Ball Flight

[rodwha]

On another forum a fellow there claims that the numbers a ballistics calculator gives doesn't jive with what's seen in the field.

I've used this formula to find the BC of a .490" RB, and the Hodgdon's load data for an approximate velocity to get an idea of what the trajectory and wind drift would be.

B.C. = Ball Wt. in grains divided by (10640 x ball dia. x ball dia.)

Example: For a .535 ball weighing 230 grains, 230 divided by (10640 x .535 x .535) = a BC of .0755. Lyman's Black Powder Handbook gives a BC of .075 for a .535 in. ball, so the agreement is good. This formula courtesy of "Lee in Denver"

But this fellow claims those numbers aren't even close to accurate.

Hodgdons states an 80 grn charge of RS would give 1701 fps, and I came up with 0.069 BC for a 177 grn .490" RB.

According to a ballistics calculator were I to zero the ball at 100 yds I'd be about 2.5" high at 50 yds and 4.2" low at 125 yds (700 ft elevation). But at 100 yds I'd have 10.6" of wind drift with a 10 mph crosswind. Assuming I have a velocity of 1700 fps can I not trust these numbers to be close enough?

Do any of you guys notice much different field experience than what a calculator would give you?

 

On another forum a fellow there claims that the numbers a ballistics calculator gives doesn't jive with what's seen in the field.

{GUN GEEK ALERT} :rotf:

Work up the load that is the most accurate for a given gun. Why would anyone care what a ballistics calculator says if you're hitting your mark? It's just one more thing for guys to argue over. IMO

 

[necchi]

Yes.
There are variables in the load it`self that lend each shooter being different even if they use the exact load listed in a chart.
Unless you personally shoot your load over a chrony the book stat's aren't even close.

Example, If I zero at 50 with a 490 .020 patch and 80grns of "powder"(in and of itself a variable) I'm about 5"s low at 100.
How does that calculate for ya?

 

[TFoley]

My ballistic calculator was made in the great Bluegrass state of Kentucky.

tac

 

[George T.]

I have been shooting rifles since 1951 and I own all types of rifles as well as MLR's. The charts , tables and formulas get you in the ball park barring a large delta in velocity. It is necessary to verify these numbers in the real world though. Will the difference cause a miss on a big game animal? Probably not however it could result in a marginal hit.

Geo. T.

 

[rodwha]

I can only technically test any given load at 50 and 100 yds. A calculator could give me an idea of what to expect just a little further. Or it could help me if I were to want to zero it in at 75 yds (which I've been considering as optimal). I could then figure where it ought to be at 50 or 100 yds and work it out.

But more importantly to me would be the wind drift.

I don't need it to be exact, but if I know that it ought to be close then I'm good. Without a chronograph I wouldn't even know if my velocities match.

 

[nkbj]

Any yall ever seen imparted windage at distance, like a curve ball.

 

[silly goose]

If I knew there was gonna be math, I'd have never gotten into this stuff. :grin:

 

[Billnpatti]

There are just too many factors involved for a reasonably priced ballistics calculator to give you spot on results. There are military grade ballistics calculators that are spot on but they are not inexpensive. We are talking several thousand dollars for one. Most of the ballistics calculators that are available online are pretty close but will not give you absolute dead on real world results. It is a lot like bore sighting.

 

[necchi]

If I knew there was gonna be math, I'd have never gotten into this stuff. :grin:

:rotf:
Yeah Man! Just ask anyone here about my math!!
It's been real world shooting for me to figure this round ball ML shooting game right from the get go.

And yes, GoodCheer, I have seen ball being pushed by the wind and have learned to adjust for it.

(Not seen-seen like you do a curveball on TV, but the results at the target)
More like, :hmm: Hmm, the winds blowing left to right, better hold it to the side a bit.

 

[nkbj]

Meant like a curve ball, caused by rotation creating unequal pressures.
(No rifling acts like a knuckle ball.)

 

[necchi]

:redface:
Oh, then Nope.

 

[54ball]

{GUN GEEK ALERT}

Work up the load that is the most accurate for a given gun. Why would anyone care what a ballistics calculator says if you're hitting your mark? It's just one more thing for guys to argue over. IMO

That's a fact Jack

 

[nkbj]

:redface:
Oh, then Nope.

I'm seeing an interesting shift to the right in groups with the fast twist .40 GPR that might be related to spin but don't know for sure yet.

 

[F.G. Ford]

If you really want to see round ball drift and drop, shoot long distance over still water.
That will forever educate you on what your gun will do over long distance, and values of powder increment.
At 100-200 yds. aim at a stump or any stationary object in the water.
Through out your crono, calculator, and charts!
Fred

 

[Billnpatti]

I am neither a physicist nor a ballistician but my rudimentary understanding of physics is that in order for the rotation of a sphere to move it sidewise, the rotation must be in the vertical plane such that one side of the ball receives more drag than the other causing the ball to curve in the direction of the side having the greater air velocity and thus the greater drag.

Even though I know less about exterior ballistics than some, this is still more of a SWAG than just a WAG. :hmm:

 

[necchi]

No Bill that would be a "wobble".

We really can't compare a baseball throw to rifle or roundball ballistics.

A Curve Ball or other pitches thrown have to do with the physical control of the balls rotation in much different ways then a barrels rifling.

A Curve ball actually has a forward rotation of the ball as it moves along it's flight path creating a drag that causes the ball to drop.

Also Bowling or Billiards, the skilled player can impart spin to the ball that is tangent or perpendicular to the path of the ball making the ball move out of it's direct line.

Likewise when we begin talking about fast twist rifles and bullets, barrel harmonics and exit velocity effect the elongated projectile much differently that a sphere.

A barrels rifling does nothing to impart a spin or rotation to the ball beyond that of the horizontal axis spin.

Any damage too or inconsistency of the rifling near the crown or crown damage it'self can and does allow gases at exit push any projectile off it's course

 

[rodwha]

If I had access to land in an area in which shooting was OK this would be plausible and entertaining, but I do not.

I have a range with a 50, 100, and 200 yds target distance.

What I had figured by looking at a ballistics calculator was to zero at 75 yds as 100 yds has a lot of wind drift, and I've never shot beyond 80 yds anyway.

But looking at the projected path of the ball when zeroed at 100 yds looked great, and would be easier to do at the range.

For a little clarification I don't expect my 80 grn charge to equal from my rifle what they got in their rifle. My question is if I were to know my velocity and plug that in with the formula to figure out the BC of a RB would it not give the same results.

 

[necchi]

My question is;
if I were to know my velocity and plug that in with the formula to figure out the BC of a RB would it not give the same results.

Yes.
And I responded with that answer in my first post to this topic.

It's just that the topic has drifted a little from it's intended path.

 

[rodwha]

I've had many varying opinions, as well as the reply of shoot and see for yourself. I had eventually figured my question may have been a little vague or open to interpretation. I figured I ought to clarify.

Maybe I shouldn't, but there are many here who's opinion carries weight just having read so many responses that gives the impression of knowing what they are talking about, and yours is one of them. But I also want to hear from those who disagree. I like to look at all angles, especially since I don't know. There are a few more modern forums in which I've gone out on a limb and spoken of what I've read here concerning the use of a PRB vs modern stuff. I have a bit of understanding of their part as I was once blind too :haha: