Help me design a 25 cal Boolit, please

[303Guy]

I have a lathe now and want to make a PP Boolit mold for my 303-25. It has a 1-in-10 twist and accepts a long loaded j-word round. I would like to have as much boolit weight as possible but plan to design around the chamber and throat and take whatever the weight turns out to be.

So, where to begin?

[docone31]

My thoughts, and since I plan on patching for my 25-06, it is valid for the .303-25 also.
The jacketed, is .257. If it were me, I would go .252 on the body. I would also match grain weight on the jacketed load that works for you.
From there, I would wrap with two wraps of notebook paper. I would use a cigarette roller for this, that casting is small. I would use standard wrapping techniques.
From there, I would size it.
I would start at .257, then maybe open it up to .258 to tighten groups if neccessary.
By the by, I would make the model castings, complete with lube lands to size down out of steel. I would then cast aluminum around the model(s). I would make a one part mold, and cut it apart, unless you can mold aluminum with a parting line in a non-melting material.
In other words, since paper patching substitutes jacketeds, I would match an existing jacketed bullet, and make a mold to down size, then wrap and size.
The .25s are capable of precise performance.
This one will be fun to watch.
I bet you can do it.

[longbow]

I think the simplest approach is to make a push out mould.

You can ream or bore (small boring bar!) to the diameter you need for patching then turn a sliding nose form. This allows multiple nose forms for different profiles: spitzer, round nose, TC or whatever and also adjustable length and so weight. Very versatile.

I can send you a design for a push out mould. They are about as easy to make as it gets and ideally suited to smooth slugs for paper patching. If paper grip is an issue just roll uinder a file or knurl lightly.

I usually make a D reamer for small diameters and bore larger ones. The D reamer is very easy to make.

If you are interested let me know. I can send AutoCad, .stp, .stl, dxf; or just PDF or jpeg if you don't have drafting software.

Longbow

[windrider919]

The longest bullet that will stabilize in a 10 inch twist is:

10 / .257 = 38.9105058365

150 / 38.9105058365 = 3.855

.257 X 3.855 = .990735 [max length .257 bullet w/ 10" twist rifling]

I would make a simi-spitzer/money bullet nose that is bore riding WITH the PP
and shoot for .252/3 for the major, bore riding core diameter [ie: two diameter bullet]. You should PP to .259 if your throat is standard diameter BUT you have a custom chamber so you need two dimensions. Ball seat/throat diameter {so final PP dia is throat dia - .002} and distance from case mouth to rifling. You should not allow any of the bullet to stick into the case below the neck for PP bullets. So case neck length + throat length ( core dia. .252 for the first two dimensions long) + sharp taper to bore riding PPed nose (lead core dia. = to .250 - .008paper patch = .242 to .243) = max bullet length. The rifling will engage the patch over the sharp, short taper which will extend further with the patch actually riding on the rifling tops by about a .001 until the curve of the nose brings the PP free of contact with the rifling then end the patch.

[runfiverun]

you might want to think about a design with a ton of ribs on it like a lee tumble lube boolit but much smaller and many more ribs to help hold the paper better and make it shred more easily.

[longbow]

That's what I did with the smooth boolits for paper patching for my .303. I made an "knurler" that puts small annular rings (like mini tumble lube grooves) all down the boolit. Works very well for the .303.

Longbow

[303Guy]

Thanks for all the replies! Right, there is a lot to take in and I've been at it all day and have just retired to some medicinal beverages - so my concentration it shot!

So a 1-in-10 twist will stabilize a .99 inch (25mm) boolit! I ran a 22mm boolit through JBM and it came up with a 1-in-11. So there are no twist limitations.

longbow, I would appreciate a design for your push-out mold. Thank you. I have AutoCad. I'll PM you my e-mail address.

runfiverun, it will take me a while to be able to bore a ribbed split mold. But that will come in time (soon, I hope. )

windrider919, I was thinking of semi-spitzer but your spire-points worked so well, I was kinda leaning that way except that the point gets a littlr vulnerable. Anyway, your RN's would likely have done well too if they did not protrude into the case.

docone31, I shall re-read your post in the morrow - too many numbers to focus on right now! I have figured a way to make push through dies to suite my press and a neat way to make tool holders to suite my lathe. (It is not as simple as the digital read-out, better quality lathe I was accustomed to!) I don't have the means of casting aluminium right now. I did try a few years ago when I was working in an aluminium Remelt plant. Not so easy at first!

