trajectory question

[Guest]

Archived from groups: uk.rec.shooting.game (More info?)

I have set my sights over about 30 yards with my [max power] air rifle being
held horizontally.

Sorted.

I presume that during the flight the pellet drops, which is why I must aim
slightly higher if the distance to the target is greater than 30 yards.

But what happens when I aim at an elevation of, say, 45 degrees
(crow/squirrel in tree rather than on ground) - should I aim above or below
the target? Or even an elevation approaching 90 degrees ?

Assume the same 30 yard distance to the quarry - or does the effective range
of the gun diminish depreciably when aimed upwards ?

Problem is, of course, that there is no way of knowing either the direction
of the error or by how much one has missed when nothing falls out of the sky
!

StJohn

 

[john]

Archived from groups: uk.rec.shooting.game (More info?)

"StJohn" <stjohn@needtoknowbasisonly.fsworld.co.uk> wrote in
news:c9amrd$1j6$1@newsg2.svr.pol.co.uk:

> I have set my sights over about 30 yards with my [max power] air
> rifle being held horizontally.
>
> Sorted.

I doubt that you could do this as a 12 ft-lb airgun will require at
least some elevation, I know my rimfire does.

>
> I presume that during the flight the pellet drops, which is why I
> must aim slightly higher if the distance to the target is greater
> than 30 yards.

The flight path of the pellet will arc, so you’ll need to aim “high” for
close targets, low for mid range targets, on target for the zero range
and high for targets passed your zeroing range. The exact path of your
pellet can be calculated by two methods.
First you could measure the velocity of your pellet at the muzzle and
then at 50 yds, this information together with the pellets weight can be
inputted into a ballistics program which will give you an approximate
trajectory graph. The second method (which is the best) is to set up
targets at 5, 10, 15, 20, 25, 30, 35, 40, 45 and 50 yds and shoot dead
centre. You’ll find your pellet will be below the line of sight, rise
above the line of sight mid range and then fall below after your zero
range. You must remember that your line of sight is always straight but
the path of your pellet arcs alone this line, crossing it in two places.

>
> But what happens when I aim at an elevation of, say, 45 degrees
> (crow/squirrel in tree rather than on ground) - should I aim above or
> below the target? Or even an elevation approaching 90 degrees ?

You have less gravity acting upon your pellet and so the pellet will
strike higher than your measured trajectory graph.

>
> Assume the same 30 yard distance to the quarry - or does the
> effective range of the gun diminish depreciably when aimed upwards ?

No.

>
> Problem is, of course, that there is no way of knowing either the
> direction of the error or by how much one has missed when nothing
> falls out of the sky !

Put a target board up a tree and try a target at the bottom of a steep
hill.

John

 

[Guest]

Archived from groups: uk.rec.shooting.game (More info?)

"John" <Stalking*@britishlibrary.net> wrote in message
news:Xns94F8E1E818C45OEcopyremovedheaders@130.133.1.4...
> "StJohn" <stjohn@needtoknowbasisonly.fsworld.co.uk> wrote in
> news:c9amrd$1j6$1@newsg2.svr.pol.co.uk:
>
> > I have set my sights over about 30 yards with my [max power] air
> > rifle being held horizontally.
> >
> > Sorted.
>
> I doubt that you could do this as a 12 ft-lb airgun will require at
> least some elevation, I know my rimfire does.
>

Sorry - horizontal-ISH.

>
> >
> > But what happens when I aim at an elevation of, say, 45 degrees
> > (crow/squirrel in tree rather than on ground) - should I aim above or
> > below the target? Or even an elevation approaching 90 degrees ?
>
> You have less gravity acting upon your pellet and so the pellet will
> strike higher than your measured trajectory graph.

Ah-haaaa! - therefore, tending to aim low to compensate for the need to aim
high on an 'horizontal' plane ?

>
> >
> > Assume the same 30 yard distance to the quarry - or does the
> > effective range of the gun diminish depreciably when aimed upwards ?
>
> No.
>

Good.


> >
> > Problem is, of course, that there is no way of knowing either the
> > direction of the error or by how much one has missed when nothing
> > falls out of the sky !
>
> Put a target board up a tree and try a target at the bottom of a steep
> hill.
>


Thank you. Most useful suggestion - I'll try it.

StJohn

 

[john]

Archived from groups: uk.rec.shooting.game (More info?)

"StJohn" <stjohn@needtoknowbasisonly.fsworld.co.uk> wrote in
news:c9b71b$h9o$1@newsg1.svr.pol.co.uk:

>> You have less gravity acting upon your pellet and so the pellet will
>> strike higher than your measured trajectory graph.
>
> Ah-haaaa! - therefore, tending to aim low to compensate for the need
> to aim high on an 'horizontal' plane ?

Think of it in this way.
When you shoot a pellet horizontally (for want of a better explanation)
gravity pushes down on the pellet. If the pellet travels 30 yds, gravity
exerts a force in a uniform manner over the whole distance. Now if you
elevate your shot to say 80 degrees and 30 yds distance, the pellet will
have less gravity acting upon it. Because you zeroed your rifle for 30
yds horizontal, you have compensated for the gravity and so when
shooting upwards or downwards at a steep angle your shot goes high.


>> Put a target board up a tree and try a target at the bottom of a
>> steep hill.
>>
>
>
> Thank you. Most useful suggestion - I'll try it.

It’s always best to try theory and the best way is to shoot at paper.

John