375/408 Banded Solids Test

[MontanaRifleman]

"Maybe you are including the bore rider in front... "...

Yes, I am. From an aero-ballistic standpoint there is no difference.

Ability to overcome wave-drag comes from ogive length (primarily), and ogive form (secondarily). There is no aerodynamic efficiency "credit" for a long projectile body, only potential "debits". Rifling engraving, engraving bands, pressure relief grooves, cannelures, etc. all contribute significantly to parasitic drag. You need to visualize a projectile shaft that has passed through rifling when estimating the drag penalty. At best, only smooth-surface drag will be present.

Mechanically, the bearing surface needs to be >1 1/2 calibers in length. Artillery shells typically have an ~2 caliber-long bearing surface. The practical requirements of mass on copper solids used in small arms is >2 calibers. The tail is between 1 caliber, and 1 1/2 calibers in length... as dictated by a boat-tail angle range between 7, and 9 degrees. The balance is left for nose length.

It is a balancing act.

I'm not so sure I agree that there is "no difference". The bore rider is .300 and the aft bearing surface is .307 That's the difference between a .284 and a .277 Not a lot, but something and it basically boils down to a more slender nose blending into the .300 rider vs a .307 bearing surface.

Anyway, in my experience, the more aggressive CEB BC's are descent for a copper bullet.

Do you have any ZA pics and dimensions?

 

[noel carlson]

"I'm not so sure I agree that there is "no difference". The bore rider is .300 and the aft bearing surface is .307 That's the difference between a .284 and a .277 Not a lot, but something and it basically boils down to a more slender nose blending into the .300 rider vs a .307 bearing surface."...

Montana, talk to me in calibers. For example, the ZA338 nose
is 1.19" long (3.52 calibers), and in a Von Karmann ogive.

 

[noel carlson]

//http://instagram.com/shlowlight

 

[MontanaRifleman]

I can't talk calibers with the CE bullets because I don't have that info. In any case their bullet doesn't fit the standard paradigm because of the bore rider. the front portion of their bullet is essentially a smaller caliber than the rear portion. whatever, it seems to work OK for them.

 

[noel carlson]

"In any case their bullet doesn't fit the standard paradigm because of the bore rider."...

This is simply not true.

"...the front portion of their bullet is essentially a smaller caliber than the rear portion."...

And the engraving depth is a different caliber than the non-deformed surface. It is a meaningless distinction. The nose is measured from the point, to the ogive junction with the "bore-rider" as you call it.

"...whatever, it seems to work OK for them."...

Without some point of reference, how is value assigned to this statement? If you do not know the basic dimensions, there is little to talk about in terms of the specificity you are asking for. I have examined the CE visually, and my statements are qualitatively accurate. If you want to get down to brass tacks, get your caliper out.

 

[noel carlson]

It dawned on me that you might not know how to convert bullet dimensions to calibers.

If a 30 caliber bullet has a nose 0.90" long, then:

.90/.30= 3 calibers

No manufacturer that I am aware of will make these conversions for you, but it helps immensely to visualize a projectile's aero properties if you think in these terms.

 

[Pdvdh]

Noel,
Are you selling bullets now? Been a few years since I was last reading about your ventures in bullet design and manufacture. PM me if that would be better for responding.

Paul

 

[noel carlson]

Hello Paul,

I think that it would be against forum rules to respond publicly.

Montana,

I found a good ISO-photograph of five CE 375's laid out in order of ascending weight:

- 325 gr.
- 350 gr.
- 375 gr.
- 400 gr.
- 425 gr.

They differ in only one dimension... the bearing surface (as I defined it).

The 325 grain had nice proportions generally, but tail length was less than one caliber. Photos, even when using a macro lens, can distort an image... but I am being generous in estimating the simple radius-ogive nose at ~2.7 calibers. That is not bad, but nothing to get excited about. It will generate significantly higher wave drag than the ZA375/6.4-M.

That is just a plain physical reality.

 

[Kiwi Greg]

Hello Paul,

I think that it would be against forum rules to respond publicly.

Montana,

I found a good ISO-photograph of five CE 375's laid out in order of ascending weight:

- 325 gr.
- 350 gr.
- 375 gr.
- 400 gr.
- 425 gr.

They differ in only one dimension... the bearing surface (as I defined it).

The 325 grain had nice proportions generally, but tail length was less than one caliber. Photos, even when using a macro lens, can distort an image... but I am being generous in estimating the simple radius-ogive nose at ~2.7 calibers. That is not bad, but nothing to get excited about. It will generate significantly higher wave drag than the ZA375/6.4-M.

That is just a plain physical reality.

By "bearing surface as you defined it" do you mean the bore rider?.

ie just in front of the seal tight band wear the rifling starts to cut the projectile.

Yes CEB are by their admission "conservative compared to some others" but they are relatively cheap, have very good accuracy & appear to have a better BC than anything else currently commercially available, so therefore IMHO are "something to get excited about"

Hopefully soon in the future we will have "better" projectiles to use but it appears at this moment anyway the CEB are at the top of the pile.

 

[noel carlson]

"By 'bearing surface as you defined it' do you mean the bore rider?."...

Yes.

"... so therefore IMHO are "something to get excited about"...

Under the present circumstances, that is understandable.

 

[noel carlson]

Greg,

How close is my estimate on the nose length?

 

[MontanaRifleman]

Hello Paul,

I think that it would be against forum rules to respond publicly.

Montana,

I found a good ISO-photograph of five CE 375's laid out in order of ascending weight:

- 325 gr.
- 350 gr.
- 375 gr.
- 400 gr.
- 425 gr.

They differ in only one dimension... the bearing surface (as I defined it).

The 325 grain had nice proportions generally, but tail length was less than one caliber. Photos, even when using a macro lens, can distort an image... but I am being generous in estimating the simple radius-ogive nose at ~2.7 calibers. That is not bad, but nothing to get excited about. It will generate significantly higher wave drag than the ZA375/6.4-M.

That is just a plain physical reality.

Noel, I'm not that familiar with the 375 projos. I have enjoyed Greg's videos and those 425's look very impressive, to me at least. I'm really in no position to judge which will have the least drag. I suppose shooting them head to head at the same velocity should settle the matter. Do you have any videos of your ZA line?

 

[Kiwi Greg]

Greg,

How close is my estimate on the nose length?

I don't have one handy at the moment to measure.

 

[noel carlson]

"I have enjoyed Greg's videos and those 425's look very impressive... "...

Yes, I have commented to Greg on the quality of his videos also.

"... shooting them head to head at the same velocity should settle the matter."...

With mass held constant, I agree.

"Do you have any videos of your ZA line?"...

Well, it appears time to produce some, and CE seems to be the benchmark.