A Dumb Question About Trajectory

[SPYDERLK]

Yes. ... Left unsaid, but clear in the graphic, it is the bores offset below the sight that influences the angle where sight and trajectory cross. - This makes a guns characteristic different with regular vs telescopic sights since the telescope sets higher above the barrel.

With standard sight a 30-06 set dead on at 30 yds shoots real good out to about 300. ... AIR, it goes about 2" high at ~100yds and about 4" low at 300.

With scope, higher above the barrel, the 30yd sight in will require a more acute upward correction. Thus the bullet will rise higher above the sight line before beginning to drop.

On a technical point...not trying to be **** about it.

The laws of physics state that the bullet starts to drop the instant it leaves the muzzle...aerodynamics of a spinning projectile (not velocity) resists the force...fired in 0 atmosphere (total vacuum) a bullet would not rise...

Air density and pressure are key factors in sniper training...

Only if fired horizontally does drop start immediately. A bullet fired upward is not dropping; its rise is being slowed. The bullet is rising wrt the sight line at first. It is rising more slowly as time progresses. This upward component is decreased by gravity to zero - at which point drop commences.

What do you mean by this? -- At face value its definitely wrong.
,,,larry

 

[RedNeckGeek]

On a technical point...not trying to be **** about it.

The laws of physics state that the bullet starts to drop the instant it leaves the muzzle...aerodynamics of a spinning projectile (not velocity) resists the force...fired in 0 atmosphere (total vacuum) a bullet would not rise.

More correctly put: gravity accelerates the bullet downward starting the instant the bullet leaves the barrel. If the barrel is tilted upward, the bullet will rise until the initial vertical velocity imparted to it by the inclination of the barrel is overcome by the acceleration of gravity.

I would expect the aerodynamic effect of the spinning projectile to be too small to measure at most small arms distance. The spinning does stabilize the bullet so that it flies point first though, and should it instead tumble aerodynamic drag would slow the bullet much more rapidly.

 

[Industrial Toys]

I have been bogged down with work snce I posted this topic. The replies are very, very interesting and informative. I will have to study this material more closely in the coming weeks when I hope, my work load abates somewhat.

 

[Industrial Toys]

We fired tens of thousand of rounds of military calibers back in the eighties but never stopped to study the physics. At times we were clearly confused as to the results we were getting at varying ranges. Now it all starts to make sense. I am a little confused about the post that states:

With standard sight a 30-06 set dead on at 30 yds shoots real good out to about 300. ... AIR, it goes about 2" high at ~100yds and about 4" low at 300.

Is being 4" down at 300 yards considered shooting good?



On a side note. I also fired tens of thousand of .177 pellets as a kid using a Chec. air rifle, that I still have. Never once did I encounter what I encounterd recently (with a new air rifle). Pellets were refusing to leave the barrel! It seems that the pellet skirts are a little too wide. Pressing them in with a pointed object solves the problem but this is a big PITA!

 

[tcartwri]

And just curious, but how flat is the trajectory of a department store quality pellet rifle?

Thanks

Pellet guns are limited to 500 feet per second in Canada, before they are considered a firearm. ie you would need your PAL to buy one. Therefor your Canadian Tire special is not flat at all.

My crosman drops a good 3" at only 30 yards.

Ok, maybe not 3", but it is significant.

 

[SPYDERLK]

We fired tens of thousand of rounds of military calibers back in the eighties but never stopped to study the physics. At times we were clearly confused as to the results we were getting at varying ranges. Now it all starts to make sense. I am a little confused about the post that states:

With standard sight a 30-06 set dead on at 30 yds shoots real good out to about 300. ... AIR, it goes about 2" high at ~100yds and about 4" low at 300.

Is being 4" down at 300 yards considered shooting good?

It just shows the flatness of trajectory. ... The gun sighted dead on at 30yds is w/i 4" of the point of aim out to 300yds. Knowing this and that youre shooting at ~300 yds you can just hold a smidgen high. ... Not knowing, you only hit 4" low.