Like My Cherry? Smokeless Paper Patch bullet 45 cal rifle

[windrider919]

This is long but bear with me through the explanation, I cover each important detail of the design so you, the reader will KNOW why each detail was chosen.

I am having the cherry made for a 45 cal cast lead bullet designed for use only with smokeless powder. The design of the smokeless bullet needs to be different because the two different powders operate differently. According to the group members and outside experts I have consulted Black Powder has a ‘sharper’ explosion that obturates or bumps–up the bullet to fill the full diameter of the barrel when the gun fires. Smokeless does not do this as much, so a BP bullet can and should be bore size or undersize. The Smokeless bullet is “sized down” instead of being bumped up in diameter as it is launched forwards into the lands and grooves. The Smokeless bullet will experience higher pressures and most probably be driven to higher speeds also. I designed this bullet to try to approach jackated velocities. To prevent blowby the diameter of the bullet must be slightly larger so that the two wraps of paper diameter is just above groove dia. Example: .459 to .460. The soft lead and paper will ‘crush’ down easier than a jacketed bullet would so no excessive pressure should result from this. Also, many of the more modern chambers are fairly large in the throat area. For example, my .458 Winchester Magnum measures .463 in the throat area just in front of the case and before the land leed. It usually takes a chamber cast to discover this so most people are unaware of this accuracy robbing fact. So the more the bullet fills this space the truer it will launch forwards. Jacketed bullets seem to travel through here OK, they must not cock as much as soft lead bullets sometimes do.
Other factors affecting the design are: At BP velocities the PP stays on excellently as it travels down the barrel. At higher speeds and greater pressures the PP does not work as well, loosing accuracy so there needs to be something that holds the patch on better. The ideal of PP was / is a smooth, more aerodynamic bullet. So it was suggested that many small grooves would have less drag n turbulence than a couple of large grooves would. Again it was recommended that something like the Ranch Dog or the Lee Tumble Groove design would support and guide the bullet down the barrel while sealing gasses / preventing blowby. Hence the target diameter of the smokeless bullet will be .453/4, and the final PP diameter will optimally be .461 / .462.
Next, I have shot a lot of 500gr plus bullets and I finally decided that it was great fun to launch huge gobs of lead downrange but at the end of the day it was too much on this old body. But I found that the 400gr bullets were just as fun to shoot but much less punishing. And the lighter bullet launched faster gave satisfactory downrange performance. Like a lot of people I talked and wrote to, I am also looking for that magic bullet that will be accurate for target shooting and multipurpose in that it would be suitable to hunt with. Great big meplats are renowned for being hard hitting but even a non-expanding RN 45 calibers frontal area is better than a lot of jacketed calibers after they have mushroomed. A pointed nose is more aerodynamic and flatter shooting, and with a higher ballistic coefficient will be longer ranged. They also feed better than flat nosed bullets. If Ranch Dog would have a version with less meplat and more point I would buy from him instead of trying to make my own. Anyway, hard recoiling rifles are notorious for flattening the bullet noses against the front of the magazine well. I noticed that if there was a small meplat it stood up to the battering almost unchanged versus the rounded or pointed nose. Plus, the mould makers said that a meplat was easier to make then the pointed shape. Finally, comments were made to the effect that we PPers usually shoot a fairly soft bullet, ranging from pure PB to maybe 20-1 tin and that a small meplat will cause more mushrooming than no meplat whatsoever. So my design has a small meplat.
There is a slight change in diameter on the nose from .442 to .450, a little shoulder {not shown on the drawing}. The PP will be started just slightly forward of that shoulder on the smaller diameter so as to not be damaged by the lands. It leaves the start of the PPed diameter under bore diameter. Sort of tapered like other styles of PP bullet which helps the bullet to enter the rifling without damaging the PP. And the little shoulder on the nose is supposed to help airflow around the bullet. After the .450 'bore riding' section which is .100 long the diameter increases to .454 and this section is all Lee tumble lube groove style for .500 of an inch. After the bullet sheds it’s patch, the small tumble lube grooves should have less drag than conventional grooves. Total barrel riding length is .700 which was again indicated as the correct ratio for a better 45 cal bullet. Smokeless PP shooters who need the grooves to help hold the paper in place also frequently lube the grooves just like a conventional cast bullet so it sort of glues the patch in place a little. Most told me that they do not size them however, just lube. A benefit of the lube, even though it is under the paper is that it somehow reduces blowby better than dry PP bullets.
And finally, the bullet base. Remember that the base is one of the most critical areas of a bullet. That the squareness of the muzzle and the bullet have a major effect on the accuracy of the gun. That need for a true, square base has created a market for nose pour moulds because those moulds cast bullet whose bases should be perfect. Further reasons for my design, jacketed bullets are frequently boattailed for better aerodynamic performance. Combining the squatness needed on the base with the better BC leads to one solution, the rebated boattail. And here an advantage is that the little imperfections in a base pour bullet disappear, the rebate shoulder is a part of the consistent, square mould and the cutoff spru is on the boattail base where any mild untrueness does not affect leaving the muzzle or the airflow in flight. I am soliciting comments and I have considered just going with a flat base and not getting 'too' experimental. But I really want to try the boattail and will not change it unless one of you can show me that it absolutely will not work.

