Skip to main content
Help Center Community Shop

General Ballistics Question

prenger745
I am new (obviously) to actually looking at ballistics etc. My question is this. When looking at a graph of the path of a bullet, how come at Zero yards the bullet is in the negative area. For example, a 204 Ruger Vmax 32 Grain at 0 yards is at -1.555 inches. Its seems to me at 0 yards..it would be 0 inches.

Thanks,
Dan
0

Comments

5 comments

Date Votes
  • MIKE WISKEY
    thats the height of the scope or other sighting devise over the top of the bore. if you put the muzzel of a rifle tight against a wall and fired it the bullet hole would be 1.5" (approx.) below the spot your scope was looking at
    0
  • gunnut505
    There's the line-of-sight, the path the projectile takes, and the height above the bore of the optics.
    The projectile will "rise" to the line of sight, cross it; and then start to drop past it.
    When optics are used, the extra inch or so that they are above the centerline of the bore will have to be included in your ballistic calculations to figure out the path the projectile will take.
    Thus, if you work up a chart, the "0" yardage figure will show the projectile being underneath the line of sight.
    Hope this helps!

    And welcome to the forum!

    For more information on ballistics, read Bob Forker's book," Ballistics for shooters"

    "Qui non est hodie cras minus aptus erit" --OVID
    0
  • prenger745
    Thanks so much for the quick reply! As soon as I read your reply it made perfect sense. Do any of you use the program 'Shoot!'? That is where I was looking at ballistics graphs and charts. My neighbor just yesterday bought a savage in .204 Ruger and I had not heard much about the round, so pulled it up on 'Shoot'

    Again, thanks!
    0
  • Hunter375
    prenger-
    The .204 Ruger is basically a necked-down .222 rem mag. While it really has no advantage over the .22-250 or .220 swift, it does explore the possibilities of a caliber that has been obsolete since remington dropped the 5mm rimfire magnum. It will provide 220 swift velocities with lower recoil and muzzle blast, but at the price of energy since it fires a lighter bullet.

    As to the line of sight question, your bullet will cross twice; once at a relatively close range, and again at the sighted range. Your ballisic programs graphs should illustrate this. You will also see positive numbers betwwen the first "zero" and the second.

    For example, your .204 will show a bullet impact of -1.5" @ 0 yards, 0" @ ~70 yards, +.52" @ 150 yards and 0" again at 200 yards (if zero range is 200 yards)

    It's easy to spot liberals-they are the ones who have no assets to protect and need every handout they can get. They have forbeyed themselves ascendence to a productive lifestyle.
    0
  • heavyiron
    Prenger,

    The measurement of -1.555 at 0 yards is calcuated as the difference from the line of sight and the path of the bullet (at zero yards the path of the bullet is the same as the axis of the bore because both the bullet and bore are at the same location). The line of sight (LOS) and the bullet path (trajectory) are used as reference datum in exterior ballistics. The LOS is a straight line through the sights to the target.

    Generally for exterior ballistics, 1.5 inches is used to approximate the height conventional sights above the bore of the gun as aptly stated by Gunnut. If you think of the positioning of the sights and the gun barrel, the sights are always higher than the bore. Therefore, the bullet starts its flight minus 1.5 inches below the LOS or axis of the bore. Since all bullet paths are measured from the LOS, the bullet ordinate is either plus (+) inches above the bullet path or minus (-) inches below the bullet path. Bullet path is also called trajectory and is not a staight line but a smooth curve due to the effect of gravity and other forces.

    Using the old ballistic tables usually considered a 1.5-inch sight height, but if someone's gun had a 2.0 or 2.5 or even 1.25-inches sight height, the tables were all off and could only approximate the location of the bullet at any given range. Additionally, all the old ballistic tables used stand temperature, pressure, altitude, and humidity. That was the old days.

    The new computerized exterior ballistics software is completely different. The new software can really make "dead-on" calculations of the bullet position. Most good ballistic software will now allow the user to determine the sight height and therefore, customize ballistic tables for their individual rifle. Additionally, the new software can include all variables such as temperature, altitude, pressure, and humidity for precise predictions of the bullet trajectory.

    I hope this helps. Exterior ballistics can be a confusing topic.

    Regards,

    Heavyiron

    bullitt_county_4199_small.jpg
    "If I don't see you nomore on this world, I'll meet you on the next one, and don't be late!" - Jimi Hendrix
    0

Please sign in to leave a comment.

Recent Activity