Designing the 2-diameter paper patch bullet.

[Don McDowell]

Could show you what one looks like dug out of an elk...

[Kurt]

Naw to banged up to see what I want see

[J.B.]

I sure would like to see what one of those dual diameter bullets look like dug out of the snow banks

...Sorry Kurt...no snow here ..actually we've barely got any water ... You'll have to wait till June but I can bring a few over for you to test if you dont get any in the mean time. This one will be better suited to the 1/17 twist anyway .

Gavin.

[Kurt]

Gavin you can have some of the moisture I'm getting. 12 3/4" in a week and halve, 9 days actually and more on the way.
If this keeps up into November I won't even get to the shed to get the six foot snow blower out.

I really don't have a rifle I use for matches that a dual diameter bullet will fit the chamber.

[Distant Thunder]

I've been shooting a 2-diameter bullet in my .40-65 for just over a year now and it works very well for me. I would think if I looked I'd be able find one that isn't too banged up. Because that bullet has just a rather sharp step between the diameters it is probably still visible, but I would think that the bore diameter would bump up to pretty much the same diameter as the groove diameter section. That should be something about .403 or .404". The patches come out pretty cut thru to the front edge.

If I think of it I'll look around my 200 yard impact area and see if I can find one, but that wont happen for a week or so. I leave for Lodi tomorrow and I'm in a deep and growing hole at my shop and I need to get things straighten out there before much more time slips by.

[flatsguide]

This is a very interesting read as I have been thinking about two diameter ppb’s for a while now for my Browning 45-70 bpcr. It is shooting 1.25” to 1.375” groups at 100 yds with ppb’s. On post 18, the belted groove diameter section of the bullet appears to be over one caliber long. Does it need to be that long? Was thinking that the groove diameter section in the neighborhood of .125” to .135” long would work. Seated in the case that far would give better powder capacity and the bore section being longer would give better bullet/bore alignment. Also the transition ring at the bore to groove diameter being much further back may contribute to better stability. Maybe with a short groove length band it may strip but they don’t with a bore diameter ppb’s. Also one might have better results with a harder alloy like 1:12 or 1:10. Would like to hear your thoughts on this as I may order one from Brooks. Also if .125”/.135” proves to be to shallow it might be possible to dial in the mold and cut the groove section deeper.
Beltfed is getting nice groups with his two diameter bullets.
Thanks Richard

[Distant Thunder]

I apologize for letting this sit for so long but life can sure get in the way at times, sorry.

So I cut the first mold and after casting some bullets with it I wasn't satisfied with the end results, just not what I wanted. I decided to start over again with a different set of blocks and I made some adjustments in the way I machined the cavity. A this point it looks much better than the first one. The blocks sat there waiting for me to find the time to machine the cavity, which I started late last week and finished today. I'll fit a sprue plate to this mold hopefully yet this week and cast the first bullets with it. It can be very hard for me to tell what a cavity is going to produce until I actually have bullets from it to examine.

   

To tell the truth the mold I use for long range matches doesn't cast perfect bullets and I am amazed how well they shoot every time I shoot a match with them. I plan to cut a new mold to the same dimensions that I hope will cast better looking bullets. Once my bullets are wrapped they look fine. Maybe the patching makes them shoot so well, it at least hides the flaws!

Dimensionally this "second" 2-diameter pp mold is the same as the first one, but the finish much better especially on the nose of the bullet. I do learn something new with each mold I cut and these 2-diameter molds seem more difficult than the straight sided bore diameter molds to get everything just right.

I plan to work on the first mold and make a couple of adjustments so I can use it in my old C. Sharps .45-70 which has about .200" of freebore. That rifle is the only one of my rifles that I have not been able to get consistent results with using paper patch bullets. It should come round with a 2-diameter design. Time will tell.

Hopefully I can finish this mold up for Matt soon and he'll have plenty of time to get his rifle up and running for the 2019 season, which has been the plan all along. I should have some sample bullets next week, that will tell the story.

[Don McDowell]

The cavities sure look like that bullet ought to fly nice.

[Distant Thunder]

Don,

You'd have to look close to see a difference between the two, but the second one has a smoother, truer elliptical ogive. The first one has barely visible short line segments that make up the ogive. It has to do with two different tool paths used for the final cut. My problem with the software I use has always been that one tool path cuts the very tip of the nose better but leaves the line segment on the elliptical portion. The other cuts a smoother, truer elliptical from but does not cut the nose tip radius well and leaves the form a bit blunt.

I finally figured out how to use both tool paths and end up with just the best part of each. I guess I'm a little slow sometimes! The second mold has as close as I can machine the same nose shape of my very successful long range bullet. That's what I wanted this bullet to look like and now I know how to it.

I wish I had more time to make molds, I think I could get it down to a repeatable system, but so many other things keep getting in the way and sucking up my time. Assuming this mold works out I do believe I will be able to repeat the process with the same results. That is my goal. Even if successful I still would not be able to make them fast enough to make a business of it, it would never be profitable. I do enjoy making molds though.

The goal here is to get more information on paper patch bullets/molds out to other shooters and the 2-diameter concept in particular. I really think 2-diameter paper patch bullets have a place in today's modern chambered rifles and there are a lot of those rifles out there.

[Don McDowell]

Jim I think you're right the dual diameter bullets can work extremely well in todays "standard" chamber, and I think they leave a much cleaner barrel than the singe diameter bullet.
I do find that with the dual diameter 45 bullet Brooks made for me that some rifles will shoot them better than they will greasers or regular patched, but I have one rifle that absolutely hates the things and will sling them into the target sideways at 600... Not going to give up on that rifle and dual diameter, even tho it shoots regular patched better than any greaser you can put thru it.. Just has to be a matter of finding the right load/wad combo.