How will it perform/? I / we will not know until I have tried it. Lots of experimental projectiles have been made down thru the centuries since firearms were invented. And lots fell by the wayside as unworkable too. That’s why this is such a fascinating hobby. All I can claim is that I did a lot of research, talking to many other shooters and combined the knowledge they gave me to make the ‘universal big bore smokeless PP bullet’ or at least what I think such a bullet would be like. I have wondered why no one else hasn’t already done this so I could just buy the mould but either I am a very original thinker or I am so far off the road that I fell off the map.

Like I wrote in the beginning, I am having the cherry made and if any other smokeless PP shooters would like to try this theoretical bullet we could make it into a group buy where we use my cherry to make their moulds. I thought I might hold off ordering the cherry and mould until I could get some feedback from my fellow shooters.
I explained everything about the design reasons but more heads are better than one and if I have made any major, project killing bad errors I thought you guys might point them out. The design is a mix of traditional and new so it takes an open mind to not automatically reject it. And that type of mind is what I think we have here at Cast Boolits. I do not want to re-invent the wheel by changing so much that it becomes just a traditional bullet. You know , “You should eliminate the grooves, make it smooth sided.” “Use pure lead instead of any alloy,” “Its good to swage the lead to eliminate any voids.” “Instead of PP you could use cupronickel instead.” “Etc”, until what remains is a standard jacketed bullet. I’m not going down that path. Anyone shooting smokeless, high velocity PP loads interested in joining this path?

Here is a link to a drawing of the proposed bullet:
http://i290.photobucket.com/albums/ll249/windrider919/458WinMagbulletdesignV2.jpg

P.S. - I am having a double cavity mould made and the 2nd cavity will be the SAECO # 176-487, a 350gr, .459 dia, RN-FP-GC.

[duke76]

I would be intersted, dependent on price of course, although I would prefer a little heavier Todd

[windrider919]

The weight at 425gr should give good long range performance because it gives a good ratio between length and diameter aerodynamically but produces less recoil when pushing a bullet at 1900 to 2200 FPS. A 500gr bullet just hurts me too much from recoil. Its a compromise, if I could have gotten the long rang performance in velocity and drop with a 350 grain i would have been happier but it just isn't possible. It takes 425gr to do it.

[leftiye]

Should work. Paper patched boolits before patching should be bore diameter to bore diameter plus .001". If this is a .458 caliber, it's a little too big. I've got an H&R that's .452 bore diameter, standard size should be .448" - .449".

As for grooves, what you've got are tumble lube grooves like Ranch Dog puts on his boolit molds. These will work fine, but much narrower, and much shallower, say .050" wide lands and .030" wide grooves .010" deep would work fine too. Long range Bp shooters like plain boolits with no grooves. They like undersized boolits that "bump up" with the shock of ignition (explosion with shock wave) of black powder. This (no grooves) will work fine with smokeless too if there is a provision (ogive shoulder) for wrapping the paper so that it will not tear off or bunch up as it is engraved in the rifling. Gripping the paper in this instance would be improved with a slightly rough mold or as cast boolit.

The boattail will not have much effect until you're at subsonic velocities (believe it or not). I'd dispense with it.

[Buckshot]

..............It's experimental, and that means it has to be experimented with, to see if it all adds up. If it shoots as well as a conventional boolit core for PPing, then no net loss. I can't see anything in the design that in my experience would spell instant disaster.

Rifling twist requirements are pretty well understood by most anyone. Rifling DESIGN though, is something that has been experimented with since it's inception. Each one is supposed to have been an improvement over the mainstream forms, yet only a few continue in major production continuously, with the old 'Oddities' showing up on a whim from time to time.

Bullet and Boolit design can be added to the "Pretty well investigated" arena along with rifling form's. After the patched RB, look at what has passed from favor in cast lead (enlongated projectiles), and those that remain in production to this day, design wise.

Thoughts on your design:

The beauty of the patch is to allow a softer alloy slug to be driven to much higher velocities while maintaining good accuracy. I can see yours doing that too, compared to a similar alloy GG slug.

The boatail feature could add something to the BC of the slug. I'm no ballistition (or speller, either), nor can I computer model but that won't keep me from saying that the meplate may negate any benefit you see from the BT. With jacketed bullets (do they still make those? :-)) I don't think I've ever seen a BT that wasn't on a pointed slug. Maybe I've been sheltered?

Col. Harrison seemed to believe that faint radial grooves on a boolit core's body was a benefit in helping retain the patch while in the barrel. It's in his book, and I think Lyman produced moulds with this feature.

Overall, to me your boolit has good basic lines. It doesn't carry the BC required for long range target use, and the meplat suggests hunting also as a use. It's of upper mid-weight so far as 45's go and should make a fine hunting slug cast soft and patched, and a fine close to midrange target slug. Regardless HOW fast you drive a 45 cal rifle slug (boattail or not) you won't turn it into a varmint rifle.

Depending upon cost (as others have mentioned) I would certainly be interested in trying one. As I said, I think it will make a fine slug but also being honest I don't think it will make an earth shaking difference over the PP slugs currently available. There were some very canny inventors and well financed experimentors at work on this in it's heyday from 1850 to 1900. Since then maybe not so many, but no less capable or driven. Not to say it's not worth trying.

I won't be as dumb as that patent office supervisor in the 1880's that suggested they might as well close the office, because everything has already been invented :-)

................Buckshot

[405]

Takes courage to step out there and let folks take critical review.:drinks:

CORRECTION! My mistake! I misread your previous numbers Red River Rick's excellent schematics brought that to my attention- :coffee:

The basic as-cast diameter of the PP bullet at .455 seems too large for most applications and chambers. With beginning diameter of .455.... thin papers will bring the bullet up to about .461/2. That diameter works for some chambers, throats, bores using normal lubed non-PP bullets but may cause some problems for tighter chambers, throats, bores. It would not work as-cast in either of my Sharps. It would work in my oversized Trapdoor as explained below. But 'tis much better to start large and size down than start too small and have no where to go :mrgreen:


For the diameter of the standard grooved, GC bullet might think about a drop-from-mold diameter of something like .462. That way the bullets would be useful for even the over-sized bores in some older rifles like the trapdoors. I know... I have a trapdoor with an excellent bore but the groove diameter is.461. If the caster wants a .458 or .459 bullet then just push thru the correct size die. Lee dies work great for this with no problems and near perfect concentricity.

PP bullets that have a smooth tapered transition between bullet shank and nose ogive the paper patch does in effect provide some bore riding characteristics. The weight of the bullets (regular cast design and PP) seem fine as does the bearing surface length of .700 for the PP.

While the small boat tail may work a little to help BC I think it may hinder a neat tail twist or tuck for the overlap paper and would complicate using a base wad between powder and bullet if used in BP loads. For the smokeless loads, while it is anecdotal in nature, there is some evidence that a boat tail or bevel base may hinder full and even obturation. I don't know for sure tho.

About the small lube grooves.... similar to the Lee and RD styles.... I don't have enough experience in paper patching those bullets to say much. Seems plausible that it would decrease friction down the bore and may have benefit for carrying extra lube but I surely don't know.

Hats off to ya and good luck. If it works well.... all PP shooters gain!

[4570guy]

After looking at your drawing, I too would dispense with the boat tail. The boat tail as you have it currently drawn does not have sufficient fineness ratio (length to diameter) to do you any good, and it may actually hurt overall drag. The angles are pretty steep as you have them currently drawn. I'd go with a flat base.

[windrider919]

What keeps comming up is the difference between BP and smokeless PP requirements. Several people have mentioned that bullet diameter should be bore or undersized which is true for Black Powder. Shooting Smokeless does require either a thicker PP ...or a bullet large enough that a standard thickness PP on the bullet is just at groove diameter or just above. As I explained, another very important factor is the fit of the bullet OD to the chamber diameter. Again, this applies to smokeless, not BP, the books and some excellent shooters say that the bullet can and should be larger than groove size so as to fit the chamber, which in my case is .463. So a bullet of .454 + .008 PP = .462 which gives chambering clearance. I experimented with .463 but had jams too many times where the PP was damaged and would not let the cartridge chamber fully. Dropping back one thou stopped the problem.