You know, I don't watch TV anymore. Patching and chatting is far more fun!

[pdawg_shooter]

I think the simplest approach is to make a push out mould.

You can ream or bore (small boring bar!) to the diameter you need for patching then turn a sliding nose form. This allows multiple nose forms for different profiles: spitzer, round nose, TC or whatever and also adjustable length and so weight. Very versatile.

I can send you a design for a push out mould. They are about as easy to make as it gets and ideally suited to smooth slugs for paper patching. If paper grip is an issue just roll uinder a file or knurl lightly.

I usually make a D reamer for small diameters and bore larger ones. The D reamer is very easy to make.

If you are interested let me know. I can send AutoCad, .stp, .stl, dxf; or just PDF or jpeg if you don't have drafting software.

Longbow

I too am interested in your info on a push out mould. I have been patching since the 70s but would like to try building my own mould. No drafting software but some drawings would be great. My address is pdawg.shooter@gmail.com. I thank you in advance!

[303Guy]

I sketched up a mold concept. This one has a parallel shank that fits the neck followed by a taper that fits the throat and a bore riding parallel section that can be varied. The nose piece doubles as the push-out so it would be held back against a stop.

[ra_balke]

You might just consider a 6mm mould from NE, or RCBS ( If RCBC has one ).
Weight between 100 and 120 grains.

OK, why a 6 mm mould..?
It's easy to get .
And it is about 10 thousands undersize, so you could wrap the paper around it, to get the bullet up to size.

Lastly, is a dark part of my mind, I remember reading about a guy who used teflon pipe tape instead of paper, and he said it worked very well.

x

I do have a sneaking suspicion that you intend to hunt with this load.
humm...
If you can get high velosity from your paper patch bullet, you will have a fragile bullet, not a hunting bullet.
If you are willing to accept lower velosity IE 2000 fps, you might as well just go with a cast bullet from WW metal, or 1 to 15 lead tin bullet from NEI, or RCBS at about 120 grains and place your shot.

[ra_balke]

I remember reading in the NRA magazine 30 years ago about high velosity and paper patch bullets. They cut special moulds that had lube type grouves on them, this to hold the paper securely.

They were getting 3000 fps from a VERY hard alloy . These were not in any way hunting loads however.

[Digital Dan]

IMO, you would be better served making a mould that delivers bullets which do not require sizing.

[docone31]

On the calibers he and I wrap, I disagree on smooth sided castings.
My most flawless patched loads were with lube land castings, Aka stock bullet molds, and the worst performing ones were smooth sided.
However, on lower loaded levels, the smooth sided castings started performing, on high levels, lube type castings did much better. Stellar is a word I would use.
On my thinking, in the calibers we are talking here, I think lube lands are a plus. On the larger calibers, there is more parasitic friction between paper and lead.
Just food for thought.
My patched loads with lower loading levels are a waste of time to me. The groups open up considerably.

[303Guy]

Digital Dan, that is my intention.

ra_balke, it is the idea to hunt with them. I do not have to hunt bigger stuff with the 25, for that I have two 303 Brits that need exersizing from time to time!
However, the 25 is such a nice caliber that I was hoping a PP boolit at the heavier end would raise the stakes a little. Thanks for the advice. I appreciate it. It makes sense! Oh well, I was hoping. But varmints are gonna get it! The idea is not to buy anything. Making the bits is part of the fun. It's what 'blows my hair back'!
I have heard conflicting reports about teflon tape?!

docone31, my difficulty is making a split mold. On the other hand, I want to make staight sided boolits work! (Or at least give them a darn good try! )
Now we know it can be done but can it be done by me! That is the question.

Windrider did it! You've seen this before.


I love this pic. One day I am going to digitally remove that flyer! Hee hee.

