New "to me" made in Montana monolithic bullets ...

[WildRose]

Bore Blast Benefits
Another effect of the cavity is something called "bore blast". There's a few different terms for it, but basically, as gasses are trying to escape around the bullet as it leaves the bore, the gasses are going faster than the bullet…that's why the bullet moves down the bore. The cavity helps disperse these gasses into a wider cone angle. So, when the bullet does leave the bore, it's not encountering as much turbulence.

That kind of makes sense to me. The conical base would be reflecting some of that blast energy to the rear like a shape charge which could I guess theoretically break up some of the trailing blast behind the bullet giving it a smoother transition from barrel to atmosphere.

 

[asd9055]

Extracted in part from AR Build Junkie an interview:

Q: I know there are other benefits to the Cavity Back design, can you talk about those?

Robert DeBell, Cavity Back Bullets: There's a couple of things that happen with a cavity in the back of the bullet. First, it increases the square area that the powder column pushes on, this helps the bullet get moving faster and mellows out the powder spike. So, in other words, you can push them farther than what you would typically be able to push other projectiles.

Center of Gravity/Center of Pressure
What we found is, in the technical aspect of it, is there are two things that affect flight of a bullet. One is the center of gravity, and the other is the center of pressure. As the bullet speeds up, the center of pressure moves back to the ogive, towards the back of the bullet. As the bullet slows down, the center of pressure moves forward on the ogive.

One of the reasons bullets have problems going through the trans-sonic zone, like the 168-grain Sierra…where a 170-something grain bullet doesn't, is because of the difference in the weight of the bullet between the center of gravity and the center of pressure. That particular bullet becomes unstable as it goes through the trans-sonic zone.

Shifted Center of Gravity
Because our bullet shifts the center of gravity toward the center of pressure but does not put it in front of the center of pressure, our bullets are more dynamically stable as they go through the trans-sonic zone. So, that's another thing we found. All, bullets when the leave the bore…they yaw. Our bullets tend to yaw less because the center of gravity is closer to the center of pressure than another other bullets. So, that's a side benefit when it comes to accuracy that we didn't even see coming.

Bore Blast Benefits
Another effect of the cavity is something called "bore blast". There's a few different terms for it, but basically, as gasses are trying to escape around the bullet as it leaves the bore, the gasses are going faster than the bullet…that's why the bullet moves down the bore. The cavity helps disperse these gasses into a wider cone angle. So, when the bullet does leave the bore, it's not encountering as much turbulence.

First, it increases the square area that the powder column pushes on, this helps the bullet get moving faster and mellows out the powder spike. So, in other words, you can push them farther than what you would typically be able to push other projectiles.

This statement needs further investigation. Though the area the pressure is acting on is larger as claimed, the forces are not all pushing forward! The forces are pepernticular to the poing they act, so take the hemisphere and draw them out. Sorry, the engineer in me could not leave this slide by

 

[WildRose]

First, it increases the square area that the powder column pushes on, this helps the bullet get moving faster and mellows out the powder spike. So, in other words, you can push them farther than what you would typically be able to push other projectiles.

This statement needs further investigation. Though the area the pressure is acting on is larger as claimed, the forces are not all pushing forward! The forces are pepernticular to the poing they act, so take the hemisphere and draw them out. Sorry, the engineer in me could not leave this slide by

This is true of course but then energy takes the path of least resistance.

It will be pushing out unidirectionally but it only has one direction it can actually go because only the bullet is moveable all all that energy ends up being redirected down the bore.

If not, the gun would simply blow up which is what happens if that bullet hits an obstruction before reaching the end of the bore.

 

[asd9055]

What I am saying is their statement is not correct!

 

[FEENIX]

What I am saying is their statement is not correct!

He expounded it in the following paragraphs.

 

[asd9055]

He expounded it in the following paragraphs.

