Designing the 2-diameter paper patch bullet.

[Distant Thunder]

With interest in the 2-diameter paper patched bullet concept growing I have decided to start a conversation about how I currently go about designing a 2-diameter bullet to fit a grease groove chamber. I hope others who have worked with this concept will speak up and add to the effort. My purpose is to increase the understanding of the design and increase the successful use of paper patched bullets in competition and shooting in general.

First I’d like to mention that writing is not something I’m good at, so if anyone feels the need to point my many shortcomings in that area please don’t. Let’s see if we can instead advance the sport and use of ppb. Please just go to the grammar and spelling forums and trash me there.

I can’t really begin this discussion without first acknowledging that Arnie Seitz, aka beltfed, focused my attention on the 2-diameter ppb idea about 2 years ago with his design idea for such a bullet to fit the Browning .40-65 BPCR chamber. When I had my very first black powder cartridge rifle I bought in 1991 rebarreled to .40-65 in 1995 it was chambered with basically a Ron Long design chamber. It shares the long freebore idea with the Browning chambers. I happened to be in the process of resurrecting this old rifle in hopes of using it for NRA BPCR silhouette matches. I was struggling with grease groove bullets in the 18-twist barrel and not really getting anywhere.

I had been shooting ppb in a Shiloh .45-90 (standard gg chamber) and a Hepburn .45-70 (Danielson pp chamber) in long-range competition for about 6-7 years and doing fairly well. I had dabbled in ppb bullets since I first began shooting BPCR in 1991. The idea of a 2-diameter ppb wasn’t new to me and I had in fact experimented with it before, but never as much as I have in the past couple years.

Arnie knew that I was making my own ppb molds when he came to me with a drawing of his design for the Browning chamber. Having been a tool & die maker before retiring I can indeed make molds which has greatly helped reduce both the cost and the time for experimenting with different ppb designs. While I can make molds there no way I can do it in any volume and my success rate is not even close to 100%, probably 50% really. I have cut many molds that ended up being recut into a larger caliber or scrapped all together. Also, it takes me about two weeks to make a mold and it would in no way be a profitable undertaking. There are several skilled mold makers who can make a mold to any design and that is where anyone looking for a mold should turn. I DO NOT MAKE MOLDS FOR SALE! Just so we’re are clear on that.

When Arnie came to me I saw an excellent opportunity to make the switch from greasers in my .40-65 to ppb. So I told Arnie that I would see if I could make a mold to his drawing and that I was hoping to use what we learned from his mold to make a mold for my rifle.

So I started down the road that has shown me that the 2-diameter paper patch bullet is indeed an excellent choice for rifles with grease groove chambers and especially for those rifles that have any amount of freebore. My .40-65 has a .409” diameter x .375” long freebore. I am happy to say that Arnie’s design worked out very well in his rifle and another shooters Browning. My requirements were a little different. I had a longer freebore, an 18-twist barrel, and wanted enough weight to knock down rams with some dependability. Arnie wanted the most ballistically efficient bullet for a 16-twist. So I cut Arnie’s design for him and a different design for my needs. The same basic 2-diameter principles were used for both and both designs worked out well, proving to be very accurate out to 600 yards.

Now I have the opportunity to take what I have learned in making those two molds and many other ppb molds over the past 10 years to help another shooter by designing a bullet and making a mold for his gg chambered .45-100. I’ve decided to post my efforts here for others to follow and add to in hopes of getting other interested shooters who want to shoot ppb to use the information and have molds made so they can have the best possible chance of success. I want more ppb shooters.

This project will take some time, something that I have in short supply, so be patient. I’ll being posting pictures and details as best I can, when I can.

Please feel free to ask questions or if you have other ideas on the subject please bring that up. I hope to include drawings of successful designs I’ve worked with and anyone is welcome to use them as is or modify them to fit their needs.

I am no expert on bullet design or ballistics, but I have some opinions that I have formed over the past 27 years of shooting BPCR and paper patched bullets. I have not closed my mind to new or different ideas, but rather I continue to try any reasonable idea and I have kept the ones that proved true and let go of those that didn’t. I am not done yet with that process and won’t be until the day I put up my guns for good.

