably shearing off a small ledge and perhaps expanding a thin brass wall.
edge.
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Post by rangeball on Apr 19, 2011 10:50:40 GMT -5
Thanks. I have been accused of being overly optimistic more than once I was just trying to max the bc in a design that will work in the twist rates out there, most commonly 1:22. I'm not sure it can be done with a lead tip while maintaining adequate bearing surface within the established weight goal. I have some thoughts on the plastic tip, such as making it a hollow point so that it splits into sections and falls away as the bullet drives through, but I have doubts as to if it will stand up to air resistance when traveling to the target.
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Post by rossman40 on Apr 19, 2011 14:46:31 GMT -5
As I used to tell the guys with the PHDs, it ain't over till the fat lady sings. When dealing with ballistic calculations every thing may look good on paper but when you get to the real world somewhere there was a glitch. Just ask Wile E. Coyote. As Edge said start with something simple as a proof of concept (concept that you can do it). Just a simple copper bullet and see how your calculations match. As far as bullet tips I would see if I could get some from Lehigh or maybe another source may be Berrys bullets, they use a polycarbonate tip in their ML bullet and were playing with it in other sizes. Gilbert Berry is the HMFIC and a real good guy to talk to is Jay Phillips if he is still there. Use the Hornady method, get your tip and then build the bullet around it, Dave Emery admitted to doing that. You want the tip to be a wedge driving into the nose cavity. If you have to cut your own tips I would go with maybe polycarbonate rod, hard and easy to machine. If you get the copper soft enough PVC would work well. You will probly have to do some refining on cavity size and annealing to get the optimum terminal effects. It will be tough to get the same results as a swagged Barnes with a turned bullet. The only company that comes close is a German company called MEN with their SFS bullet, Since these are gilding metal I doubt you will see these for sale in the states.
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Post by rangeball on Apr 19, 2011 15:36:51 GMT -5
As I used to tell the guys with the PHDs, it ain't over till the fat lady sings. When dealing with ballistic calculations every thing may look good on paper but when you get to the real world somewhere there was a glitch. Just ask Wile E. Coyote. PHD? Heck my wife says I'm more of a PIA I agree with you though, just bouncy my thoughts off you guys to see if what I'm thinking may even be possible before I waste time trying. That's the plan, based on the first design, but machinist buddy's shop is swamped and the earliest date to get any done is maybe mid summer. I'm not that patient but may have to be Thanks for the leads, but what I have in mind is much larger and will probably need to be machined. I have access to a manual lathe, may have to buy some solid PVC and try it. I'd like it to crush or somehow fall out of the way upon impact and let the solid meplat do it's thing. Wicked looking. I agree it would be tough to duplicate a good expanding solid, which is why I hope the approach with the big plastic tip will work as it will be much easier to implement. Only one way to find out
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Post by Deleted on Apr 19, 2011 17:11:33 GMT -5
If you could make anything close to your 320gn dream bullet that would be great. It's a big goal but I noticed with the mods. in plastic you dropped alot of weight "mass" . What's it going to hurt if you make your theoretical bullet and send it down a barrel. If you just made it solid lead to start out with it couldn't cost too much. We make lure molds all the time that we pour lead into. MAKE ONE !!! and see what happens. There was another member of the board that said his machine shop guy was not tied up I can't remember who it was though,sorry. Good luck and I hope it works out for you. Greenhorn
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Post by Deleted on Apr 19, 2011 17:35:45 GMT -5
Those shrooms look to be offset.Would a plastic tip that had a cam -like stem that would not only expand but put an angle on the petals upon impact be a pia to make? It seems something like this was done for the guilded ones that are above. Just another thought.Maybe have offset grooves that all come to the center point. Greenhorn
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Post by deadon on Apr 19, 2011 17:53:49 GMT -5
