Ive just begun reloading the past year, so please forgive me if this is an ignorant question.
I am curious as to the math to find out how much a bullet drops at different distances. I have seen ballistic tables, that list FACTORY loads, and how much the drop is from 50-400+ yards.
But what about handloads? There has to be some way to mathmatically figure out how much a bullet, going x fps, weighing y grains, is going to drop at different distances. Any help would be appreciated.

Go to huntingnut.com and on the right hand side is a free download of Pointblank. Put in the velocity and you can set all the other parameters. If you need further help, post questions.

http://www.huntingnut.com/

The point blank program works pretty well, but it is always best to verify with a bit of shooting. Every once in a while, you will get a big surprise where the drop just doesn't come out the same as on paper.

CC,

You indicated in a related post that you have just been working with your first reloads. I'd suggest that as soon as you are able, that you invest in chronograph. You cannot reliably determine the velocity of your reloads without one. You can get a Chrony or other inexpensive chronograph for about $100. The cheap ones are as accurate as the expensive ones, just fewer bells and whistles.

With velocity data you can see what your pressures arae doing in your rifle and you can compute bullet drop and lots of other good stuff. Kudude

Ditto. But without a chrono you can get amazing velocities!

quote:

Originally posted by kudude:
...With velocity data you can see what your pressures arae doing in your rifle ...

Actually, that is simply WRONG!

You can not tell about the "Pressure" from reading a Velocity due to all the variables in the Cartridge components, Chamber and Bore. However, you will be "totally mis-lead" by believing that you can.

quote:

Originally posted by Will:
Ditto. But without a chrono you can get amazing velocities!

Yes.....just ask the AI guys!!!!!

quote:

Originally posted by Hot Core:

quote:

Originally posted by kudude:
...With velocity data you can see what your pressures arae doing in your rifle ...

Actually, that is simply WRONG!

You can not tell about the "Pressure" from reading a Velocity due to all the variables in the Cartridge components, Chamber and Bore. However, you will be "totally mis-lead" by believing that you can.

In all fairness to Kudude it must be stated that the chronograph is a key tool in estimating pressures.

If one is getting velocities less than the reloading books call for it isn't at all an indication that pressures are low. However if one is getting velocities in excess of what the loading books are calling for this just might be a strong indicator that pressures are higher than one might want.

It's simply a piece of (valuable) information to help the reloader estimate pressures.

One absolutely must not assume linearity or correlation.....it's truly a horrible assumption.

You can get estimates on paper but there is only one way to actually find out. Sight the gun for your normal distance. Go out and set a target every 50 yd's all the way as far as you are ever going to shoot. Use large cardboard behind the far ones.I used to go to 600 yd's with a varmint rifle that was sighted for 350 yd's. I would shoot several shots at every target from 100 to 600 all at one time using a center hold. Just move from one target to the other. You will have to stagger some out of line. Measure the shots to the bull and record it on a piece of paper and tape it to your scope.
The actual drop or in case of the close targets, the high hits, never matched any figures printed or worked out. Some were close but would not buy a woodchucks head at 550 yd's or more. The hardest shots with my settings were actually 100 to 250 yd's because I had to aim just the right amount low. I would just use a .44 mag SBH to 100 yd's, a Remington .222 out to 300 and the .220 Swift to 600. The Swift was so accurate, I once put 5 shots in 1/4" at 350 yd's. It was a pre 64 model 70, bedded and floated with a Balvar 6X24 scope. I used the 60 gr Hornady but don't remember the load.
It is really a lot of fun doing this, much better then messing with paper and pencil.

So you want to do the math? You might be a glutton for punishment, but here's a little excerpt from the $70 Ballistic Explorer program from Dexadine, Inc.

Basic Exterior Ballistics Theory

Ballistics theory states that bullets of different diameters and weights, but of similar shapes, decelerate in constant proportion to each other. That is, if a bullet's deceleration is twice that of another similarly shaped bullet at one velocity, then that bullet's deceleration remains twice that of the other bullet at any other velocity. Thus, by knowing a bullet's deceleration at one velocity, its deceleration at a second velocity can be predicted by knowing the deceleration of a similarly shaped bullet at both velocities.