As with any information you read on the internet don’t just accept what I say as correct and use the information I present with caution and safety in mind.

DT
aka Jim Kluskens

[Don McDowell]

Jim I wish I had the talent to cut moulds as I would really like to be able to do more experimenting with the dual diameters.
Been messing with them for about 10 years or so, and it seems like to date, if the base diameter is bore diameter to no more than .003 under bore, and a thinner paper is used they surely do serve well. Altho that 45 cal bullet I gave you at Lodi works very well in 9 lb cotton paper from paper mill in the CPA 45-90, other rifles seem to shoot 8 lb better (Seth Cole 55w) with less unexplained dirt diggers.
The dual diameter 40 bullet I had Brooks build is .400 on the base, due to the rifle it's mostly intended to be used in shoots a .400 diameter straight sided bullet the most consistent. Hopefully sometime in the next couple of weeks I'll find out if my plagiarizing of your bullet will pay off or not.

[mherth]

Don, I’m still trying to shoot PP in my GM barrel 45-70 and am wondering who made your 45 dual diameter mold. Been thinking about this dual diameter thing vs breech seating. What are you using for a wad? And how critical is case length vs powder column height?

[Kurt]

A dual diameter would never work in my .40, the chamber is to tight. Arnie gave me a couple of his bullets and patched with .0018" paper they wont even go into a clean fired case. The chamber in little missy will not except a bullet larger then .4033" diameter unless I breach seat them.

I had three of Arnie's bullets and shot them with the scope mounted .40-65 on my 130 yard range breach seated and the three shots covered with a dime would just show one 1/16" crescent cut outside.

Those were the bullets Arnie used at the Lodi match when he shot a 99 at 800. One shot just missed the 10 ring by about 3/4".
I don't recall the bullet length but it's a lot longer then I would expect to shoot well in a 14 ROT barrel.

[Don McDowell]

Don, I’m still trying to shoot PP in my GM barrel 45-70 and am wondering who made your 45 dual diameter mold. Been thinking about this dual diameter thing vs breech seating. What are you using for a wad? And how critical is case length vs powder column height?

Mike , Brooks offers the original Sharps style dual diameter bullets. You can get them in either fixed base pour or nose pour adjustable.

I use the same Napa rubber cork wad and dry lubed felt wad as I do in all my patched loads.
I load them much like a greaser, seat it out to the lands for target shooting,or just short of the lands for just in case I want to eject an unfired case and not have to use a rod to get the bullet back out of the chamber.

[Distant Thunder]

There are basically three types of paper patched bullets.

The first step in choosing a paper patched bullet is to gather all the necessary information about your rifle to help you in choosing the best paper patched bullet for your rifle. I believe the fit of the bullet to your rifle is very important to accuracy with paper patched bullets. There are three basic types of ppb, bore diameter, groove diameter, and 2-diameter.

   

The first type of ppb is the bore diameter. When talking about bore diameter ppb I am referring to a straight, smooth sided bullet that when patched will be just a little snug on the tops of the lands when pushed through the barrel. This type of ppb is best seated out as far as possible, I seat my bore diameter bullets in the cases only .080-.100". This shallow seating puts a maximum amount of the bullet snuggly resting on the lands of the barrel, in perfect alignment. They can be extremely accurate for that reason. Also, they don't have to transition from the case into the lead and then into the rifling like a grease groove bullet does. They are probably best used in tight chambers where the case ID closely matches the patched bullet diameter. They can be made to work in grease groove chambers by neck sizing the cases to the best fit. Sizing cases down for every loading may require annealing the cases often. There are advantages to not having to go through all that.

Shallow seating is important with bore diameter bullets for one very important reason, it will help minimize the bumping up of the undersize bullet base to the diameter of your fired case when the powder ignites only to have it get squeezed back down to land and groove diameter as it moves into the barrel. This expansion and then down sizing of the bullet is not best for accuracy. This happens with any bullet that is seated into the case very far, but can cause problems especially with ppb and is best avoided.