As I used to tell the guys with the PHDs, it ain't over till the fat lady sings. When dealing with ballistic calculations every thing may look good on paper but when you get to the real world somewhere there was a glitch. Just ask Wile E. Coyote. As Edge said start with something simple as a proof of concept (concept that you can do it). Just a simple copper bullet and see how your calculations match. As far as bullet tips I would see if I could get some from Lehigh or maybe another source may be Berrys bullets, they use a polycarbonate tip in their ML bullet and were playing with it in other sizes. Gilbert Berry is the HMFIC and a real good guy to talk to is Jay Phillips if he is still there. Use the Hornady method, get your tip and then build the bullet around it, Dave Emery admitted to doing that. You want the tip to be a wedge driving into the nose cavity. If you have to cut your own tips I would go with maybe polycarbonate rod, hard and easy to machine. If you get the copper soft enough PVC would work well. You will probly have to do some refining on cavity size and annealing to get the optimum terminal effects. It will be tough to get the same results as a swagged Barnes with a turned bullet. The only company that comes close is a German company called MEN with their SFS bullet, Since these are gilding metal I doubt you will see these for sale in the states. Rossman, according to hornady. their GMX is gilding metal,Rusty
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Post by rossman40 on Apr 19, 2011 22:42:41 GMT -5
Gilding metal or tombak (unless your french then it is tombac) is anywhere from 5-20% zinc with the rest copper so technically it is brass. For a US bullet maker it is one thing but for a foreign manufacturer to get a brass bullet, even if it is a rifle bullet, into states it is a whole different matter. Just the addition of 5% zinc basicly doubles the strength of pure copper. For the Winchester Silvertip ammo they added a pinch of arsenic to get the silver color for the jackets.
The MEN SFS (I think they changed it to the SFC now) is actually designed to be able to shoot thru glass. Supposedly the cuts are supposed to match the 1:10 rifling so the bullet drills thru glass without deflection along with being aerodynamic and helping with expansion. The tip looks like a BB on a stem. MEN basicly supplies a lot of the LEO ammo in Europe. They got bought out by the Brazilian Magtech ammo a few years ago but still maintains close relationship with RUAG who owns RWS, Rottweil, GECO, Norma and Hirtenberger
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Post by rangeball on Apr 20, 2011 9:07:16 GMT -5
If you could make anything close to your 320gn dream bullet that would be great. It's a big goal but I noticed with the mods. in plastic you dropped alot of weight "mass" . By using a plastic tip the end result is a bullet that is 70% lighter which still leaves a very high BC by our standards, theoretically, and keeps the final design in a weight that should still allow us to get good speed. Unfortunately I wouldn't have a clue how to go about doing that other than paying to have a mold made which seems expensive just to prove a concept. I'd rather play with copper on a lathe. I think it was wayles, I'd hoped he would join the discussion but from the sound of his last post in his thread I think he had some ideas he was going to work on. Hopefully he'll come up with something. Thanks
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Post by Deleted on Apr 21, 2011 7:53:09 GMT -5
If you get a prototype out of copper you can make a mold "inexpensive" out of bondo it will handle at least 1 hundred pours with lead. If that design doesn't work out try another. I realize with purelead bullets the "Center of gravity" might be an issue,but you should be able to see how a bullet will "fly". Maybe not, but its worth a try. Good luck, Greenhorn
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Post by rangeball on Apr 21, 2011 8:56:51 GMT -5
Did not know that about bondo. Thanks for the info! I put out some feelers yesterday to a mold company, haven't heard back yet.
If hard cast lead is up to the smokeless task up to 3000 fps I think it has merit, if a bullet can be properly designed.
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Post by rangeball on Apr 21, 2011 15:15:07 GMT -5
Was looking at this pic some more- Secant ogives have a higher BC than tangent and seem to allow a lighter bullet weight for a given length. Looking at the nose section of the secant version, it seems to be almost a straight line to the bearing surface with a sharper corner at the intersection than the tangent. How close would the bc be of a long cone? It would seem shape wise to very similar to the secant nose design?
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Post by edge on Apr 21, 2011 16:52:40 GMT -5
A tangent radius almost always has good flow over the area where the ogive and shank intersect. Almost any other transition runs the risk of turbulence which will lower the BC faster than any gain you could possibly hope for with another tip design. IMO, make a tangent radius first...it is kind of your "GO TO" load. Once you have something that works even if it is heavier or not to your perfect spec, at least you have a baseline bullet. IMO edge.
