Trajectory Charts?

I've done some googling, but have been unsuccessful in finding graphs of different rounds' trajectories. I'm thinking that it would be good for my understanding to see a chart of a bullet's rise and drop at the various distances.

For example, when trained on the M4, we were told that a 30yd zero is also a 300yd zero because of the bullet's rise from the barrel until it crosses the line-of-aim at 30yds. It continues to rise for a bit, then fall until it again crosses the line-of-aim at 300yds and continues dropping.

I'd like to see a chart for each common caliber to see where they are typically zeroed as well as the amount of drop for longer ranges and bullet weights. I realize this will be affected by the different bullet weights, height of each scopes' rings, and so on... but does anyone publish charts like this?

Have you looked at the balastic calculator at handloads.com? You have to supply the bullet's BC, weight and muzzle velocity. It will give you some pretty good information.

I haven't seen much of such things either........far too many. Most major manufacturers publish (post) some sort of trajectory specs

IDriveB5 said:

Have you looked at the balastic calculator at handloads.com? You have to supply the bullet's BC, weight and muzzle velocity. It will give you some pretty good information.

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I was looking for a graphic chart, but this'll do. Thanks; I hadn't seen this one before.

Might find something useful here. I've never downloaded the program, but it sounds like what you're looking for.

I use the Remington "Shoot" software (joppaj's link above), and it works quite well. Although you can't create new loads, you can customize the velocity and ballistic coefficient of existing loads (obviously, all the provided loads correspond to Remington factory ammo.)

So for example, you can select a .223 55-grain bullet, then override the default velocity and reduce it by say 400 fps, to more closely match the MV from a 16" carbine barrel instead of a 24" barrel. This will give you more accurate trajectory. Don't forget to change the default sight height to 2.6", too. Then set it to shoot a 50-yard zero, generate a ballistics chart, and you'll see exactly how the bullet travels vs. the line of sight at increments all the way out to 1000 yards (the max).

You can print charts and trajectories, too, to take to the range, very helpful when you're sighting in at various ranges.

joppaj said:

Might find something useful here. I've never downloaded the program, but it sounds like what you're looking for.

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Perfect! Thanks. That should be exaxctly what I'm looking for.

I use the cards available here => http://www.ballisticards.com/ extensively. They can also generate custom cards.

MrWhiteRabbit said:

. . . For example, when trained on the M4, we were told that a 30yd zero is also a 300yd zero because of the bullet's rise from the barrel until it crosses the line-of-aim at 30yds. It continues to rise for a bit, then fall until it again crosses the line-of-aim at 300yds and continues dropping. . .

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Ahh yes, the old "rising bullet" misnomer/myth.

The bullet, having absolutely no power of it's own, begins to both lose speed and fall to earth the second it leaves the barrel. If the barrel is perfectly level (perpendicular to the pull of gravity), the bullet will always hit lower than the barrel is pointing.

To provide a zero at various ranges, the barrel is tilted upward in the same manner a thrown ball must be aimed above the distant catcher. The sights will be aligned with the target and the barrel tilted upward under the sights, which is why the bullet may seem to "rise", but, of course, having no external power, it cannot.

Because of the distance (2-1/2") of the sight plane above the barrel in an M4/M16 family of rifles, the sharp upward tilt to align the dropping bullet to the point the sights are aligned at 30 yards (the sight plane) provides a huge amount of tilt, and the barrel is looking quite skyward. So far skyward, in fact, that it's drop happens to coincide again with the sight plane at a much more distant point (300 in the example given).

The problem with canned ballistic charts is that there are too many variables, and while it will give an "indication" of what to expect, it is always an estimate (guess).

Velocity, which weighs so heavily in the calcs, is simply unpredictable from rifle to rifle and barrel to barrel. Identical .308 loads can vary by 150 or more FPS (5%) between identical rifles with different manufacturer's barrels. Add potential/likely barrel length differences and this number can get better or worse. Actual air density at the firing site has a tremendous effect on bullet flight, and is completely ignored by most ammo manufacturers. To compound these matters, each manufacturer tends to be quite "optimistic" with both velocity estimates and the bullet's ballistic coefficient rating. In this month's Precision Shooting magazine, they did an analysis on the .308 Lapua 155 Scenar and it's *actual* measured BC is some 15% below the published figure. How do we account for that?