To make the theory useful, a number of "standard" bullets have been test fired thousands of times to determine their deceleration at many velocities. This experimental data is then mathematically analyzed and a curve (function) that best matches the experimental data is produced. Deceleration is the result of drag due to air resistance, so these functions are called drag coefficient functions. When these functions are expressed in the form of tables, we call them drag coefficient tables or just drag tables for short.

The two main forces acting on a bullet in flight are gravity and drag due to air resistance. In horizontal flight, gravity causes the bullet to accelerate (drop) toward the ground while drag causes the bullet to decelerate (slow down). While unconventional, it's useful to express drag in gravitational units (G). A force of one G is equivalent to the force exerted by gravity on an object near the surface of the earth. Ignoring air resistance, a free falling object accelerates at 32.17 f/s². That is, after one second of falling, the object's velocity is 32.17 f/s, after two seconds its velocity is 64.34 f/s (2 x 32.17), after three seconds its velocity is 96.51 f/s (3 x 32.17), and so on. Likewise, an object thrown straight up decelerates at 32.17 f/s². Incidently, the names of most drag functions start with the letter G in honor of the Gâvre Commission in France (1873-1898) and not because of gravitational units.

The figure below shows the standard drag functions G1, G5, G6, and GL plotted as G force for velocities from Mach 0.5 to Mach 4.5. Mach 1 is the speed of sound, which is 1116.5 f/s at standard conditions.

**INSERT G-FORCE VS MACH NUMBER GRAPH**

Each of the drag functions is based on a standard projectile of a particular size and shape. For example, the G1 function is based on the Krupp projectile which has a flat base, and is 3.25 calibers long with a 2 caliber ogive tip.

The speed of sound in air is affected by temperature and somewhat by humidity, but not at all by pressure (altitude). As temperature increases, the speed of sound also increases. The air resistance felt by a bullet depends both on the density of the air and the speed of sound through that air. This is why drag functions are defined in terms of Mach number rather than absolute velocity.

At standard conditions, a test bullet's deceleration and corresponding Mach number can be calculated from an initial velocity (V1) and another velocity (V2) at a known distance down range using the following formulas:

(V1² - V2²)

Decel = --------------------

Distance x 2

(V1 + V2)

Mach Num = ----------------------------

Speed of Sound x 2

The values of V1 and V2 can be obtained experimentally using two chronographs. The Ballistic Coefficient (BC) of the test bullet is the ratio of the standard bullet's deceleration divided by the test bullet's deceleration at the same Mach number.

Deceleration Of Standard Bullet

BC = ------------------------------------------------------

Deceleration Of Test Bullet

If the test and standard bullet's shapes are similar, then the BC will remain nearly constant over a wide range of velocities. Thus, the suitability of a particular drag function can be gauged by calculating a second BC for the test bullet using significantly different values of V1 and V2.

To the degree that the part of the drag function spanned by V1 and V2 is nonlinear, an error is introduced into the calculated Mach number, and thus, into the calculated BC. This error as well as those introduced by non-standard conditions and winds can be corrected for.

Hey VapoDog, I applaud your ability to cover both sides of the fence, the top of the top rail, the bottom of the top rail and each side of that same rail.

Concerning "Pressure" and "Velocity" using a Chronograph, no worthwhile coorelation can be made.

I realize that stomps on a lot of toes, but I really have no malicious intent toward Kudude. It is a common mis-conception among Chronograph users that by measuring a Bullet's Velocity that it directly coorelates to a Random Velocity and Random Pressure indicated within a Load Manual.

I will agree that sure would be nice if it did. And I'll even admit that at one time in my life, many years ago, I also got sucked-in to believing that just because I was using a specific amount of Powder listed in a Manual that if I got the same(or close to the same) Velocity that the Pressure must also be the same as what was shown in the Manual - that was WRONG-O!

When you measure the Velocity of a Bullet using a chronograph, your Pressure might be less than, the same as, or more than what is shown in a Manual.

Any attempt at trying to "decide" if a Load is at a SAFE Pressure Level, based "only" on Velocity simply indicates the person doing the Loading just doesn't understand how all the variables can affect the actual outcome.
---

Fortunately there is a tried and true way for people to prove to themselves that Chronographs do not tell "useful" information concerning Pressure.