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Post by rossman40 on Apr 21, 2011 20:54:35 GMT -5
I would have to agree with Edge, start simple and get the first batch under your belt. Maybe a simple 4crh tangent ogive with a .060 meplat if you do not want to go with plastic tip. Some where I read a meplat under .17 caliber has no effect on BC (.15 caliber for a .40 bullet would be .060"). I do not know offhand where that would put you on weight. You could drill the meplat to the shoulder, maybe a tad past. Cut you 9 or 12 and go shooting. Maybe anneal them first, over on swinglock.net shows a easy way. Maybe even dump them in a tumbler to polish them up a bit.
You will need two chronos to get your BCs and you will need to measure/survey them in.
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Post by rangeball on Apr 22, 2011 8:51:38 GMT -5
Thanks guys.
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Post by rangeball on Apr 22, 2011 10:12:32 GMT -5
I had sent an email to Veral at LBT molds and this is his response-
Only problem is I'm pretty sure I can't keep the weight between 230-50 with an all lead bullet, even with a soft tip, unless the tip is long with a hollow point to remove weight.
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Post by Deleted on Apr 23, 2011 19:42:40 GMT -5
Are you dead set on that weight range for recoil? How much more would it weigh? The little more mass would only help the bc so you might have to bend a little with your thinking, it definitely won't be the last bug that has to be "worked out". IMO if you could make an all lead bullet ,shoot it at paper, see how it shoots, if good call your mold guy. If bad alter the lead bullets to see if you can correct problem ,if not, make another all lead bullet and repeat process. I'm not saying make a alllead bullet and go hunting with it ,,just shoot paper until you find something promising before you throw down the big bucks. Just trying to help. Greenhorn
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Post by deadon on Apr 23, 2011 20:31:16 GMT -5
Someone waaaay back in this thread mentioned using bondo for a mold. I have pored many lead jigs from 1/4 oz to one lb using plaster of paris. Just two more, Rusty
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Post by rossman40 on Apr 24, 2011 0:26:23 GMT -5
Another one of those balancing acts. You have to get a long nose for BC, then you have your length restrictions to stay with a 1:22 rifling and finally staying in your weight range.
I've been playing at the drawing board and a tangent 3crh will give you a nose roughly 1.5 calibers long which is where you really see a difference but when dealing with lead your getting past your weight limit then if you go with copper and bump to a tangent 4crh nose your nose length bumps to 2 calibers and your getting too long to stabilize with 1:22.
Back in the late 60s early 70s Herters had a "Wasp Waisted" bullet. I think they tried to use it to cut down barrel friction or maybe even a attempt at Whitcomb's area rule, which was ground breaking back in the 50s. While the bullet did not have the "coke bottle" of the F-105 or 106, it would be one way to trim some weight and get the center of gravity forward and maybe be able to stretch the bearing surface. The only thing I would worry about would be if the bullet obutrated crooked, and then how much drag would be from the secondary wave.
Just a note, you find elements of Whitcomb's area rule design on just about every modern aircraft and is being carried over into automotive design. The Kenworth T-2000 semi even uses it.
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Post by jeremylong on Apr 25, 2011 21:37:18 GMT -5
Those wasp waisted bullets look crazy. I found NEI makes a modified version for the cast guys, but it sure doesnt do much for BC. The ring groove close to the rear may do something for obturation though?.. www.castbulletassoc.org/wasp.shtml
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Post by GMB54-120 on Apr 25, 2011 21:57:15 GMT -5
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Post by rangeball on Apr 26, 2011 8:51:21 GMT -5
Are you dead set on that weight range for recoil? How much more would it weigh? The little more mass would only help the bc so you might have to bend a little with your thinking, Thanks, but like rossman mentioned, twist becomes an issue. The design is right on the edge of stability as is.
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Post by Deleted on Apr 26, 2011 9:19:09 GMT -5
OK...instead of hollowing the soft nose,bore out the main core to get your weight where you want it. Maybe drop your poured bullet in a jig with a drill press or milling machine. Maybe i'm being to proactive on this before thinking it all the way through. Goodluck Rangeball, Greenhorn
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