If you go to StevesPages download site, you can D/L "Armscalc 4.0.1" or "Ballistic 4.13" and generate graphs based on your own data. Just bear in mind that these will be estimates and their sole value is to help with visualizing estimated trajectories. http://stevespages.com/page8b.htm

E.Shell,

You say it's a misnomer or myth, but I think we're describing the same thing. I agree that a bullet won't have any lift of its own, but what I was trying to describe is the path of the bullet, due to the non-parallel nature of the scopen and barrel. Therefore, the bullet will achieve a higher altitude than the barrell (due to velocity and angle) and thereby cross the scope plane twice. I think that's what you said, but am I reading something wrong?

To define this layman's terms:
As you stated, I believe that if the barrel of a rifle is parallel with the earth and fires a round, that round will impact a point of earth short of where the barrel is boresighted.

Therefore, I also believe that a scope, mounted a couple of inches above the barrel, if mounted parallel to the barrel will also be parallel to the ground, and that the fired bullet will will still fall short of where the barrel is pointed, never crossing the point at which the scope is pointed.

Furthermore, I believe that to achieve a true boresight, the point-of-aim for the scope and the point-of-aim for the barrel must cross (and therefore not be parallel lines). So in this example, the point-of-aim for the scope (which is parallel to the ground) will be the same spot of earth, but the barrel will be angled ever so slightly upward (no longer parallel to either the ground or the scope). Now, when the bullet is fired (assuming that the aforementioned spot of earth is at the boresighted zero) the bullet will actually climb (because of the up-tilted and non-parallel barrel, not because of any aerodynamics of its own) and the bullet will therefore make up the inch-or-two difference between the line-of-barrel and line-of-scope to impact that point-of-aim that's on the earth however far in front of the shooter.

Lastly, I believe that when shooting longer distances (beyond the first zero) that the non-parallel barrel will fire the bullet upward, allowing the bullet to cross the scope's point-of-aim once at the near zero (30yd in the example I first mentioned) until it more-fully succumbs to the force of gravity (which, yes, has been acting on the bullet all along) and the bullet begins to fall and cross the scope's point-of-aim a second time at the distant zero (300yd in my example) until impacting the earth a bit further out.

Lookin' for an education...

Mr.WR

MrWhiteRabbit said:

. . . Lookin' for an education...

Mr.WR

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Your understanding is already correct.
You would not believe the number of shooters that take that misused "rise" expression literally.

E.Shell said:

Your understanding is already correct.
You would not believe the number of shooters that take that misused "rise" expression literally.

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*Whew*! Ya had me scared there for a minute. I was about to pull out the old physics textbooks and go back to school!

One of the best analogies I've heard to help understand this is a garden hose and what one must do to squirt a distant target....elevate the hose. All the same elements are in effect...velocity, gravity, distance. BTW WhiteRabbit, some moves are afoot in the military to change from a 25m zero (they do it because it is easy) to a 200m zero. The 200m zero is a much better zero for the M855 62grn Green Tip. The 25m/300m zero will be 2-7" high throughout the incremental distances out to 300m (example is 7.18" high at 150m) and requires the shooter to remember the holds. The 200m zero never rises more than 2" all the way out to 200m (just keep aiming center mass) and will be about 4" low at 250m and 10" low at 300m. It is a much more forgiving zero given typical combat engagement ranges which tend to be 200m or less.

For those that use 62grn and can't zero at 200m, the 50m zero is also a better alternative. Kevin

Kevp said:

One of the best analogies I've heard to help understand this is a garden hose and what one must do to squirt a distant target....elevate the hose. All the same elements are in effect...velocity, gravity, distance. BTW WhiteRabbit, some moves are afoot in the military to change from a 25m zero (they do it because it is easy) to a 200m zero. The 200m zero is a much better zero for the M855 62grn Green Tip. The 25m/300m zero will be 2-7" high throughout the incremental distances out to 300m (example is 7.18" high at 150m) and requires the shooter to remember the holds. The 200m zero never rises more than 2" all the way out to 200m (just keep aiming center mass) and will be about 4" low at 250m and 10" low at 300m. It is a much more forgiving zero given typical combat engagement ranges which tend to be 200m or less.

For those that use 62grn and can't zero at 200m, the 50m zero is also a better alternative. Kevin

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Good Advice!

I found this site useful


http://www.federalpremium.com/ballistics/Ammo_Search.aspx