Ed, I am not arguing about the remainder of the statements, just for the one I highlighted. And that is not covered in the rest of the statements. What I said it needs further investigation. I do not know ballistics, but I do know physics, pressures and forces.

 

[WildRose]

Ed, I am not arguing about the remainder of the statements, just for the one I highlighted. And that is not covered in the rest of the statements. What I said it needs further investigation. I do not know ballistics, but I do know physics, pressures and forces.

Then you realize that those expanding gasses are going down the barrel. They are limited by the bolt, chamber, brass and barrel and there's only one direction they can go which is out the end of the barrel.

They dumbed it down a little too much playing to the average audience is my guess.

 

[FEENIX]

Ed, I am not arguing about the remainder of the statements, just for the one I highlighted. And that is not covered in the rest of the statements. What I said it needs further investigation. I do not know ballistics, but I do know physics, pressures and forces.

I am not trying to argue, but he set the tone then tried to explain it.

 

[WildRose]

I am not trying to argue, but he set the tone then tried to explain it.

Well the conical shape may well act as they say at least in generating more velocity with lower pressures right before the bullet engages the lands.

Compared to a flat base or boat tail there's just a lot more surface area for the pressure of the expanding gases to act on.

I can think of several ways to test the hypothesis but not with the kind of equipment any of us have access to.

 

[asd9055]

Then you realize that those expanding gasses are going down the barrel. They are limited by the bolt, chamber, brass and barrel and there's only one direction they can go which is out the end of the barrel.

They dumbed it down a little too much playing to the average audience is my guess.

Not all forces are pushing forward! Some forces are pushing sideways against the barrel!

 

[asd9055]

I said all am going to say! Peace!

 

[cohunt]

What was the velocity claim vs. your actual velocity? Also, how far away to the lands are you loading them? Most of the information I have seen load them like the Barnes bullets and appears it likes a good jump, i.e., .050."

I went back and looked at my data from when i tried them a few years back ---2530-2550 for the cbb in a 16" AR was maxed out.
I can get almost 2700 from a 150 lead core ,2600 from a 150 barnes, I get 2490 from a 178 lead core-- have not tested hammers in this rifle yet though. I was running them at max cut out mag length for my ar-- so still quite a jump to the lands, as in an AR you can never really get close to lands with saami chambers

I could be wrong as I don't rember to well but i thik he was claiming about 100fps more than I was getting.

I'm not bashing the cbb, they may be a viable option for some, and others may see better results than myself. I just felt they weren't really all that different from other bullets. If you must use monolithic than they might be a good fit---- I would love to see a side by side with other monos ( barnes, gmx, hammer, cbb, maker, etc)

As I said earlier, I do like the 195mkz for 300bo pistol subs-- they are accurate in my gun

 

[FEENIX]

I went back and looked at my data from when i tried them a few years back ---2530-2550 for the cbb in a 16" AR was maxed out.
I can get almost 2700 from a 150 lead core ,2600 from a 150 barnes, I get 2490 from a 178 lead core-- have not tested hammers in this rifle yet though. I was running them at max cut out mag length for my ar-- so still quite a jump to the lands, as in an AR you can never really get close to lands with saami chambers

I could be wrong as I don't rember to well but i thik he was claiming about 100fps more than I was getting.

I'm not bashing the cbb, they may be a viable option for some, and others may see better results than myself. I just felt they weren't really all that different from other bullets. If you must use monolithic than they might be a good fit---- I would love to see a side by side with other monos ( barnes, gmx, hammer, cbb, maker, etc)

As I said earlier, I do like the 195mkz for 300bo pistol subs-- they are accurate in my gun

No Sir, I am not forced to use monos. Thanks!

 

[WildRose]

No Sir, I am not forced to use monos. Thanks!

Sooner rather than later if you hunt public land we're all going to be forced to do so. Hence I think it's wise to explore the options in the mono market so we can find something that will work for us before that day arrives.

Honestly I expect a lead ban on federal lands in the next three years as the greenies put even more pressure on the current administration and congress.