daul diameter ppb's & the 40 2-5/8" bottleneck
Posted: Tue Nov 20, 2018 5:16 pm
Over the past year or so, I have made a big push to shoot paper patched bullets competitively in silhouette matches. So much of a push that patched bullets have been almost an exclusive diet to all my rifles. Shooting in the same class as I and routinely besting me with every outing is my wife who still shoots the greasers with a blow-tube. It has been (and still is) a learning curve for me. Probably always will be learning something new with every outing. It has been frustrating at times, embarrassing at times, and successful on more recent experiments. At the start of this paper patching endeavor; I started with cartridges that were long discussed about as being patched for to better self-educate as to what was working, what wasn’t, and why the outcomes yielded such. Using this forum and talking with much more experience shooters; I kept at it. Keeping my pride tucked when milestones were hit and being stubborn enough to keep going when failures were endured until my more favorable attempts could be duplicated. For the most part, paper patching is a rather straight forward and surprisingly easy thing to do successfully; that is so long as you listen to those who have mastered it. Get a bullet that when properly wrapped, fit’s the bore like a glove. Fouling control and wiping routine must be consistent every time. Then its all comes down to the skills as a rifleman.
In my more recent “B series” Shiloh’s the chambers are very exact with almost zero throat to them allowing a shallow seated straight sided bullet to shoot accurately down range. I have two older Shiloh’s from the 80’s that bare the stamps of when Shiloh and C Sharps were one in the same. One a 40 1-11/16” bottleneck. The other a 40 2-5/8” bottleneck. I never fully understood the problem of the long throat that I’ve continually read about. I’ve always shot greasers through these rifles and adjusted the OAL so that the first driving band was up against the lands. Pretty basic and straight forward process to get favorable results. I found it much more puzzling when I shifted my efforts of patching the newer 45 calibers to these bottlenecks. No matter what style of bullet I want to shot, I always do a chamber cast to measure and see in a 3D representation of exactly what I’m dealing with. So from the start, I knew these two rifles had about .200” of free-bore. Yet I still tried what had previously worked for me in the 45 2-1/10” and 45 2-6/10”. no matter what I tried with wad materials, compression, alloy temper, and fouling control; I just could not get competitive accuracy. I started thinking that perhaps the internet myth about bottlenecks was true- “they don’t shoot well, they foul out, and are mild mannered at best.” Then I thought about how well and how easy it was to get my grease grooved bullets to shoot. I was genuinely puzzled at what I was or wasn’t doing right. Yes attention to fouling control has always been more important with these two cartridges but from the start, these two guns would shoot fairly well with greasers. Every time I went down range to analyze paper, wads, bullet holes and the bullets themselves (if I could recover them); I kept my fingers crossed to see if things would ever start to show promise.  After a few days of chewing over very complicated experiments and elaborate ways to change things in my loads, it occurred to me that I failed to account for the most basic of all my practices. That was to make the bullets fit the rifle. My brass fit, I measured the bore and found a bullet/ paper combination to fit, my loaded cartridges chambered smooth every time, BUT I never took the .200” free-bore into consideration. I felt like a big rookie! Immediately it all made sense. Everything from how the bullet bases looked after firing, the blow-by on the paper shreds, uncalled flyers; it was all because my bullets were being blow out and then reduced down again upon every firing. So it was back to basics. I got on the forum and did my homework with something I remember distantthunder and beltfedarnie discussing and that was dual diameter bullet profiles. I knew this fairly new concept couldn’t be any worse that what I had already tried so I decide to jump in. I redid my chamber casts of both rifles and to the best of my ability; I measured everything. The length of the throat, the diameter, even tried to get a good read of the transition angle from throat to land. From there I began to draw up a bullet design that when #9 paper was applied, would fit the chamber, throat, and twist rate like a glove.