Get a group of your buddies that all have rifles chambered for the same cartridge and have them meet you at the Range with the Chronograph. You can probably tell on just two rifles, but take as many as you can so no one dis-believes the results.

You will need enough of "your Loads" to shoot 3-5 shots through each rifle.

Take along the good old 0.0001" capable Micrometer to measure PRE and a Data Sheet.

Measure the Velocity and PRE for each rifle and Average each. Now sit back and look at the Data.

Hot Core,

I am not a ballistical expert or physics prof (and I didn't spend last night at a Holiday Inn Express), but I don't think you are correct in stating, "It is a common mis-conception among Chronograph users that by measuring a Bullet's Velocity that it directly coorelates to a Random Velocity and Random Pressure indicated within a Load Manual."

First, there is nothing random about the velocity, or the pressure reported in loading manuals. Most ballistic labs shoot a statistically significant number of test shots to arrive at their data. I know that I do in working up loads.

SEcond, while manuals vary, they are generally more "consistent" that "inconsistent" in stating the upper limits of a given load; certainly within the variance one would expect for differences in lots of powder, bullets and primers.

I use my chronograph to determine how fast my bullets are going; how uniform the velocities are; and give me a insight into the load's pressure in load development. I am well aware that a chronograph is not a pressure barrel. However, if I have followed a recognized recipe for a given loading, obtain velocities in the same range as those reported by others, and have no other indications of excessive pressure, I am comforted by my findings. On the otherhand, if my velocities are up and I have any pressure signs, I ease off the throttle.

The more interesting situation is when you get higher velocities and no pressure signs. This is when you must use other measures and lots of common sense, and raises the third point: "There is no such thing as a free lunch."

If you have a bullet that is going faster than predicted, it required more pressure that was obtained by the recipe's(s')source to do it. This "added" pressure may be from a tight chamber, pressure on the bullet neck, or ammunition that was fired that had been sitting in the sun. But the energy imparted to the bullet was higher.

The energy input can only be increased by having the force work on a given caliber and weight bullet longer (longer barrel) or having more force, ie, pressure. Adjustments in velocity should be made for barrel length to "equalize" the comparisons. That leaves only pressure increase to account for the higher velocity.

Whether the pressure generated was within the limits of the rifle and the case is a different matter, but if the velocity is higher, then the energy had to be higher all other things being equal.

There is a great debate between pressure barrel advocates, piezzo electric measurement of barrel elasticity, and "case web" measurers. I don't have the money and shoot too many calibers to consider the pressure barrel approach; I don't want to have wires stuck all over my rifles, therefore, piezzo is out; and don't need to push the upper limits of the curve enough to waste my time measuring case webs. (I did for many years, but I now am convinced the results are as reliable from reading tea leaves.)

For the money and for the information generally provided, to include the ability to look up bullet drop from a table simply, the $70 to $100 spent on a chronograph is the best money a beginning reloader going to spend. He will move from a "guesser" to a "knower" at least on his velocity. And that ain't all bad. Kudude

Hey Kudude, Nice well thought out response. I do stand by my previous statement that, "It is a common mis-conception among Chronograph users that by measuring a Bullet's Velocity that it directly correlates(corrected spelling on my original mis-spell) to a Random Velocity and Random Pressure indicated within a Load Manual." If you ever have the opportunity to Test multiple firearms of the same caliber with the same load, you will see what I was talking about.

quote:

I am not a ballistical expert or physics prof (and I didn't spend last night at a Holiday Inn Express), but I don't think you are correct in stating, "It is a common mis-conception among Chronograph users that by measuring a Bullet's Velocity that it directly coorelates to a Random Velocity and Random Pressure indicated within a Load Manual."

First, there is nothing random about the velocity, or the pressure reported in loading manuals. Most ballistic labs shoot a statistically significant number of test shots to arrive at their data. I know that I do in working up loads.

I agree with the Labs shooting a “significant number of shotsâ€. By Random, I was referring to selecting one from a Manual and using it as if it was the exact Velocity a person should expect to get with that specific Load in any firearm. If you compare just two Manuals(the more the better though), it becomes quite obvious that a specific amount of Powder with a specific Bullet Weight just doesn’t equate to the same Velocity in each Manual.

