Is Faster or slower generally best?

[bpcr shooter]

Here is the $64,000.00 question.

So, what do we do when: We know exactly the BC of the bullet and the mv, then correctly calculate the ballistics by tables, fire the shot and it lands nowhere near where we calculated that it should ? Given a no wind, no mirage condition with a light overcast 12 O'Clock sun time.

When this happens.........You adjust. But why is is not hitting where it is supposed to in the first place? Coriolis effect?, humidity?, what was the orig zero, was it correct??, there is also with our lead bullets, set back of the nose changing the B.C.. All I know is when I put in dope its just a starting point, thats it.

[BFD]

Here is the $64,000.00 question.

So, what do we do when: We know exactly the BC of the bullet and the mv, then correctly calculate the ballistics by tables, fire the shot and it lands nowhere near where we calculated that it should ? Given a no wind, no mirage condition with a light overcast 12 O'Clock sun time.

When this happens.........You adjust. But why is is not hitting where it is supposed to in the first place? Coriolis effect?, humidity?, what was the orig zero, was it correct??, there is also with our lead bullets, set back of the nose changing the B.C.. All I know is when I put in dope its just a starting point, thats it.

If the "dope" is right and complete, the bullet hits where it was predicted to hit. Simple as that.

[desert deuce]

BPCR Shooter wrote: All I know is when I put in dope its just a starting point, thats it.

Exactly, the word estimate just doesn't quite describe it. More a nonscientific wild ass guess at times and so gratifying when your nonscientific wild ass guess turns out to be spot on. It is easy to remember and recall those moments. The others, not so much.

In a match, how often is your first sighter and first record shot in the X-ring at 1,000 yards say at Ben Avery, Raton or Byers?

At ranges like Tucson where the line of sight is above most of the flags that first sighter is truly a non scientific wild ass guess and your historical shooting notes are your best resource.

[bruce m]

Here is the $64,000.00 question.

So, what do we do when: We know exactly the BC of the bullet and the mv, then correctly calculate the ballistics by tables, fire the shot and it lands nowhere near where we calculated that it should ? Given a no wind, no mirage condition with a light overcast 12 O'Clock sun time.

When this happens.........You adjust. But why is is not hitting where it is supposed to in the first place? Coriolis effect?, humidity?, what was the orig zero, was it correct??, there is also with our lead bullets, set back of the nose changing the B.C.. All I know is when I put in dope its just a starting point, thats it.

If the "dope" is right and complete, the bullet hits where it was predicted to hit. Simple as that.

too true.
it is just a matter of getting it right.
as zack says, part of that can include notes on local ranges.
bruce.

[mdeland]

One other aspect of this subject that has not been mentioned is that as velocity decreases the BC of a bullet increases. So not only does the low velocity .22 ammo start out with a higher BC bullet advantage than the high speed stuff it actually increases the farther down range it flies.

[BFD]

Have you ever measured or looked up the starting BC of a .22 bullet?

[mdeland]

Not lead as I don't have a chart for but jacketed 40 grainer at 2000 fps is in the .130 range.

[mdeland]

I did find a chart on line that tested Eley Tenex and RWS 50 for Bc. Both were round nose target bullets at 40 grains each.
At 1047 fps the Bc was .145 and at 905 fps it was .192.

[bruce m]

so what does this tell you about drag and velocity, particularly in the transonic zone?
bruce.

[mdeland]

The 30 grain bullet was .108 BC at 1047 fps and .144 BC at 905 fps. I which it also had a time of flight column.

[bruce m]

mike,
so what about the drag velocity question?
bruce.

[mdeland]

Well it confirms what we all know , that is, more velocity more drag, less velocity less drag. The BC improves as the speed declines. I don't see from these figure though a direct correlation between drag and deflection which is what I'm trying to understand if true or not.

[bruce m]

mike, the more drag, the more the bullet slows down.
the more it slows down, the more deflection it sustains.
it is a function of rate of loss of velocity.
you might find on the net, graphs of drag vs velocity above, during, and below transonic.
typically drag slowly increases as it comes down to top transonic speed, then drops rapidly during the transonic zone, and as it comes out of transonic starts to rise again slowly.
the b.c .graph is the opposite.
this is the reason sierra gives different b.c.s for different velocity ranges.
just found one under the heading "drag coefficient from a ballistic drop table." if you type that in a search engine.
bruce.

[mdeland]

Remember the slow-mo video of the patched bullet and how it revealed that the patch is actually being stripped from behind from the compressed barrel air coming out of compression after clearing the muzzle. Before this video we all assumed it was the slip stream of air causing it to be removed from the front end but the video revealed that not to be the case. I've seen this scenario repeated time and again over my life time of shooting as we progress in our understanding of things. I think this may be one of those times again in our understanding advance as we re-investigate what has been generally excepted as fact and may not be the complete story.

[bruce m]

mike,
you seem to be keen to condemn what is known and able to be calculated methematically without trying to understand it first.
bringing patch stripping into this discussion is absolutely futile and pointless.
it appears to be a way of avoiding the point of the discussion by taking it somewhere else.
the fact that if you have a zero of some kind on a rifle, you can calculate sight adjustments for any other range accurately with all factors taken into account proves the point.
it is so calculateable that long distance disciplines have had to ban the use of labradar chronographs in competition.
this is because if a shot goes high or low, and velocity reflects this, that shooter has a calculateable advantage.
the same with deflection if you can feed ALL the factors into the equation.
and spindrift as well.
if you are going to understand this you need to do the work necessary to do so without avoiding the issues.
before you can play jazz, you first of all have to learn to play the instrument.
bruce.