The comments on the boattail have been interesting. It is true that it only works thru some of the flight regime but then it makes a big difference on the BC calculations. And the comments that the bullet is too short to have great BC is true too. In this case I am trying to even out things by gaining some here while losing somewhere else. However the general consensus is to get rid of the boattail and go flat base. I do not like the hollow base because many of my loads use wads which do poorly used with hollow base. The other reason for the boattail comes from the balancing industry. A spindle shape balances better than a cone, its why a spinning football flies true. In this case the nose is one end and the boattail is the other. Like I said, it is an experiment. I am wavering on changing the base still, lets see if any one has any other arguments pro or con. One of the best points is that the boattail is too short for best effect. Absolutely true! Here I chose to make the bore riding surface length override the boattail length yet still keep the weight under 425gr. Many, many, many compromises here.

Another excellent point someone made is the damage the small meplat does to the drag and BC. There is a reason it was done that way. In my research I did find experimental data on bullets that had been damaged by mushrooming in the magazene in recoil. An old NRA article I found had testing of soft point bullets 'flattened' simulating recoil damage and the group size increases significantly. Just like 'slump' of a too pointed lead bullet on firing, the results are unpredictable and cause increased group size. Here the small meplat simulates even, concentric 'damage' so as to still give consistent accuracy. Lose a little here, gain a little there.

On thing about this, sometimes tradition can obstruct progress because "it is not like I am used to so it must not be right or work". I have spent a lot of reading and researching and trying to find if anyone has tried this sort of thing before and I could not find ANYTHING much. What I did find was a lot of "well someone must have tried it in the past and since we do not do that now it must not work". But what I did not find was where it HAD been tested and failed!

[4570guy]

I discussed your bullet design with one of my co-workers (another engineer) and we both agree that your current high angle boat tail will actually result in increased drag. You need a higher fineness ratio on that tail if you want to cut base drag. Otherwise, go with a flat base.

[windrider919]

Here is an email I just sent to the mould maker. As I see it the best way to test would be with two different bases with all other factors being equal.


************************************************** ***************
Hi Mr Rowles,

I sent you a letter yesterday containing the details of a bullet design and a money order for the cherry. Meanwhile, I put the design up for comments on the Cast Boollits forum on the Group Buy section under the title "Like my cherry". Gotten some good replies and some of them made me think.

Most often the concern was with the boattail. I agree it is too short to be greatly effective. And it only works in subsonic flight but then again, ALL bullets reach sub sooner or later. It does "balance" the nose just like a spindle shape flies
truer than a cone. A football is an example of a spindle flying true. There was
some concern that the rebate would not clear the muzzle square enough and that the exiting gas would tip the bullet like happens with bevel base bullets. However, I think some of the resistance to it is because it is strange and different. Most guys have only delt with flat base bullets and thats all they feel comfortable with.

So I had a idea. To truly test it would require shooting two different bullets in
competition with each other. They would have to be alike in everything but the one factor being tested. So, tell me what you think:

SO, Instead if my second cavity being a 350gr RN-FP-GC bullet, let me change it to a sister to my design.

One would be just as you see on the main drawing. The other would be the same weight and nose and body except that it would be a flat base.

I think that first you would cut the FB cherry, use it to cut that cavity, then further grind / modify the cherry to the boattail and use it to cut the other cavity.

Is this possible? Would you do this so an experiment could be done testing the base effects?

Here is a link to a picture of the FB bullet. Comments? Yes? No? Let me know, thanks.

http://i290.photobucket.com/albums/ll249/windrider919/458PPaltbase.jpg

************************************************** **************

Thanks to all who have responded, as you can see, you opinions carry weight enough to change my plans.

Hmmmmm .... Weighty opinions....cast lead bullets....lead is heavy...........
.................................You are all HEAVY DUDES................. Thanks

[4570guy]

I will be interested to see how your experiments turn out.

[Red River Rick]

Windrider919:

I took your drawings and drew up this 3-D rendering of your design, makes it a bit easier when you have something visual.

The ogive radius is probably not correct, but based on what dimensions you did have, I played with some numbers until it was close. The rest of the dimensions are as per drawing.

FYI, the total volume is 0.1588 cub.in., which gives you a bullet weighing in at approx. 455 grs. (based on pure Pb). The "Boat-Tail" portion has a total volume of 0.0082 cub.in (23.5 grs less if removed).


http://i40.photobucket.com/albums/e239/RedRiverRick/Moulds%201/SmokelessPP.jpg

http://i40.photobucket.com/albums/e239/RedRiverRick/Moulds%201/SmokelessPP2.jpg

Hope this helps.