   

The second type is the groove diameter ppb. These are patched to or slightly over the groove diameter. They can be loaded and shot just like grease groove bullets in rifles chambered for GG. Unless the rifle has a freebore, a straight unrifled cylindrical section immediately in front the chamber that is usually groove diameter or slightly over, these bullets can take up a bit powder space. This isn't a problem with the long cases like the .45-110 and may actually be desirable, but in a .45-70 a 540 grain groove diameter ppb can eat up much needed room for powder.

I designed a groove diameter pp bullet for my .50-70 just recently and it shoots very well, but that rifle has a freebore .350" long and the bullet isn't in the case too far. I can still load 75 grains of 2F with very little compression. That thread is on this forum if you are interested.

   

The next type is the bullet that brings together the best of both of the other designs, the 2-diameter ppb. It is the design that I want to explain in this thread. This bullet is perhaps the best suited to grease groove chambers and can be use in rifles with freebore to allow for a shallow seating depth like bore diameter ppb.

As the name implies these bullet have two straight sided sections of different diameters. The forward one is bore diameter when patched, the base section is groove diameter or .001-.002" over when patched. This larger base is made to be a much closer fit in the fire cases of a gg chamber and thereby eliminate the need for neck sizing and annealing for each loading. It can also reduce case growth and the resulting trimming of your cases so often.

With the 2-diameter ppb the length of the groove diameter base is designed so the seating depth is shallow like the bore diameter ppb putting most of the bullet up in the barrel for best alignment and increasing powder capacity. This gives a .45-70 almost the same powder capacity as a .45-90 and turns a .40-65 into a real .40-72!

I use a 2-diameter ppb in my .40-65 with 72.0 grains of 1 1/2 Swiss and only about 1/16" compression. It has proven to be very, very accurate and now handles the rams quite well thanks to the added velocity.

I happen to be just starting the design of a 2-diameter ppb for a .45-100 for another shooter. I plan to explain how I go about designing a 2-diameter ppb for a specific rifle so anyone interested in trying this design in their gg rifle can see the way I do it and what's involved. You should be able to follow the steps I use to gather the important information needed to have a ppb mold made that will give you the best chance of success.

DT

[Distant Thunder]

The rifle I am designing a 2-diameter paper patched bullet for is a Pedersoli Sharps that has been rechambered to .45-100. I don't have the rifle, which would be ideal, so I have to rely on the owner, Matt, for the information I'll need to get this done.

The things I need to know are, the bore diameter (.450"), the groove diameter (.458"), the mouth ID of a fire formed case (.460"), The bullets seating depth (.100"), The length of the throat (.125"+), and the amount the paper will add to the cast diameters (.007").

The bore and groove diameters I got from Matt. The case ID I measured from a case Matt supplied using a gage pin. For the bullet seating depth we agreed we would shoot (pun) for .100". The length of the throat (.125") I got from a chamber cast that Matt supplied. I would rather get this from the rifle by measuring to the base of a .459" diameter bullet resting against the lead angle, but I'll make do with what I have. The most that could go wrong is that the seating depth would be a little more or less, not the end of the world. For the amount the paper will add to the bullet diameter Matt sent me a patched bullet that he has been using in the rifle and I removed the patch and wrapped it around a .444" gage pin and measured the final diameter.

Matt said he has been shooting a .433" diameter BACO elliptical bullet and he has been trying to get it to shoot well for over two years. So we will see what happens with a 2-diameter bullet of my design.

When I say a bullet of my design please understand it's nothing special and I'm sure there are other bullets out there that are very similar. This design has shot very well for me in the long-range matches held at Lodi, WI. I have used this bore diameter bullet from a mold I made in 2009 to win 5 times and place in the top 5 13 other times. So the bullet does shoot well in both the rifles I've used it in over the past 9 years. The only difference will be that this new bullet will have a base diameter that will patch to groove plus .001" (.459").

When I used my bullet in my Shiloh .45-90 I had to taper crimp my cases quite a bit to hold the bullets in the cases. Using a 2-diameter version Matt will only need a very light taper crimp to hold the bullets in, if that.