[Digital Dan]

On the calibers he and I wrap, I disagree on smooth sided castings.
My most flawless patched loads were with lube land castings, Aka stock bullet molds, and the worst performing ones were smooth sided.
However, on lower loaded levels, the smooth sided castings started performing, on high levels, lube type castings did much better. Stellar is a word I would use.
On my thinking, in the calibers we are talking here, I think lube lands are a plus. On the larger calibers, there is more parasitic friction between paper and lead.
Just food for thought.
My patched loads with lower loading levels are a waste of time to me. The groups open up considerably.

Mileage may vary of course. When one begins reducing load density other issues may arise affecting accuracy. Not arguing against your experience but know smoothies work. FWIW, I'd try this (reduced load/performance) in a small capacity case before doing something with a .257 Bob case for example. .25-20 SS comes to mind. My success does not come from reduced loads, never really explored it. I have noticed in load development that accuracy improves as the charge goes up....to a point. I use paper patch for performance on game, not target work....if I was looking for light target loads I wouldn't bother with it.

303Guy, I'd guess you can work with 120 grain lead bullets with your twist but the 10" twist is marginal for J-bullets in that caliber and that weight for a spitzer form. I'd suggest as well that a money bullet nose form will require a harder alloy if you wish to avoid issues with the relatively fast twist. Maybe a flat nose design will do the job with such hardness for hunting, not sure.

[303Guy]

... your twist but the 10" twist is marginal for J-bullets in that caliber and that weight for a spitzer form.

Digital Dan, I've been thinking on what you said. This is my understanding too. A 120gr cast semi-spitzer/semi-round nose would be quite a bit shorter so I'm guessing would work fine provided they will chamber. That's where a bore-rider would come in. I am thinking that with the 25 cal, a softer alloy might withstand quite a high RPM. (Hoping, anyway).

My thinking with PP heavies in the 25, that I would be raising the rifle rating to a 'bigger game rifle'. (Hoping!)
On the other hand, hard, lighter boolits at higher velocity for varminting ... !

[docone31]

Just a thought,
What would happen if you took a conventional .25 cal bullet in the design of your choice, soldered a sprue to the base, then made a box large enough to fit the now potential casting.
Then, get a tube of RTV Blue, fill and pack around the bullet with a top plate to compress the RTV.
You could be able to cast directly into that. If you go reasonably slowly, heat will not be an issue. I once saw a sinker mold that was RTV.
Once it cures, you would cut the bullet out and make alignment cores to realign the mold for another cast.
You like to experiment, you might try RTV.

[303Guy]

RTV can take that much heat? Wow! That would be one way to try out all manner of boolit shapes and sizes. It's quite a mission to make a mold to produce the desired shape. I just made one this afternoon! (It's a base pour, push-out type). I'm just in the process of polishing its interior but I had to stop as it is 'medicine' time'! Well, the 'medicine' has to wait as I'm not finished yet.

[303Guy]

I should mention - I am testing mold concepts on my two-groove 303 Brit. The 25 mold comes next! It takes some practice to get down to those minute sizes! I don't have a small enough boring bar yet.

[longbow]

Small cavities are best cut with a D reamer which is easy to make and can be made in 2 or more diameters too if you are so inclined. They also give you the ability to make multi cavity moulds or more than one single cavity mould and the cavities will be identical ~ at least until you have to re-sharpen, then you will lose a little on diameter.

Here is a link: http://www.geocities.com/Paris/5701/...ipes/tools.htm

And another: http://www.machineconcepts.co.uk/sma...ll_drawing.jpg

I usually turn a piece of medium to high carbon steel to about 0.003" undersize, file or mill to the centerline, harden and temper, then stone the flat until the edges will shave fingernail. What you have is a zero rake reamer. Turn them slow and they will cut steel, brass, bronze, aluminum just fine.

Ideally they should be heat treated then ground to the centerline to avoid warpage which is the reason I make them a little undersize. I don't have a precision grinder or jig so file or mill while soft. They usually warp a little and cut slightly large. If they don't then I lap out a thou or so.

Simple to make and great for making pushout moulds. I rough drill then run the D reamer into the hole. They can be made as a cylindrical reamer with flat end or turned to the shape of the boolit you want then gound to the centerline. You will have to make a small ejector pin then instead of sliding nose form.

Longbow