New Mould

[felix]

True about the land height. The big guns use micro-micro-lands(grooves). Thousands of them. They look like razor sharp triangles. ... felix

[carpetman]

Montana Charlie--You are waiting for the wind to quit ripping up your irrigation system. What should you be watching for? Leaks.

[montana_charlie]

Wind is still trying to relocate the county line, so no shooting today, but a quick (uneducated) word about CG.

Felix...We can alter the current design by using a fake lube groove in front of the groove riding section to move the CG foward some.

Bass Ackward...Personally, I think that the CG should always be to the rear because that is where it is easiest to stabilize.

If you take the various forces that are acting on a flying bullet and combine them into an averaged pressure point on the bullet, that is what they call the Center of Pressure (CP). Then, there is that balance point called the Center of Gravity (CG).

It's said by those who know that if the CG and the CP are at the same place on the bullet, it can't tumble - even if it has no spin. The round ball has this property.

On 'conicals', the CP is generally closer to the nose than the CG. The further apart they are, the more easily the bullet can be destabilized.

Knowing these two things (if not actually understanding all that they mean) makes me wonder if the absence of weight-reducing grease grooves in the rear, coupled with a somewhat slimmer nose, might cause the CP and CG on this bullet to be kinda far apart.

Rick and I did not set out to make a slim nose. The diagram from Dan Theodore had an impossible value for the ogive, so we (actually Rick) chose an ogive radius which made the smoothest transition from the .250" nose sphere to the .450" bore ride section.
It is only when comparing it by eye with pictures of other grooveless bullets Theodore uses that I see it as a 'slimmer' shape.

Here is an article by Theodore that mentions the CP/CG thing.
http://www.bpcr.net/site_docs-result..._Stability.htm

Here is another by him, which is what first (a year ago) got me interested in grooveless. The pictured bullet has a slightly 'fatter' nose than mine.
http://www.bpcr.net/site_docs-result...s_3G-45-90.htm

Oh, yeah! Felix,
To me there can't be any fake lube grooves. While this is a trial of grooveless bullets...if there was a groove, I could not stand to leave it empty...

CM

[omgb]

The velocity ceiling will be moot if BP is used. You're not going to go much faster than 1400 fps with a bullet over 200 grains.

Here's a funny point though I'm not too sure what it's worth. Hatcher, in his "Hatcher's Notes" discusses firing bullets straight up to see if they are lethal or not. He noticed during the testing that many spire-point bullets tended to land base first. this indicated that they were more stable falling base first. I'm not too sure how that enters into this discussion but, I found it interesting and thoght I'd like to share it.

[45 2.1]

If the boolit does indeed fly good, the easiest way to modify it would be to hollow point it with an adjustable depth pin. Hollow pointing a boolit usually increases the accuracy potential quite a bit.

[felix]

Very true, Bob. All BR bullets are hollow point types of some sort. ... felix

[montana_charlie]

Hatcher, in his "Hatcher's Notes" discusses firing bullets straight up to see if they are lethal or not.

I saw a segment of The Mythbusters where they tried to answer that question.
Based on penetration of spent slugs into the soil, they decided they weren't lethal...but they had a heck of a time FINDING bullets after shooting them straight up.
CM

[felix]

It's said by those who know that if the CG and the CP are at the same place on the bullet, it can't tumble - even if it has no spin. The round ball has this property.
... CM


True, it won't tumble, but it will dart, and that might even be worse! Now here is a salient fact: A true knuckle ball must have a very slight rotation, like one full rotation in 60 feet, to make the ball even more unpredictable at the plate. I don't think any of the present day pro teams have not one person who can deliver any kind of knuckler or forker with controlled rotation, either still or slight. ... felix

[45 2.1]

From the second article:
The Theodore/Brooks bullet dimensions are:
Length: 1.400"
Weight: 555 grains cast in 20-1
Ogive Radius: 4 calibers
Shank Length & Diameter: 0.400" & 0.4590"
Bore-riding Section Length & Diameter: 0.400" & 0.450"
Nose Length: 0.600"

Everything is OK, but he neglected to tell you the nose radius is about 0.168" which would make everything work as he said. He has 0.1" more bore ride/bearing than you do also.

[montana_charlie]

Speaking of velocity limit...RJ is right.
I'll be using BP, so I don't expect to get very far beyond 1200 fps.

For this first session, I only loaded 15 rounds because that is the number of new, annealed, cases I had on hand. I wasn't intending to shoot them over the Chrony...just fire for group at 100 and watch for leading and fouling problems, and fireform the cases in the process.

But the Chrony's available, so I'll add that to my plans...just for the additional data.

From the second article:
The Theodore/Brooks bullet dimensions are:

Yeah...I filed away that set of dimensions back when I first read the article, but that was a long time ago. I'm pretty sure he has modified the dimensions over time and testing, as the diagram he posted for me on the Shiloh forum is different.

Those numbers are:
Length: 1.450"
Weight: I'm getting 547 grains cast in 20-1
Nose Radius: .125"
Ogive Radius: 6.4 calibers (this was the 'impossible' number we changed to 4.733. He may have meant 4.6 calibers.)
Shank Length & Diameter: 0.400" & 0.460"
Bore-riding Section Length & Diameter: 0.300" & 0.450"
Nose Length: .750"

I assume his ongoing testing of the design made him come to settle on this shape, and the diameters are specific to the dimensions I gave Rick for my rifle.

I have the bullets thumb seated .3" into the case on a mildly compressed 85 grain charge with a .030" veggie wad. That makes for a very long OAL, but they chamber easily (with no fouling present).
My freebore is .1", and the exposed base band should be filling that completely. Basically all of the .300" bore ride should be laying snug in the lands. The bullet 'sticks' just enough to partially pull it, if I extract the cartridge without firing.

To me, this seems like a 'perfect fit'.
CM

[grumpy one]

I saw a segment of The Mythbusters where they tried to answer that question.
Based on penetration of spent slugs into the soil, they decided they weren't lethal...but they had a heck of a time FINDING bullets after shooting them straight up.
CM

I suggest being somewhat skeptical about that conclusion. I read an item in (I think, from memory) The Economist about three years ago regarding case reports of AK (7.62x39) military projectiles occasionally penetrating skulls slightly in Lebanon. Like several Arab cultures they have a tendency there toward vertical firing on festive occasions, even in urban areas, and once in a while someone gets hit. Occasionally that someone experiences a minor amount of penetration of the top of the skull - just the tip of the bullet, but nasty. The Mythbusters claimed that such cases must have been due to high-trajectory firing rather than true vertical firing. Personally I found the Mythbusters' methodology unconvincing, but the possibility of high-trajectory firing being the problem is also worth considering.

Geoff

[45 2.1]

Those numbers are:
Length: 1.450"
Weight: I'm getting 547 grains cast in 20-1
Nose Radius: .125"
Ogive Radius: 6.4 calibers (this was the 'impossible' number we changed to 4.733. He may have meant 4.6 calibers.)
Shank Length & Diameter: 0.400" & 0.460"
Bore-riding Section Length & Diameter: 0.300" & 0.450"
Nose Length: .750"
CM

CM-
Here is the 6.4 caliber ogive boolit. Nose radius is 0.1662". Should you want to try it, I could give you a detailed enough drawing to cut it with.

[montana_charlie]

CM-
Here is the 6.4 caliber ogive boolit. Nose radius is 0.1662". Should you want to try it, I could give you a detailed enough drawing to cut it with.

No, thanks, 45 2.1...at least for now. I want to stay with the .250" nose diameter (.125" radius), even though Dan's thread - where he explained the value of it - got deleted by a glitch on the Shiloh site. The (probably 4.6) ogive radius in his drawing was meant to go with that nose size.

In any case, I am much more interested in seeing what this bullet will do, than considering the next shape to be tried...and the shape you drew is pretty much the 'old' one from the previous generation, anyway.