So by Random, I mean an arbitrary decision to use a specific Velocity from one source. If a person looks at more than one Manual, it becomes clear there is no specific Velocity a person can use as a Benchmark Standard with all firearms.

Look back a few weeks and you will always see the Beginners asking , "Why is there a disparity among the Manuals?" It is a common theme on every Beginner’s mind. But the same issue somehow gets rationalized away when a person begins using a Chronograph and they grasp onto one (Random) Velocity as being the Universal Benchmark Standard – which it isn’t.

quote:

Second, while manuals vary, they are generally more "consistent" that "inconsistent" in stating the upper limits of a given load; certainly within the variance one would expect for differences in lots of powder, bullets and primers.

Rather than argue the point, I’ll give you a classic example of how I’ve seen this concept to be incorrect. I’ve used this specific example a few times on this Board, so if it looks familiar you probably saw me use it before.

Using an old Ruger M77(tang safety) in 7mmRemMag, I could SAFELY use 2.0gr of H1000 above any Load I ever saw listed in a Manual. It shot well and gave no indication of being Over Pressure with any of the traditional Pressure Indicators as well as CHE/PRE.

Then I got a new Remington M700 in 7mmRemMag and it reaches a SAFE MAX 4.0gr lower than the old Ruger with the exact same components. The Remington Velocity is also slower than the old Ruger. A person simply can’t reach the same Velocity in this Remington that can be reached in the Ruger, at SAFE pressure levels.

quote:

I use my chronograph to determine how fast my bullets are going; how uniform the velocities are;

I can agree with that.

quote:

and give me a insight into the load's pressure in load development.

But, I’d suggest to you that you have been mislead into thinking this is true. If you do nothing other than gain a "skeptical attitude" about the Pressure from our discussion, it will become clear to you what I’m saying, the more you use the Chronograph on multiple firearms.

quote:

I am well aware that a chronograph is not a pressure barrel. However, if I have followed a recognized recipe for a given loading, obtain velocities in the same range as those reported by others, and have no other indications of excessive pressure, I am comforted by my findings.

I can agree with this statement. Here though, you are not trying to attribute some unknown Pressure with your results.

quote:

On the other hand, if my velocities are up and I have any pressure signs, I ease off the throttle.

Excellent idea.

quote:

The more interesting situation is when you get higher velocities and no pressure signs. This is when you must use other measures and lots of common sense, and raises the third point: "There is no such thing as a free lunch."

This will sound a bit VapoDog-ish(both sides of the fence) in regard to my previous comments, but perhaps what appears to be High Velocity for that specific Load is what it really should be(for that specific firearm) and not what is in the Manual, or whatever Velocity is (Randomly) selected as the Universal Benchmark Standard.

quote:

If you have a bullet that is going faster than predicted, it required more pressure that was obtained by the recipe's(s')source to do it. This "added" pressure may be from a tight chamber, pressure on the bullet neck, or ammunition that was fired that had been sitting in the sun. But the energy imparted to the bullet was higher.

Let me suggest to you that the exact opposite might be true also. Visualize two firearms being tested. If for example the Bore of rifle #1 has Less Drag on the Bullet than rifle #2, then you have the potential to obtain a Higher Velocity with the same Load due to less friction.

This is not a universal truth though, because some will do just as you mention, even with less Drag.

quote:

The energy input can only be increased by having the force work on a given caliber and weight bullet longer (longer barrel) or having more force, ie, pressure. Adjustments in velocity should be made for barrel length to "equalize" the comparisons. That leaves only pressure increase to account for the higher velocity.

I understand your thoughts, but they do not account for the minute variations in Chamber and Bore dimensions, the actual Bore Finish condition and Lot-to-Lot variations in the Cartridge components.

quote:

Whether the pressure generated was within the limits of the rifle and the case is a different matter, but if the velocity is higher, then the energy had to be higher all other things being equal.

This is really where a person can be mislead, because you changed the word Pressure to energy in that statement. I agree that with Higher Velocity for a given Bullet weight, you will indeed have more Energy available. However, that does not necessarily equate to a Higher Pressure.

quote:

There is a great debate between pressure barrel advocates, piezzo electric measurement of barrel elasticity, and "case web" measurers. I don't have the money and shoot too many calibers to consider the pressure barrel approach; I don't want to have wires stuck all over my rifles, therefore, piezzo is out; and don't need to push the upper limits of the curve enough to waste my time measuring case webs. (I did for many years, but I now am convinced the results are as reliable from reading tea leaves.)