RRR

[Lucky Joe]

I am afraid I cannot contribute and I'm hesitant to even post this for fear of breaking this train of thought by those involved. I'm simply going to say this thread is fascinating the input and cooperation from the members is admirable. Now I'm starting to get the PP bug. Wish you all were my neighbors. :-D

[smokemjoe]

If you sized the bullet with the paper patch on it would the boattail give you any trouble? But what they said back in the 60s that wouldnt work, today it does, Good luck. I like it. Joe

[windrider919]

Wow, Red River Rick, That is Awesome! I am not computer or CAD literate enough but when I saw the 3D solid I felt such a rush because it was such a fine picture of something that has been only 2D on paper and 3D only in my mind. Also, having had the input from over 12 members in private messages, mostly about the boattail I really believe it should be eliminated. And doing that would bring the weight back to what it was supposed to be.

All this help just proves that this is a great group we all belong to!

Now I am thinking how one would test two different bullet shapes that must weigh the same. The only way I know is a void or cavity in the bullet where it would not effect aerodynamics. Not a final idea but: A boattail with a hollow base?!?! And the Flat Base really could not be so due to it being a different length, perhaps it would have some small cup to compensate. This is going to take some thought and may be too much for now.....I want a mould SOON so I can be shooting. Might have to make that design change in a second mould later.

[longbow]

Your bullet design looks good to me but I have to say I am not an expert by any means.

It seems to me that many .45 cal. cast bullets of RN or RNFP design have very high ballistic coefficients. Your design should be as good as or better than a blunt RN or RNFP design.

Maybe Tom Myers could help out here. He has posted several bullets designs along with weight and calculated BC.

Here is his website: http://www.uslink.com/~tom1/index.htm

Here are some long range cast bullets Mike Venturino wrote about: http://www.shootingtimes.com/ammunition/STcast_040306/index2.html

Maybe the length to get high BC would make the bullet too heavy for you but none are pointed designs.

Another thought about your boat tail ~ if you had a nose pour mould made with a "base pin" like the one Red River Rick shows here: http://castboolits.gunloads.com/showthread.php?t=27252&page=2 you could try your boat tail design, a "standard" boat tail design, flat base or cup base just by changing the base pin. The mould might have to be a minie style mould and single cavity but it would allow all those tests to be done with minimal cost in changing just base pins.

Attached is a picture of a subsonic .45 cal bullet for .45 ACP ~ it has a more conventional boat tail but it must work or it wouldn't be there. I can't remember where I got it from and it may not be relevant to your design requirements being supersonic for the most part but it is a cast bullet with a boat tail.

Also, as for the grooves, I found that my .303 British didn't like a slightly undersized smooth sized bullet no matter what paper thickness I used so I tried grooving it with a tool I made (kind of annular knurling) which makes very small grooves and bumps diameter by about 0.003". That worked well. I am not sure if the larger diameter or the grooves gripping the paper, or both are responsible but it worked and accuracy improved dramatically. Pic of 2 grooved bullets attached.

Good luck and keep us posted.

Longbow

[windrider919]

Sent the check to start the mould machining.

FYI Old West moulds DOES do group buys. in fact he told me that he had to finish a couple of them first before he could start on mine.

[windrider919]

Kool Bzns! - Got an email from a guy who visited our site. Based on his header info he must be in Afghanistan. He was explaining to me about shooting VLD (Very Low Drag) bullets at long range, 1400yds and such. He did not say but guess what I think he does.

Anyway, what he said is that muzzle blast acts to tip all bullets but has a greater effect on bevelled or BTs. Because this about PB bullets I will not go into the details here he also explained why a jacketed BT is affected differently. He told me the cure is simple though. A well designed muzzle brake / compensator which deflects the gas sideways so only a low pressure is left in line with the barrel and does not push past the bullet as it leaves cures bullet tip. The comp he described does not have holes along its full length but only the first half, then the sides are solid again. I could not copy the picture but it looked about 4 inches long with fairly large holes from the barrel muzzle for about 2 inches, row of three holes, then row of two holes. He said that the clearance between bullet and front section was .004. Interestingly enough, I know some adult air rifle shooters who use something very like called a 'Stripper' or expansion chamber which they claim to drastically improve pellet accuracy. Wow! I can see it now. A comped BP muzzle loader!!