If this one shoots accurately, displays the long range benefits that an improved BC is supposed to have, and doesn't cause barrel problems, I will stay with it.
If it doesn't perform at all - or it is bad for leading, I'll go back to the 'easy way' and use grooved bullets...leaving it to others to carry on with the search for grooveless perfection...'cuz I hate the thought of continually fighting lead.
If it leaves the barrel cleanly, but needs some 'adjustment'...then I would look at a different shape.


BTW, Rick made two moulds for me. The second casts a few ten-thousandths smaller in the two diameters, and it's vented a little more aggressively. At this time, I don't know which one I will keep, but I don't need both.
If any of you are interested having one for your own testing, let me know by PM.

If there are a number of guys interested I might put it up on our new little auction board...so everybody gets a crack at it.
But, that will be after I decide which one to keep.
CM

[SharpsShooter]

Sure hope the wind lays down soon. I am real interested as to how this turns out.

SS

[Red River Rick]

45 2.1-

That 6.4 ogive radius design would be interesting as well. If your offer for dimensional info applies to others, I'd be most greatful. I'd like to compare the dimesions of your design to the cavity I cut for MC.

I'd like to input your numbers and see how well they work out on the CAD program. Who know's, if things work out well mathematically, I may cut a cavity and some lucky person can do the range work.

RRR

[45 2.1]

45 2.1-

That 6.4 ogive radius design would be interesting as well. If your offer for dimensional info applies to others, I'd be most greatful. I'd like to compare the dimesions of your design to the cavity I cut for MC.

I'd like to input your numbers and see how well they work out on the CAD program. Who know's, if things work out well mathematically, I may cut a cavity and some lucky person can do the range work.

RRR

The nose dimension I gave is for a tangential ogive. The dimensions given by CM will not produce that, they will produce a definite break at the ogive/parallel part of the nose. You will have to decide which you want and give me your CAD parameters for your setup so I can dimension it correctly for you. PM me and we can discuss this.

[montana_charlie]

45 2.1,
Rick already has this drawing. I'm posting it just so you can see what 'square one' looked like for us...
CM

[martinibelgian]

Well,
MC isn't the only one active on the bullet front... This is my latest mould, but destined for PP:

Modern design? Absolutely not - just a faithful replica of the most succesful Brit LR match bullet in the late 1880's. See any similarities? Bearing surface is - of course - longer on this one, but that nose....
The bullet looks a bit messed up as it is the one that was shipped with the mould. Diameter .451, slight tapered section (0.150" long) between shank and nose to .441, nose 0.610" long. OAL is 1.5" for about 545grs in 20:1 alloy. Nose radius is 0.135".
Destined to be shot in following rifle, after rebarrel:

[montana_charlie]

See any similarities? Bearing surface is - of course - longer on this one, but that nose....

I see your nose as 'an encouraging word' which I hope to hear 'pronounced' tomorrow...winds are predicted to be 5 mph from the west.

I was under the impression that PP bullets were normally pure lead, but maybe that's because many guys like to make them by swaging.
I guess you'll depend on a grease cookie to manage BP fouling, and the patch will prevent leading...right?

I have to depend on the dip lube for both, and it's a bit of a hassle, but I think I can dip 'em faster that you can put those diapers on...just hoping it is as effective.
CM

[martinibelgian]

Charlie,
There are 2 kinds of PP bullets - 1 theory is to have the patched bullet at land diameter, use pure lead, and rely on bump-up.
Not with this one - the naked bullet is groove diameter, and it is patched up to groove diameter, so I can use a harder alloy, no bump-up needed. And yes, I'll depend on a lube wad for fouling - I will try paraffine-soaked felt wads, as they were also used back then. I will also try no wad, and wiping between shots though. Shouldn't be a problem. Of course, this bullet will be shot in a period-correct cartridge - 500/450 #2 Musket, which was the Westley Richards LR BP match round of those days.
This one is about rediscovering things whch were generally known back then, but have disappeared from use since.
Mind you, I could also use it naked and-dip-lubed in my ML rifle