We completely AGREE.

quote:

For the money and for the information generally provided, to include the ability to look up bullet drop from a table simply, the $70 to $100 spent on a chronograph is the best money a beginning reloader going to spend. He will move from a "guesser" to a "knower" at least on his velocity. And that ain't all bad. Kudude

I can agree that he will at least know his Velocity.

Now, as long as he does not try to rationalize some unknown Pressure with the Velocity, he will be on the right track.

By the way, once you know the Velocity, (other than being mislead about the Pressure ) what do you do with it?

In response to the original question, if you really like to play with math, get a copy of 'Hatcher's Notebook'. It is all in there. You can do it with a calculator( very tedious) or with a computer if you have any programming skills. Later Sierra loading books also have quite a lot of info on the subject.
C.G.B.

Hot Core

Velocity does relate to pressure. The same way bullet energy relates to both. You're right that you cannot read pressure directly off a chronograph, but if you know the correct formulas you can make very reliable estimates of pressure. I still use my old Powley Computer for load development and I also have the companion "Powley psi calculator" which does exactly what you say cannot be done. All aspects of internal and external ballistics are directly related to each other. It's all part of physics and I always tell new shooters that physics is Mother Nature and you can't fool her no matter how hard you try.

There was a time, not too long ago, when there was no such thing as electronics. Bullet velocities could be determined by shooting a ballistic pendulum. Knowing the velocity, energy, bore size (expansion ratio), powder weight and energy, mathamatical formulas were used to determine both pressure and exterior ballistics. The results were not 100% accurate but then neither are the output from todays ballistic programs.

quote:

Originally posted by Cheechako:
Velocity does relate to pressure. ...The results were not 100% accurate but then neither are the output from todays ballistic programs.

Hey Ray, That is the basic problem.

When you read these posts, imagine yourself as a Beginner who has no idea what is really going on. There are lots of posts that "mislead" that Beginner into thinking he can use a Chronograph and not have to worry about Pressure at all.

I've read enough of both your posts and Kudude's posts to know neither of you think that way. I'd guess you both use about every traditional Pressure Indication Method available.

The problem comes in when the Rookies just don't get it, but think they do.

How many times do we see the TOTALLY FALSE Pressure = Velocity statements from people who would never intentionally mislead anyone, let alone a Beginner.
---

I always try to think of the Rookies and how easy it is for them to be mislead. That is why I bother to come in and challenge these kinds of issues. And I hope that more folks will do the same - once they understand where I'm coming from.

Best of luck to you.

Hot core

You are absolutely right on all points. I had the same thoughts. I'll bet we lost Chromosone Cowboy a long time ago and that's too bad. Us oldtimers need to leave a better path for the new guys to follow but it's easy for us to get caught up in a lively discussion. I try not to but can't help myself most times.

Ray

Calculations and tables are still estimates. If you are really planning on shooting at the distances where it's critical, you need to practice at those ranges.

This will give you time behind the trigger, wind doping experience at distance, and will help you learn how much YOUR rifle, with YOUR load, drops and drifts.

Tables, charts, ballistic programs will put you in the ballpark. But it's still not like playing the game. Nate

All of you are making my brain turn to mush. Just go out and shoot the darn gun. Is that so hard?

Hey Ray, At the chance of turning "bfrshooter" into a Democrat (brain turning into mush) , I really figured you, Kudude and I think a lot alike.

Any help you can provide by watching out for things that can mis-lead the Beginners would certainly be appreciated. Occasionally it only takes a word or two in order to clarify a statement so they don't get started on the wrong track.

Nope, no matter what you do to me, even 9/10's of my brain to mush, would not a democrat make!

quote:

Originally posted by bfrshooter:
Nope, no matter what you do to me, even 9/10's of my brain to mush, would not a democrat make!

Gald to hear it.

quote:

Originally posted by Hot Core:
Hey VapoDog, I applaud your ability to cover both sides of the fence, the top of the top rail, the bottom of the top rail and each side of that same rail.