In shooting a 2-diameter ppb in my .40-65 since last year I have come believe there may be an advantage to having a ppb that sets up against the lead angle when chambered. The accuracy that I'm getting from my .40 is amazing, the best I've had with ppb. I think having that little bit of initial resistance as the primer detonates and the powder ignites may be a good thing. I know that with my bore diameter bullet in my .45-70 just the primer alone is enough to move the bullet about 6 inches into the barrel. Don't ask how I know that, I just do.

The following a 3-D model of the proposed long-range ppb that Matt will be working with. It starts with an elliptical nose profile, but I modified it with a nose radius that is 28% of caliber because I don't believe overly pointed bullets are best in the transonic zone that we must work within when shooting BPCR. Most any load that can be safely fired with black powder will start out between 1200 and 1400 fps and all will drop below 1000 fps very quickly, usually within 400 yards. So it is with black powder and lead. I do like to keep the nose nearly half the overall length. This design has been very accurate for me and has proven to hold up well when things get twitchy and others are struggling to hold on to the target. I like this bullet! The overall length will be 1.440" which I find is very stable in an 18-twist rifle.

   

Now the real work begins!

DT

[AzTBH]

Jim

Thank you for starting this post on your design efforts of a 2-diameter bullet. I for one, with my limited paper-patch knowledge, very much appreciate that shooters like you and Arnie Seitz (aka beltfed) are graciously sharing your experiences and knowledge in your design efforts. In addition to the design aspects, your "There are basically three types of paper patched bullets” post was extremely helpful in helping me understand the differences between the three designs, their applications, and the advantages of the 2-diameter bullet.

The 3D model drawings in post #6 (.40 cal) and #7 (Matt’s .45 cal) were also helpful for me to visualize the bullet with a long freebore chamber (.40 cal bullet) and a no free-bore chamber (only a .125 throat) bullet for Matt’s rifle. A chamber cast of my 40-70SS indicates that the throat is only 0.050 in length, and no free-bore.

In addition to your technical expertise, I also enjoy your dry sense of humor. I almost sprayed my computer with a mouthful of Einstein Bagel coffee reading “Don't ask how I know that, I just do” comment following your statement "I know that with my bore diameter bullet in my .45-70 just the primer alone is enough to move the bullet about 6 inches into the barrel.”

I have a couple of questions:

1) Do you wet-wrap 2-diameter bullets? It seems that the wet paper would conform to the transition slope between the two diameters better than dry paper.

2) In the .45 caliber bullet drawing (Post #7) is the bullet patched to the dotted line in the center of the bullet (which looks like the start of the ogive)? Or does the paper go slightly higher (i.e. the first solid line to the right of the dotted line)?

Again, I do find this subject interesting and informative and will continue to follow the discussions. Please keep us updated on your experiences, Matt’s design, and other pertinent information on this subject.

Good Shooting,
Ross

[Distant Thunder]

Ross,

Thanks for your reply to this thread. I think a discussion on the 2-dimeter bullets will be very helpful to many who have heard the term, but may not know the particulars of the design and those who like to try them in a rifle that's not chambered for ppb. My hope is that this discussion will advance the use of paper patch bullets by more BPCR shooters. Some have tried the bore diameter version in their grease groove chambers and may not have had the best results or didn't like the case sizing that goes along with the undersize ppb. Other may have used the groove diameter version which usually works well, but are wanting more powder capacity. The 2-diameter design addresses these issues and more. So I wanted to get this information out to as many people as possible. This forum is a good place to do that without the negative replies from some that don't agree with this design. So here we are.

I hope to cut Matt's mold this week, but time is always the thing in short supply. I will post more information and pictures once I get the mold done.

Now to your questions.

"1) Do you wet-wrap 2-diameter bullets? It seems that the wet paper would conform to the transition slope between the two diameters better than dry paper."

I dry patch all my ppb and have for the past few years, but I share your concerns about the relatively short groove diameter section making it a bit harder to dry patch. On my .40 caliber 2-diameter bullet it's not a problem because the long freebore makes the groove diameter section is .525" long and the bore diameter part is only .150" long. When I dry patch these I just make sure I get the paper good and tight around the larger diameter and the rest is actually a bit loose up front. It might be just my chamber but I don't have any problems when chambering the cartridges and they shoot very well.

