MikeT wrote:To get at least one groove near the base of the PP bullet; Just over-crimp with the taper crimp die. That should leave a mark on the bullet.
Not to get too far from the topic of grooves, bruce m says the highest bc is attained with a longer nosed bullet. Is it possible that
the two diameter bullet presents the "ultimate long nose" effect? First you will have a normal ogive, then a parallel section and last will be the full grove diameter. The bullet could be resembling a "cone" shape 'in-flight', with the point being the smallest cross-section and gradually increasing in diameter until the base of the bullet has the full grove diameter.
DT, will you and beltfed have a proto-type bullet at the Fall Lodi match?
Keep on hav'n fun!
MikeT
Naw Mike all it would do is cut a nice clean hole through the paper and nothing else
IMG_3256 (3).JPG
kurt,
do you mean cut the patch or the target?
keep safe,
bruce.
LOL Todd what else is there to do when you get up in age and cant hit the broadside of a barn anymore Yes Todd it was good to see you. I don't think I will make Lodi anymore it interferes with other shoots that run at the same time frame I like going to.
Kurt
The reason a dog has so many friends is because he wags his tail instead of his tongue.
"Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery"Winston Churchill
Bruce it cuts a clean hole through the target if it hits it
The reason a dog has so many friends is because he wags his tail instead of his tongue.
"Socialism is a philosophy of failure, the creed of ignorance, and the gospel of envy, its inherent virtue is the equal sharing of misery"Winston Churchill
Another thing about our Dual Diameter PP bullets is
since the Patch to FF case I.D./freebore/groove diameter
is "already there", one can use antimonial alloys since they do
not need to bump up to take the rifling. Presto, No ogive slump either.
My usual 9+1 ww/lino alloy is working well with the DDEPP bullets
I estimate the composition is: About: 94.5% lead/4.5% antimony/1% tin
beltfed/arnie
bpcr shooter,
that is the concept yes.
those bullets would be suited to freebore chambers of shooting long range, in order to get 1/8" to 1/10" just in the case.
in a no freebore chamber they woud suit hunting applications where more bullet in the case is an advantage.
arnie,
a good point well made.
that might be the reason i have come to love 12:1 alloy in my 40/72.
nontheless, my 12:1 bullet cut the paper right to the ogive, requiring them to be only a little shorter than 16:1.
they still bump up, as they did for the odg with conventional pp chambers and 1 diameter bullets.
keep safe,
bruce.
That is the idea and very close to what our 2-diameter bullets look like, but actual dimensions are very important. You need to know the dimensions of your chamber, your bore, and your paper as close as possible to get the two diameters and the lengths correct for best results.
I would not go with that nose shape if I didn't have to. This is just my opinion but I would go with an elliptical nose with a nose radius of about 30 to 40% of the caliber. I think that math works out? Arnie?
1) You need to know how much two wraps of your paper with add to your as cast diameters and it's not necessarily 4X. My .002" onion skin adds .007", at least that's the way I figure it.
2) You need to know your bore diameter, that is the diameter at the top of the lands. I measure mine with pin gauges.
3) You need to know the inside diameter of your fire formed cases and again I use pin gauges or my small hole gauge set. Hopefully this dimension is not more than .001-.002" over your groove diameter.
4) Then you need to know how far out of your case you can seat the case mouth I.D. (no. 3 above) -.001". This dimension plus about .090" will tell you how long to make the base diameter (the larger diameter) of your 2-diameter bullet.
The OAL of your bullet should be such that the twist rate of your rifle will keep it stable out to 1000 yards and beyond in just about any kind of wind. This, as we were saying earlier, may be somewhat determined by the nose shape you use. A longer more slender nose may require a faster twist or shorter length. If you go with the nose I suggested and assuming an 18-twist .45 caliber I would stay around 1.430" to 1.450" max, but that's just me and YMMV.
Following this as a guide you would end up with a bullet that is 1.430-1.450" OAL, with an elliptical nose ending in a .135" radius. The elliptical nose plus the .135" radius would be .700" to maybe .725" long (half the bullet length). The patch to groove diameter base (actually case mouth inside diameter minus .001") would be long enough to chamber up against the lead (rifling) and be .090" into the case mouth, + maybe .020" is ok. I think it is best for the transition between the groove diameter and the bore diameter to be an angle, like in your picture, and if possible it should match the lead angle. The patch to bore diameter section will just be the remaining length between the groove diameter base and the start of the ogive. The patched diameter of this should be as close to your bore diameter as you can get it without going over. Over would be bad because it gets complicated to size this part after patching. The groove diameter part is easy to size after patching, not so much the bore diameter.
I will add that I believe it is sometimes easier to get very good accuracy out of bullets that are a little more blunt than those that are pretty pointy. The down side to that is you end up having to come up more on your sights for a given distance with the blunter nose and you have to twist on the windage a bit more too. I like a good compromise between high BC and good accuracy, which is why I shoot the bullet I do.