I first acquired a few tapered bullets from a fellow member of the forum to test the theory behind my bullet. These test bullets had a .393” nose section that tapered up to a .395” base. That .395” cylinderncontinued to the base for about .250”. Their performance was much better than any of my attempts with a straight sided profile yet the rifles still struggled to be competitive. After testing that design, I sent my design to Tom at Accurate Molds LLC to be cut. I made the OAL 1.21” to fit the 1-18” twist of both these rifles. Using #9 onion skin paper, I made the nose diameter .393” for my .400” bore. The base diameter is .403” to fit my .410” throat and is .28” long. My throat is .200” long so this gave me .080” of seating depth into the case. When the mold arrived in the mail, I tore into it like a kid on Christmas morning and started casting that evening. Using my 25:1 alloy the bullets come out at 369.7 grains. 
In my more recent “B series” Shiloh’s the chambers are very exact with almost zero throat to them allowing a shallow seated straight sided bullet to shoot accurately down range. I have two older Shiloh’s from the 80’s that bare the stamps of when Shiloh and C Sharps were one in the same. One a 40 1-11/16” bottleneck. The other a 40 2-5/8” bottleneck. I never fully understood the problem of the long throat that I’ve continually read about. I’ve always shot greasers through these rifles and adjusted the OAL so that the first driving band was up against the lands. Pretty basic and straight forward process to get favorable results. I found it much more puzzling when I shifted my efforts of patching the newer 45 calibers to these bottlenecks. No matter what style of bullet I want to shot, I always do a chamber cast to measure and see in a 3D representation of exactly what I’m dealing with. So from the start, I knew these two rifles had about .200” of free-bore. Yet I still tried what had previously worked for me in the 45 2-1/10” and 45 2-6/10”. no matter what I tried with wad materials, compression, alloy temper, and fouling control; I just could not get competitive accuracy. I started thinking that perhaps the internet myth about bottlenecks was true- “they don’t shoot well, they foul out, and are mild mannered at best.” Then I thought about how well and how easy it was to get my grease grooved bullets to shoot. I was genuinely puzzled at what I was or wasn’t doing right. Yes attention to fouling control has always been more important with these two cartridges but from the start, these two guns would shoot fairly well with greasers. Every time I went down range to analyze paper, wads, bullet holes and the bullets themselves (if I could recover them); I kept my fingers crossed to see if things would ever start to show promise.  After a few days of chewing over very complicated experiments and elaborate ways to change things in my loads, it occurred to me that I failed to account for the most basic of all my practices. That was to make the bullets fit the rifle. My brass fit, I measured the bore and found a bullet/ paper combination to fit, my loaded cartridges chambered smooth every time, BUT I never took the .200” free-bore into consideration. I felt like a big rookie! Immediately it all made sense. Everything from how the bullet bases looked after firing, the blow-by on the paper shreds, uncalled flyers; it was all because my bullets were being blow out and then reduced down again upon every firing. So it was back to basics. I got on the forum and did my homework with something I remember distantthunder and beltfedarnie discussing and that was dual diameter bullet profiles. I knew this fairly new concept couldn’t be any worse that what I had already tried so I decide to jump in. I redid my chamber casts of both rifles and to the best of my ability; I measured everything. The length of the throat, the diameter, even tried to get a good read of the transition angle from throat to land. From there I began to draw up a bullet design that when #9 paper was applied, would fit the chamber, throat, and twist rate like a glove.
I first acquired a few tapered bullets from a fellow member of the forum to test the theory behind my bullet. These test bullets had a .393” nose section that tapered up to a .395” base. That .395” cylinderncontinued to the base for about .250”. Their performance was much better than any of my attempts with a straight sided profile yet the rifles still struggled to be competitive. After testing that design, I sent my design to Tom at Accurate Molds LLC to be cut. I made the OAL 1.21” to fit the 1-18” twist of both these rifles. Using #9 onion skin paper, I made the nose diameter .393” for my .400” bore. The base diameter is .403” to fit my .410” throat and is .28” long. My throat is .200” long so this gave me .080” of seating depth into the case. When the mold arrived in the mail, I tore into it like a kid on Christmas morning and started casting that evening. Using my 25:1 alloy the bullets come out at 369.7 grains.