Designing the 2-diameter paper patch bullet.

[Don McDowell]

Jim this is a fascinating journey. Thanks for bringing us along.

[Kurt]

Jim the cavity sure looks good. Did you make a D cutter and what do you use to grind it?

[Distant Thunder]

Kurt,

I cut these paper patch molds in my vertical machining center and use just standard endmills. I use my CAD/CAM software to create a 3-D model of the bullet, form that I make a 3-D model of the mold blocks and use that to generate the code for the machine to cut the cavity. The process works pretty well and allows cutting just about any nose profile without special tooling. Grease groove bullets do require special cutters and I have made many of those kind of cutters.

[Distant Thunder]

Don,

I am happy to have a place to make this information available to all interested. I am glad to see that there is a good amount of interest in paper patch and the 2-diameter version especially. I think if these 2-diameter bullets are designed and used properly a lot more shooters will have success shooting paper patch bullets. Paper patching is a fascinating part of the history of black powder cartridge and we really need more shooters using them. They are superior to GG in many ways, but especially in the coolness factor! No one can argue that point.

[Distant Thunder]

Today I was able to cast about 40 bullets with this new mold and I am pretty happy with the way it casts and the bullets I made with it. The diameters are good, but the bore diameter portion is closer to .449" than the .450" I wanted. I think we'll try it there first and see how it chambers and shoots before I panic. One problem with the 2-diameter design is that sizing an over size bullet is much more complicated than with straight sided bore diameter or groove diameter bullets. Looking at that thought .449+ is not necessarily a bad thing. The groove diameter came out right at .459" and fits the case really well. Matt will have to load and try these to see if they fit his rifle(s). If he can load these so that the groove diameter base seats tight against the rifling I believe they will shoot very well.

I should give these a try in my C. Sharps .45-70 though I may have to virtually breech seat these with my freebore in that rifle. That would still tell me a lot but it is not practical for competition with any time limits.

The mold itself casts very well, it fills out easy and fast so that even the first bullets were sharp and crisp. I did have to put two spring washers on the sprue plate or it will too quickly flash at the base and that is a PITA. They weight between 521 and 522 grains, which is right where I wanted them to be based on my straight sided bore diameter bullet of the same profile. They are pretty close to round, +/- .0005". The OAL is 1.435", perfect for an 18-twist.

Here is a look at the bullet sitting in one of Matt's .45-100 cases. I patched it with a sample patch that Matt sent me and it is not quite what I would recommend he use, but we'll address that when he starts loading these. It does show me what he'll get for diameters using his paper. I will check it with my paper too so I'll know what to shoot for on when I cut my mold hopefully not too far down the road.

   

[Kurt]

TNX. Jim.

I really like the ogive on that bullet it's very close to a prolate as you can get. I was wondering on the fine boring job how you ground the bit. I used a drill rod softened it and did a lot of grinding and filing and stoned the final edge with an Arkansas after re tempering the rod. A lot of work for a retired plumber LOL.

A Duel diameter bullet definitely has a place shot in a standard GG chamber, saves the brass and they work. I had a Corbin swage die made for the .50 that was a 2 diameter tat patched the base to groove and it shot very good in the .50-90 but When I ordered the Die from Dave he warned me not to use to hard of an alloy or you will blow off the base and he was right, 1/16 with his dies in .50 calibers for the S press is to large. But they shot very good.
I also have a press and dies from Richard Corbin and those dies use a 7/8X14 thread and this makes the die a lot stronger and I always thought I would have Richard make a two diameter die but anymore with the custom mould makers we have now days I can cast a bullet just as good as a swaged for a lot less cost. When I started swaging the bullets I wanted to use the moulds were not available.

[Don McDowell]

I'll bet if the length of that patch had less of a gap between the ends, that bullet will shoot lights out.

[Distant Thunder]

I also want to add that I don't cut my patches for these 2-diameter any different than those for my straight sided bullets, but I do start the patch a little differently on the bullet, at a very slight angle. With a little practice 2-diameter bullets wrap just as easily and the straight sided bullets do. I dry patch all my bullets so if you intend to wet patch your 2-diameter bullets things my be different, I can't say for sure.

I do believe it would be worth your time to learn to dry patch, for me it has made a noticeable difference down range. As with everything I do and suggest YMMV. In the end you have to do what works best for you in your rifle, I only know what has worked best for me in my rifles.

[J.B.]

You make it look easy Jim . I've got a ways to go with my experiments with dual diameter but it certainly appears to be the way around shooting pp in grease groove chambers if one wants to go easy on working the brass. I'm really keen to try my Brooks d/d in my 1/17" twist 44 but that will have to wait to later in the year as that rifle lies dormant in the U.S. until June . In my 1/19" it seems to do well to about 500 yds and then all bets are off. I gather this is the length vs twist issue so I'll shorten it up a little for my next test. One thing that I did find with patching is that a Ballard 45 template I had is almost perfect for the d/d 44 bullets. Ideally the length at the top of the patch needs to be reduced but the difference is minimal. As always... an interesting thread. Happy New Year to all.
rgds.. Gavin.
ps. perhaps I'll try patching on a the slightest angle and see if the problem is lessened.

[Kurt]

Jim that bullet is pretty close to my .40 on the far right. I hope yours shoots as well as mine.
My chamber is to tight for a duel diameter it won't fit the fired case mouth. My bore diameter just fit the case mouth and I can turn it upside down and it won't fall out seated in a unsized case.
I don't wet patch, I just don't get the accuracy as dry and I found paper on the target backer at 200 yards wet patching.