Also please note that this is just my opinion and what has worked well for me in my rifles, and also a few others. This is certainly not the only way to design a dual-diameter paper patched bullet.
There are others on here that have done plenty of work with bullets of this type and I welcome their comments and suggestions. What do you say, bruce?
If I wasn't clear on something here please ask and I'll try to clarify.
DT,
i would say you have nailed the concept. better than i have been able to describe it.
how an individual uses that concept depends on their priority. e.g. hunting, long range, etc.
the angle of the diameter change would seem important.
just a question.
it s my belief that an ellipse is defined by a formula which includes x axis and y axis squared.
such an ogive does not have a radius, but is constantly changing.
one thing about these bullets as you say is the need to do accurate homework for full reward.
there exist those who will resist this aspect.
keep safe,
bruce.
Yes, I have cut my molds with an elliptical form defined by a major and minor axis, or a diameter and angle would work. Then I blend in a radius for the tip, usually about a .135" radius on a .45 caliber. That's in part why I don't call mine a prolate, that and it upsets Brent if I call it a prolate!
I like the long nose an elliptical profile gives me but I also want that bit larger hemispherical tip which I believe helps maintain stability at transonic velocity. I did this at first to help increase the weight, prolates are rather light for their length, but that design has done so well for me in some really twitchy winds that I have stayed with it in .45-70 for long range shooting.
My .40 caliber, which is a dual-diameter bullet, is not an elliptical profile. I gave up some BC to increase the weight for more knock down at the rams. It seems to work really well for silhouette and it shot very well out to 600 yards at Lodi back in May. Because I have that rifle scoped and there were only three of us shooting scope it kind of went unnoticed but I did shoot the highest aggregate score, out shooting the .45 caliber shooters too. If you saw my little 385 grain bullet you'd probably laugh at the thought of it performing as well as it does on paper targets at 600 yards. It is a good example of what you can end up with when you take the time to get all the dimensions right.
I like the dual diameter base section to be bore diameter to about .002 under bore diameter. I seat them much like you would a grease groove, using the "shoulder" at the base much the way the driving band on a greaser. Nose shape is a factor to a certain extent, altho those 44 and 45 bullets don't shoot enough difference in elevation than other more stream lined bullets to get worried about.
I think the most important thing especially with patched bullets is never mind the weight, keep the length to what the twist will fully stabilize in all the different wind conditions.
Width of the patch doesn't seem as critical to keeping elevation settings low with the dual diameter bullet as it does with a parallel sided "long pointed' bullets.
There's a zillion and three ways to skin a cat, the trick is to find that one that works for you And sometimes you can end up with a cabinet full of mould blocks, but only use a couple of them.
DT
my bullet is similar to yours in concept.
i wanted a pure ellipse, but the mould maker was not tooled to do the nose part so that is part of a hemisphere, 1/10" in diameter.
i wanted a nose 1.5 calibres long and still have that, as he went to the trouble to achieve it.
mine look somewat blunter than brent"s, but i am happy, particularly in light of this thread.
don,
you can't have too many moulds!
if you didn't try the others there would always be doubt that the one you are using is indeed your favourite.
keep safe,
bruce.
"...the most important thing especially with patched bullets is never mind the weight, keep the length to what the twist will fully stabilize..."
Don, you are so right here and it's an easy mistake to make and end up with a bullet just too long for your twist, Those can shoot well when condition aren't to bad, but throw a little wind shear at them and they bury themselves in the sand before making it all the way to the target!
That was one of the things I had trouble with when I first started with these long nosed bullets in my 18-twist .45s, I eventually learned to accept the somewhat lighter weight.
bruce,
We are shooting very similar bullets.
"you can't have too many moulds!" Apparently not, bruce, apparently not! I've got boxes full of them, I have no clue how many.
DT , it really is amazing how even a change of .06 in bullet length can completely wipe out unexpected dirt diggers.
But there's still the mystery of the money bullet that I haven't quite got figured out, and maybe don't need to, just do what the target says.... The BACO .446525 in a 16 twist 45-90 shoots fantastic out to 800, but starts to fall apart beyond that, but change nothing in the load except replace the bullet with the .446535 and that bullet stays together all the way to 1000.. But then to confuse the issue further, in the 19 twist Shiloh 44 barrels, if you take a ..435 diameter bullet at 1.35 it will shoot very well in mild conditions all the way to 1000, throw in a bit of squirrel winds in and things go to pot rather rapidly, shorten that bullet to 1.29 and presto you can go back to shooting with your big boy pants on, in any conditions..
So Im thinking when using twist calculators to determine bullet length one needs to forget about the caliber of the barrel, and use the caliber of the bullet.
