Designing the 2-diameter paper patch bullet.

[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