His conclusion was I would be wasting my time with a cast BT without the brake.

[35remington]

Shooting a paperpatched bullet through many muzzlebrakes would be hard on the brake, I believe.

[longbow]

For reference, here is an article from Corbin on rebated boattail bullets:

http://www.corbins.com/rbt.htm

Not disagreeing with what has been said, just more info to consider. Your design is similar to a rebated boattail and since the bevel portion is quite short I doubt your design would have the same unbalanced forces a standard boattail might see.

Also, I agree with 35remington on paper patch and muzzlebrake.

Again, if you got a nose pour mould made you could experiment with several different base designs at little cost.

[windrider919]

I was poking fun on the muzzleloader thing. Can't see that one working. Interesting idea on the nose pour with adjustable base form though. A person could have every tail shape imagined all in a single mould.

I went to the Corbin site link 'longbow' had in his post. Very interesting. I had looked at a lot of aerodynamics papers by doing web search on university sites. Here is a lot more and it is all conveniently gathered and explained. The length of "L" is still questionable, mine was pretty short as discussed. Perhaps if replaced and lengthened it would work after all. The goal was a PP bullet that would perform at both short and long range, super, trans and sub sonic. I had said that I had not found much where people had tested this concept, just a lot that said it did not work. It looked a lot like 'Traditional Inertia" resistant to doing anything new. More to think about

[longbow]

Before getting to deep into this, especially financially, you might consider getting someone to run your design through a bullet design program.

I mentioned Tom Meyer in a previous post as I have seen several designs he has posted along with weight and ballistic coefficients calculated by his computer design program. Possibly he or someone else here could do that for you to determine whether the boattail will add much or not. I have no idea what the cost would be but it might be money well spent.

Many of the long round nose .40, .44 and .45 cal bullets have amazingly high ballistic coefficients. Lots of BP shooters shoot long range with heavy bullets at moderate velocity. You could take one of those proven designs and add the boattail to see what the program spits out for ballistic coefficient.

If you scroll down this link you'll see what Tom can do: http://castboolits.gunloads.com/showthread.php?t=30340&highlight=tom+myers

The program results could help you decide on final design if you are going to get a custom mould cut. It should point out what size and angle boattail is required to be effective ~ of course I am assuming it will work with boattails. If it all looks good you could go ahead and get a double cavity mould cut with confidence. If not then the nose pour with base pin would allow some inexpensive experimentation.

It would certainly be interesting to see the comparison between bullets with and without the boattail especially at long range.

You know I can't help thinking I have seen a PP boattail bullet before but I can't remember where.

These are sabot bullets but have a short boattail: http://www.thebuckskinner.com/blackpowderbullets_dc.html

And these: http://www.barnesbullets.com/products/muzzleloader/spit-fire-tmz/

Wait a minute! Here it is on Brent Danielson's site: http://www.public.iastate.edu/~jessie/PPB/PPB_files/Page1187.htm

The page doesn't seem to be working well as I can't get it all in view - no scroll but you can see the boattail on the lower left.

You might try contacting Brent, he has posted here recently. I'll be he can help you out with design and performance info.

Longbow

PS: Ha! I take it back, if I switch to authour mode the page works fine (I use Opera so maybe that was my problem)

[Tom Myers]

Following is a copy of a reply to an email containining some questions I received from Windrider that he asked me to post here on the forum.

Hello Carl,

I have been following the discussion a bit and I tend to agree with most of what has been commented on.

I think that the most salient objection to a rebated boattail on a cast bullet can be reinforced by the experiments performed by Brent Danielson and documented on his website along with this comment "One other curious thing about this particular bullet. The shaft of the bullet just ahead of the boattail rebate seems to be flared. Almost as if it's skirt is being blown up. Not sure how this can happen but it certainly did. " .

I believe what is happening is that the slope of the boat-tail ramps up the pressure wave of the combustion gases kind of like a tsunami wave and, as the bullet leaves the barrel, the majority of the pressure is concentrated on the rebated portion, thereby distorting the soft lead alloy base rim and destroying any accuracy inherent in the design.

The cast bullet drawing software does not calculate the effects of a boat tail on the BC. However the Ballistic Coefficient Estimator software on my website does estimate the relative effect for Jacketed Bullets:

This is not a precise calculation, but is an algorithm that I developed to fit the various differences in Ballistic Coefficients that have been published for a great many commercial bullet

One first determines the Form Factor of a bullet from the published or known BC in this manner

FF = Bullet Weight in grains / 7000 / BC / Caliber / Caliber.

