A fella and I were chatting yesterday about the methods to beat the wind problems... I thought I'd see what others think.

ALL THINGS BEING EQUAL (BC, distance, environmentals, etc) I believe that if I push a bullet faster I am less effected by wind. If I elect to use bullets from different manufacturers and these bullets have the same BC .507 but I can push one (1) of these 100 fps or more faster than the other it's a no-brainer to use the faster bullet as I gain a trajectory edge as well as a windage edge...

Is this sound thinking (theoretically)??

Your thoughts.

"I spend half my money on guns and bullets... and I waste the rest.


Note to Admin: I'd have posted this in the How To: section but I don't have new post rights there.

You clearly gain a flight time advantage, which can only help with wind drift.

But something I've been thinking about lately is the concept of gyroscopic stability. Usually when we talk about the bullet being a gyro, we say "it's stable" or "it's not".

But what I'm wondering is, if the projectile is spun faster, does it resist external forces any better? Whether because it doesn't yaw as much, or for as long a time, lessening rear drag, or whatever - is there benefit with regard to wind effects if you spin the thing faster?

In your case, you're getting more RPM with the faster bullet - does it help any? Food for thought...

Dave....Sorry about the How to, I just have not got around to creating all the moderator groups, I will fix this one today. This is a great topic.

Truth and Objectivity are Mutually Inclusive

[b]ALL THINGS BEING EQUAL (BC, distance, environmentals, etc) I believe that if I push a bullet faster I am less effected by wind. If I elect to use bullets from different manufacturers and these bullets have the same BC .507 but I can push one (1) of these 100 fps or more faster than the other it's a no-brainer to use the faster bullet as I gain a trajectory edge as well as a windage edge...[/b]

Dave,

I'm thinking that is fact, not theory?

On that note:
I've found my dad and I both can shoot the 178 A-Max a bit faster than the other 180's we've tried, and the BC's are vitually the same. It's worked in three rifles anyway. 50-100 fps gain at the same pressure.


PR,

[b]But what I'm wondering is, if the projectile is spun faster, does it resist external forces any better? Whether because it doesn't yaw as much, or for as long a time, lessening rear drag, or whatever - is there benefit with regard to wind effects if you spin the thing faster?[/b]


Using the same bullet weight, but spinning it faster I'm guessing?

Isn't there more drag "after" the bullet reaches max ordinate from "overspinning" it, as its axis won't follow the tangent of its trajectory, but hold a nose high attitude increasing air drag and lowering downrange BC?

Considering RPM decay is much less than velocity, I'm guessing a higher BC bullet will do better at reducing this nose high position because the rate of velocity decay to RPM ratio does not change so rapidly?

Brent,

Yep, I'm talking about a) either running the bullet faster, or b) increasing the twist rate of the barrel.

I understand your point about overspinning - I know why that's a bad thing for rear drag. I'm talking about what is probably a large range of RPMs that consititute a "not overspun, but gyroscopically stable bullet". My question is, is a bullet that is spun to the top of that range (just under whatever value causes the overspin condition) more resistant to external forces and rear drag than one that is not spun so?

PR,

That's what I was thinking you were meaning, now I wish I had the answer. ha,ha
Any ideas of why it would?

PaleRider & Brent

Aren't there a "nearly" fixed "n" set/amount of forces/effects for the flight of a projectile (external ballistics) and aren't these interrelated? If we increase the velocity and the mechanically linked rpm's we have less TOF but perhaps we then suffer a corresponding increase in Magnus Force and overturning moment (and other things things I don't understand)?


Magnus Force
http://www.rmcs.cranfield.ac.uk/aeroxtra/exb4mpmm3.htm


Overturning Moment

http://www.rmcs.cranfield.ac.uk/aeroxtra/exb3c.htm


This is the type of stuff I enjoy about these boards...free education.

"I spend half my money on guns and bullets... and I waste the rest.

I think in practical terms, the faster you shoot a bullet the more Rpm is needed to keep it stable. The good news is, the faster you shoot a bullet in the same barrel, the more rpm you do achieve. Having worked a few of these formulas out a few years ago, I seem to remember that the gyroscopic stability factor goes up only slightly as you shoot through the same twist rate at higher and higher velocities. No where near approaching the percent increase in actual RPM.

PR and I have talked about this several times, and I suspect that by spinning a bullet way faster than you need to could pay off with significantly less wind drift, provided you were capable of moving the CP and CG much closer together with a high density core, and an aggressive secant ogive.

Truth and Objectivity are Mutually Inclusive

"Wind" seems to be used pretty generically here.

In a left to right wind (and always assuming a right-twisted bbl) a faster bullet probably does marginally more harm than good. Decreased flight time, yes but also more forces that the wind can use to it's advantage. On the otherhand a right to left wind should be marginally better with a faster bullet. Just my own thoughts. I don't have the math background to prove any of it. -Rod-

*******************************
Handloading is a means to an end, but the end never seems to stay still -ME
***********

USAPatriot

Let's chat more about this... You gave me a nice bone but not too much meat on it. I could dig more on my own but a few more bits of info would be greatly appreciated...