Concerning "Pressure" and "Velocity" using a Chronograph, no worthwhile coorelation can be made.

I thought you'd like that.....

But in fact it was a truthful statement and just for grins I reitterate.....The Chrony can be an excellent tool for helping estimate pressures as long as one understands that pressure and velocity are NOT directly correlated nor is the relationship linear.

In other words.....High velocity likely means hi pressure.....but low velocity does not at all mean low pressure.

It's not likely that one using a .270 driving a 130 grain bullet at 3,200'/sec is less than 60,000 PSI......but entirely possible that the same guy and rifle shooting the same bullet at 2,800'/sec might actually be at 65,000PSI

Velocity is not at all (necessarily) proportional to pressure.

Velocity is a pressure indication. We can discuss it all anyone wants, but it's pressure that drives the bullet. Sometimes it really is just that simple...

That's all for me.

Jaywalker

quote:

Originally posted by Jaywalker:
Velocity is a pressure indication. We can discuss it all anyone wants, but it's pressure that drives the bullet. Sometimes it really is just that simple...

That's all for me.

Jaywalker

Actuly it's work under the curve that drives the bullet, Example a pressure curve that spikes at 65000psi but only lasts .000001sec won't get you the velocity of one that only goes to 55000 but lasts for .0001 sec.

It's easier to visualize if you plot pressure vs time on some graph paper, the curve with the most "squares" below the line will produce the highest velocity. Like this /\ (fast powder) vs /-----\ (slow powder).

Hey VapoDog, Here I thought you had it "all covered" and now you go back and cover the "ends" of that top rail as well.

quote:

Originally posted by Jaywalker:
Velocity is a pressure indication. .. Sometimes it really is just that simple...

Hey Jaywalker, To me, that is the exact problem - a lot of folks believe "it really is just that simple" - when in reality it is extremely complex.

You don't need to believe me or anyone else, but I would encourage you to view any association you might make between a Velocity and Pressure with a good dose of skepticism. If you do, you will eventually see indications that change your mind about it being simple.
---

Hey Tailgunner, Excellent post that is right on the nose!

quote:

Originally posted by Tailgunner:

quote:

Originally posted by Jaywalker:
Velocity is a pressure indication. We can discuss it all anyone wants, but it's pressure that drives the bullet. Sometimes it really is just that simple...

That's all for me.

Jaywalker

Actuly it's work under the curve that drives the bullet, Example a pressure curve that spikes at 65000psi but only lasts .000001sec won't get you the velocity of one that only goes to 55000 but lasts for .0001 sec.

It's easier to visualize if you plot pressure vs time on some graph paper, the curve with the most "squares" below the line will produce the highest velocity. Like this /\ (fast powder) vs /-----\ (slow powder).

Here we have a good dose of integral calculus in action......and I thought we had a difficult time trying to understand Standard Deviation.

Good post but might be a bit over the heads of the average reloader......still paying attention here Stonecreek?

quote:

Hey VapoDog, Here I thought you had it "all covered" and now you go back and cover the "ends" of that top rail as well. Big Grin

HotCore...it's a practiced trait.......Thanks

quote:

Velocity is a pressure indication. We can discuss it all anyone wants, but it's pressure that drives the bullet. Sometimes it really is just that simple...

It would be nice if things could always be that simple.......Hey....if this is your final word on it ....well...that's OK with me but the post above about work under the curve is hitting the truth dead center.....sorry if simple isn't the solution here.

[quote]
Good post but might be a bit over the heads of the average reloader......[quote]
Boy Ill say.
After reading all of this, Ive decided reloading is over my head, and its time to quit.

Don't quit! The reason I say to shoot the gun is because I was never that good in math and am now so old I forgot any I did learn.
There are a lot of smart guys on this site but they would have to come over here and sit and explain every step to me. Most likely still go over my head.

Cowboy
To answer your origional question (which I didn't do) Drop calculating has only a couple of variables that we reloaders can control, those being the "BC" of the bullet (the higher the BC, the easier it slips through the air), and muzzle velocity. There are any number of balistic calculators on the net, where all you have to do is "plug in the numbers". Note, that while they can get you close for scope settings (windage and elevation) for longer ranges, you NEED to verify your loads by actual field shooting, however they are great for making compairisons between different bullets/loads.