FF = 437 / 7000 / 0.3041 / 0.455 / 0.455 = 0.99162

Then a correction factor for the form factor is calculated in this manner

1 minus The Cube Root of ( Boat Tail Diameter / Caliber) is determined and then is multiplied by the Boat Tail Length and is then divided by the Boat Tail diameter

( 1 - CuRt( BTD / Cal ) ) x BTL / BTD

( 1 - CuRt( 0.255 / 0.455 ) ) x 0.100 / 0.255 = 0.068834

The Form Factor is then multiplied by ( 1 minus the number ) to obtain the adjusted Form Factor

1 - 0.068834 = 0.931166

0. 931166 x 0.9962 = 0.92763 = The adjusted form factor

Now the format for finding the ballistic coefficient from the Form Factor is

BC = Weight / 7000 / Caliber / Caliber / Form Factor

The new BC adjusted for the Boat-tail is

BC = 437 / 7000 / 0.455 / 0.455 / 0.92763 = 0.32507

A boat tail of these dimensions resulted in a theoretical 6.9% increase in the ballistic coefficient and this would be even less than that with a rebated boat tail.

In my estimation, a better approach might be to add the length of the boat tail to the nose of the bullet, thus increasing the length of the radius curve or ogive which results in a greater increase in the Ballistic Coefficient.

I am enclosing the dimensional analysis and image of your design and then taking the liberty of enclosing a dimensional analysis and image of what one might do with the bullet that would keeps the weight down in the neighborhood of your recoil tolerance and still retain the secant ogive of your design which also results in a substantial increase in the theoretical BC.

The changes are by no means a recommendation, and are only offered as an alternate consideration base on trial and error throughout 8 years of attempting to place 15 shot inside a 24 inch circle at 1000 yards with a 40-65 Black Powder Cartridge rifle.

Let me know if you have any questions or concerns or if you have any comments.

Respectfully,
Tom Myers
Precision Ballistics and Records (http://www.tmtpages.com)

http://www.tmtpages.com/LinkSkyImages/forum_images/WindRider/WindRider_Design__Rot.gif

http://www.tmtpages.com/LinkSkyImages/forum_images/WindRider/WindRider_Design__437_gr_Sketch.gif

http://www.tmtpages.com/LinkSkyImages/forum_images/WindRider/WindRider_Design_441_gr.gif

http://www.tmtpages.com/LinkSkyImages/forum_images/WindRider/WindRider_Design__441_gr_Sketch.gif

[longbow]

Sorry Tom I misspelled your last name but I knew you were the right guy to consult anyway.

Impressive stuff. Really impressive.

I hope windrider919 carries on with a design and keeps us informed. That's what I like about this site, lots of people trying things and sharing information.

Tom, I have a question for you. Lyman lists the BC for the 457121 (433 grs.) as 0.430 for intermediate velocities. Since it is about the same weight as windrider919's design and has a large meplat is that realistic? It seems very high. Just curious.

Longbow

[Tom Myers]

Longbow,

When I first set up my algorithm for the esitmation of cast bullet ballistic coefficients, I made extensive use of Lyman's BC chart for their cast bullets. I could not use the data from 457121 as it would not fit on any curve that I could make.

The Precision Cast Bullet Design software calculates an estimated 0.3218 for the ballistic coefficient of that design weighing 433 grains.

Tom Myers
Precision Ballistics and Records (http://www.tmtpages.com)

[longbow]

Thanks Tom.

Longbow

[windrider919]

After consulting with many individuals in the group and some expert advice and mathematical calculations and even their expertise in the word of CAD 3d solid images I have finalized on a design and sent it on to Bernie at Old West Bullet Moulds.

[windrider919]

Many thanks to Tom Myers for the work he did. Its guys like him who reach out and help without asking for anything that make this such a great sport. He invested his time and trouble and I owe him a big 'Thank You". We build on a foundation of others, without them we would never progress.

[windrider919]

Bernie at Old West is 'snowed under' and thought it will be as much as a month for my mould. I think that is an amazingly short time. He said he is working seven days a week to fill orders.

It occurred to me that although I have no production lead pot I might run a batch or so off for interested shooters trying PP smokeless. If they will agree to provide / post load and accuracy results here on the forum ( here on this thread or we could start a new thread ). What my goal is to shoot an as cast, no sizing or lubing PP bullet at velocities of up to 2K. I could cast a 100 or so of 20:1 or ACWW to test. The only problem is shipping, I can't afford to do this for more than 3 or 4 people.

If you are following / contributing to this thread then I certainly think you would 'qualify'. Post here and let me know.

[longbow]

windrider919:

I was looking through some of my saved sites and wound up here:

http://www.bpcr.net/site_docs-results_schedules/documents/Dan_Theodore_Boattails_for_BPCR.htm

And guess who made the mould ~ Old West! Might be good to look through if you have time before finalizing your design.

Maybe even contact Dan Theodore for info.

Longbow

[windrider919]

When I first contacted Bernie at Old West he said that he had made a lot of different bullet designs. I said that it would be nice if he had a web page showing all the different bullets he had cherrys for. He gave me the std reasons of no time and week computer skills as to why not. I probably would have just stopped there with the bullet on the thread you show because as Dan Theodore writes in the first paragraphs, as to the design goal, that is what i am trying to do, except in smokeless PP instead of BP. The funny thing is , is that I spent weeks of nightly research on the computer and never found some of the things some of the guys on the forum have shown me. we all live and learn, as the saying goes.

I am still going with the design that Tom Myers polished up from my design. I gave up on the boattail because so many people gave me good reasons not to try it. But was that because my boattail was no good or was it because ALL boattails are no good.

Here are some interesting links to VLD bullets sent to me by that guy in Afghanistan.

http://www.gsgroup.co.za/02hv.html

http://www.lehighbullets.com/products.asp?cat=17

http://lima-wiederladetechnik.de/english/english_rifle_articles.htm

and especially fascinating for long range shooting was:

http://www.lima-wiederladetecnik.de/english/lm-class-bullets.htm
Talk about exotic boattails! This part req. a German converter, downoad from Microsoft but the pictures tell the tale

An unachievable but fun to try goal would be to produce a VLD cast PP bullet, taking into consideration the slump of pointed cast bullet noses and other things.

[TRX]

If you have access to a lathe, you could cast up a batch of normal bullets and machine the bases to various profiles to find out exactly what worked before having a mold made.

[windrider919]

TRX, I have actually tried that and it works for jacketed bullets but not so will for cast. Either the chuck distorts the bullet or the bullet slips and the cut is uneven. I have tried brass to make solids to test but the cost quickly becomes exorbitant. And again I am re-inventing the wheel, lots of professional people with real test equipment have done all this, it's just tracking down the data that has been hard. Like the earlier post where Dan Theodore did design testing with the same goal as I have. Now "All I have to do is get his final results" which sounds so easy but real world is harder. But when I started I did not know I was following exactly in his footsteps. Really, I do not want to be a pioneer, I just want to shoot straight and hard and better than before.

[windrider919]

Its been a while but I went back to this old thread where we designed this bullet. I have been ill and in and out of the VA hosp in Houston and have not had a chance to shoot anything but a couple of groups. I shot at Baillys House of Guns and they do not allow you to go down range and recover targets so no group pictures. You have to chart on graph paper as you shoot. Sorry.

The bullets as cast with 19lb WW + 1lb tin came out 460gr. As you might remember, the small groves were to help hold the patch in place at high SP velocities. I am wrapping with 100% cotton typing paper , with a 75% water, 25% Rooster Lube solution. More lube and the patches stick, causing fliers, less and the high humidity during the summer and the patches unwrap. I am shooting as cast and wrapped. A wad cut from PE plastic milk jug is placed under the bullet. I 'neck size' the case for 3/8" then use an oversize expander to give me just enough neck tension to hold the bullet against finger pull. Otherwise the cases are not sized since they are only fired in one rifle. I 'debell / crimp' the case mouth to return it to straight but not curl in and cut the patch.

Standard cooling and cleaning procedures were followed for shooting off the bench. I tried 5744 but it left a lot of grains in the barrel. The accuracy was not all that good either at 2 1/2 inch avg group size. Tried BLC2 and got good accuracy but thought it would be better to go for a more common powder. So I used 4198 and stepped up from 1400 FPS (using the 60% rule) to 1900FPS at which I stopped. I could have gone higher velocity but to be honest, that is the point my shoulder gave out. Also, the 1800FPS group was the smallest of the day. Measured center to center that 5 shot group was just slightly above 3/4 11846inch. Not bad for 458 Win Mag but still not good enough for BPCR standards. The 1900 had opened up almost 1/2 inch, was it because of recoil or the bullets being pushed too fast? Most groups will be fairly tight with one or more drifted out some to elongate it. As I have seen before when pushing too fast, the overall group will be more spread through the group size and that I what I had.