I believe Arnie dry wraps his 2-diameter bullets with their shorter groove diameter base and it takes a bit of practice but it can be done. It's just like wrapping a tapered bullet, which I have use, but it's a design that has never shot consistently for me. Although some have good results with them.

It you're not dry patching bore diameter bullets I would suggest wet patching a 2-diameter design just to make life easier. I'll know more once I have bullets from Matt's mold and start working on patch length and actually patching some.

"2) In the .45 caliber bullet drawing (Post #7) is the bullet patched to the dotted line in the center of the bullet (which looks like the start of the ogive)? Or does the paper go slightly higher (i.e. the first solid line to the right of the dotted line)?"

That patch to thing brings in a lot of variables. Some of it depends on ones own preferences and experiences, some of it depends on the particular rifle and chamber. I believe that bullet design may play a role as well as how much powder is being used. There maybe other factors that will determine what works best in a particular rifle.

I found out early on working with bore diameter bullets in my grease groove chambered Shiloh .45-90 that I got better accuracy when I patched to .020-.030" short of the ogive. I used the same bullet and patching when I transitioned to my .45-70 Hepburn with a special paper patched chamber. When I make a mold I like to cut it in such a way that there is a very slight step, about .001", at the start of the ogive. You can see the step in my current long range bullet in the first picture in post #6. That bullet actually has two lines and I patch to the lower one, the upper one is the start of the ogive. That design has been the most accurate long range design I have found. That is the design I will cut Matt's mold to and I will include a "patch to line".

I've got the roughing program made up for Matt's mold and the blocks are sitting on the machine. Now I just need a couple of hours to set up the blocks and run the first roughing cut. Then begins the very slow process of cutting the final size so that we end up with a bore diameter section that will patch as close to as possible to .450" with Matt's paper without going over .450". With bore diameter bullets I just size them after patching and all is good. With a 2-diameter bullet that isn't easy.

DT

[AzTBH]

Jim

Thanks for your detailed and informative reply.

It was surprising to me that that you and Arnie dry-wrap. Although the long freebore of the .40 caliber is a "perceived advantage" (my words) for your .40 caliber bullet, Arnie (albeit with a little practice) is also able to dry patch the shorter groove diameter base bullets. It was surprising because I visualized relatively loose paper on front of the bullet with dry wrapping. Which, is actually what you experienced, but it doesn’t seem to be a problem. I am not experienced enough to know for sure that wet-wrapping would be any tighter, but it seems that the wrap paper would follow the contour better than dry paper. It will be interesting to hear which technique works best for Matt.

I have never shot a paper-patch bullet, but I do have a bore-riding paper-patch mold that I purchased about ten years ago. My original intent was to give paper-patch a try, but it never happened. However, I did wet-wrap the sample bullets (.395 diameter) provided with the mold and they measure .400 with the Seth Cole paper. This discussion, along with others, has reinvigorated my interest in paper-patching and I am going to dry wrap to get a feel for the process. When I do shoot some bullets in my grease-groove chambered Shiloh .40-70SS, I will take your suggestion and patch .020-.030" short of the ogive.

I found your "very slight step, about .001”, at the start of the ogive” quite innovative. I am no bullet design expert, but I have never heard of this design feature before. Thanks for pointing out the “patch to line” step in the first picture in post #6. I can honestly say that I would have missed it without your explanation. Although different, it reminds me of the out-of-the-box thinking of Bryan Litz “Hybrid Ogive” bullet design (http://bulletin.accurateshooter.com/2011...-explains/).

I agree that this is the right forum for innovative design discussions and in your words "... a good place to do that without the negative replies from some that don't agree with this design.” Although the ODG experiences are great and we should draw upon it, I appreciate and applaud your and Arnie’s willingness to share innovative thinking of designing a 2-diameter paper-patch bullet for grease-groove chambered rifle. I also enjoy reading positive dialogs and thought-provoking questions that stimulate our collective learning.

Best of luck in your mold machining efforts and I hope your endeavors are a resounding success. I am looking forward to reading your next post with updates (and pictures) of Matt’s mold.

Ross