/r

[b][i]"I spend half my money on guns and bullets... and I waste the rest."[/i][/b]

How does the aggresive secant move the CP and CG closer together with the use of denser core material? I don't have a good understanding of CP throughout the trajectory, and how it relates to CG.

The bones are here, same with you USA, now throw us some meat... Ok, please.

Center of Pressure is not an easy thing to visualize dynamically. But if you can imagine a cone pushing through a fluid (or Gas), the first millimeter of the tip of the cone has less surface area (small diameter), than the last millimeter near the major diameter of the bullet. So as this cone displaces your gas or fluid by moving through it, you might imagine that there is more pressure on the larger diameter of the cone than there is near the tip. Now it is more complicated than this because with bullet flight you have supersonic shock waves at the tip and also where the ogive meets the major diameter. The fact is a number of these things must be averaged to get a reasonable estimate for the center of pressure. If you can visualize the different shapes that a secant and tangent ogive have, then it becomes easier to visualize why an aggressive secant ogive would cause a greater percentage of the pressure for moving or displacing a gas a little more rearward on the physical body of the bullet jacket.

Truth and Objectivity are Mutually Inclusive

Brent/David,

My brain sees it as an aerodynamic effect, much like a sailboat tacking into the wind. A bullet rotating against the wind should have pressure variances that 'might' give it wind-bucking properties, like the boat. The opposite would be true of a bullet rotating in the same direction as the wind. I don't know of any way to practically test the idea though. -Rod-

*******************************
Handloading is a means to an end, but the end never seems to stay still -ME
***********

USAP,
I don't see how a bullet rotates only against, or the same direction as the wind?

Top rotates into the wind, but at the same time, the bottom rotates with the wind, or vice verse?

I think the drag created on the bullet at different angles, with reguard to rotational drag, creates low pressure areas around the bullet and the bullet naturally moves away from the high pressure into them, am I all washed up?

This can mean vertical drift change, with respect to wind direction and rotational direction, as well as horizontal drift.

.....

Ok, starting to make more sense now.
Using denser cores in the same cavity -
Wouldn't this shift the CG even more to the rear than the lead core, unless the fore and aft CG happened to be dead center of the cavity, assuming the cavity it flat front and rear.
Now if the cavity tapered into the nose, like match bullets, this moves the CG forward. Change to a denser core and it moved rearward though? Wouldn't the cavity need to be moved forward to compensate for the aft CG shift caused by a denser core? Higher density cores could let you retain the core weight, but reduce the cavity at the rear tho, you still could end up with a shift forward in CG with keping the same weight, maybe a bit more weight even?

Assuming it would be desirable for the CP and CG to be at the same point on the bullet, how does it help wind drift? And wouldn't higher RPM add to vertical drift tho?

No, you're not all washed up. Low pressure/high pressure should be exactly right. With spin drift and the bullet wanting to move into the wind from an aerodynamic standpoint is the idea. In practical terms it boils down to the question "at what point does wind velocity overcome the ability of a bullet to tack into the wind?" It seems to me that at some point, dependant on the angle and velocity of the wind as well as the bullet (and it's spin rate), there's going to be an equilibrium. Some of you math wizards could probably explain it mathematically. I can only visualize. -Rod-

*******************************
Handloading is a means to an end, but the end never seems to stay still -ME
***********

Keep in mind that you have boundary layers, and that the rear drag imbalance component represents over 70 percent of the deflection component.

Truth and Objectivity are Mutually Inclusive

Brent,

"Using denser cores in the same cavity -
Wouldn't this shift the CG even more to the rear than the lead core, unless the fore and aft CG happened to be dead center of the cavity, assuming the cavity it flat front and rear."


It is true, that when you go to a denser core, and keep bullet weight the same, it does shift the cg rearward. However, when you build on denser cores, you go to a much shorter jacket, and the whole ogive shifts rearward at almost twice the rate the cg moves.

Truth and Objectivity are Mutually Inclusive

Or, you could use two different materials for the bullet core, the denser one in the front part to try to match the CG with the center of pressure. This is suggested by Corbin (they sell powdered tungsten for the people who want to experiment), but I guess one thing is theory and quite another an impeccable execution of the idea.

To me, in theory spinning a bullet faster than needed will help with things like wind, it does for a fact help terminal ballistics and it also generates slightly more energy.

What I have found in my own research is that every time I shoot a load that is spinning much too fast than what is needed, it ends up never reaching 1k. Also sierra has done studdies to show that over stabilizing a bullet decreases the overall BC. For the most optimum BC, twists are used in proportion to the bullets being used. Higher BC's = less drift.

Just my.02

Michael

Its not about how many rifle you have, its about how well you can use what you do have.

I have fired 9 inch three shot groups at 1760 yards with a 1 in 9 300 WSM shooting a 200 gr. PRL that will easily stabilize in a 1 in 12. There are a lot of MYTHS out there.

Truth and Objectivity are Mutually Inclusive