Long range airgun shooting

[Harry's Lad]

And while you're here, why bother with "flight time in a vacuum", if the pellet is at a constant velocity due to no wind resistance why not just incorporate muzzle velocity into the equation ? I think "flight time in a vacuum" is a red herring myself.

Did you look at the link that I posted? I thought that the physics/dynamics were described rather well.

The flight-time-in-a-vacuum is, in itself, irrelevant. What is important is the ‘delay’ (caused by the ballistic drag) of the pellet reaching the target. In a vacuum (or if the BC were infinite) then there would be no drag (and hence no deflection).

The sums work out like this :

Wind drift [Feet] = (s * sin(a)) * (t - (v/r)) … where:

t [seconds] = time of flight = 24000 * BC * (Exp(r / (8000 * BC)) - 1) / v
s = wind speed [in Ft/s]
a = angle of wind off trajectory path [degrees]
v = muzzle velocity [in Ft/s]
r = range [in Feet]

Note that the (v/r) term is the flight-time-in-a-vacuum so that (t – (v/r)) is equal to the ‘delay’ caused by drag. If the wind were at 90 degrees to the trajectory then (s * sin(a)) reduces to the windspeed since sin(90deg)=1

Dave

[Born Again]

Did you look at the link that I posted? I thought that the physics/dynamics were described rather well.

The flight-time-in-a-vacuum is, in itself, irrelevant. What is important is the ‘delay’ (caused by the ballistic drag) of the pellet reaching the target. In a vacuum (or if the BC were infinite) then there would be no drag (and hence no deflection).

The sums work out like this :

Wind drift [Feet] = (s * sin(a)) * (t - (v/r)) … where:

t [seconds] = time of flight = 24000 * BC * (Exp(r / (8000 * BC)) - 1) / v
s = wind speed [in Ft/s]
a = angle of wind off trajectory path [degrees]
v = muzzle velocity [in Ft/s]
r = range [in Feet]

Note that the (v/r) term is the flight-time-in-a-vacuum so that (t – (v/r)) is equal to the ‘delay’ caused by drag. If the wind were at 90 degrees to the trajectory then (s * sin(a)) reduces to the windspeed since sin(90deg)=1

Dave

That's just what I thought ( ).

Actually, on second glance, that's not nearly as complicated as it looks. I'll have a better look tomorrow when I'm not full of red wine.

Thanks, and any more formulae welcomed.

[Woodie]

We had another bash it yesterday, shooting out to 100 metres. Same setup as before, 5 shots per group at 18 ft.lbs.

Results – I achieved groups between 2 -4.1 inches. A friend of mine tried it on my rifle and was achieving a consistent group of 2-2.3 inches with my rifle.How embarrasing
This leads to conclude that it is down to the shooters ability, because I could not get a consistent group at all yesterday and he did.

We are trying to get our hands on a 27 ft.lbs to see what results we can achieve. And will keep you posted.

[Harry's Lad]

Those of us of a certain age will remember when the four-minute mile was thought to be the very limit of human endeavour - 'impossible' they cried! Then, shortly after Roger Bannister achieved the ‘impossible’, a whole raft of athletes did it. Within ten years, the four minute mile equivalent was essential before a athlete could taken seriously. I reckon it’ll be like that with sub MoA groups at 100 and 150 yards – provided, of course, that that nice Gordon Blair (Tony Brown? ... whatever) and the rest of the knee-jerkers will let us keep our airguns long enough.

Better get practicing …

Dave

[baz]

Heres a pic of the Pepsi bottle cap I shot several years ago with Career, 8 Bismags at measured 100yds, using a sandbag rest on bonnet of motor, the cap was trapped behind a bit of wire on a post

[Terry D]

Heres a pic of the Pepsi bottle cap I shot several years ago ...

Sez you.

Eh?

[rusham]

Did you look at the link that I posted? I thought that the physics/dynamics were described rather well.

The flight-time-in-a-vacuum is, in itself, irrelevant. What is important is the ‘delay’ (caused by the ballistic drag) of the pellet reaching the target. In a vacuum (or if the BC were infinite) then there would be no drag (and hence no deflection).

The sums work out like this :

Wind drift [Feet] = (s * sin(a)) * (t - (v/r)) … where:

t [seconds] = time of flight = 24000 * BC * (Exp(r / (8000 * BC)) - 1) / v
s = wind speed [in Ft/s]
a = angle of wind off trajectory path [degrees]
v = muzzle velocity [in Ft/s]
r = range [in Feet]

Note that the (v/r) term is the flight-time-in-a-vacuum so that (t – (v/r)) is equal to the ‘delay’ caused by drag. If the wind were at 90 degrees to the trajectory then (s * sin(a)) reduces to the windspeed since sin(90deg)=1

Dave

Very good, it all becomes clear!!!!

(Eye's become glazed, mouth slightly open, pen held to side of nose to try and show that he is listening, but in reality, the student is completely lost and hasn't the inclination to ask the lecturer to "repeat that bit again please")

[RichardH]

Heres a pic of the Pepsi bottle cap I shot several years ago with Career, 8 Bismags at measured 100yds, using a sandbag rest on bonnet of motor, the cap was trapped behind a bit of wire on a post

How did the other two holes get into it

[baz]

As I expected, and why I didnt put pic on the original thread

It was a concrete post that it was attatched to and by the time my mate (who also had identical Career) shot a couple of mags worth at a wine bottle cork in same place there was quite a bit of concrete missing

Admittedly it was an old post and a bit crumbly to start with but still not bad for an airgun

I remember chronoing the rifle in front of Terry Le Chem when TD brought him down a few years back I think it was doing 1030fps with Bismags

[RichardH]

As I expected, and why I didnt put pic on the original thread

It was a concrete post that it was attatched to and by the time my mate (who also had identical Career) shot a couple of mags worth at a wine bottle cork in same place there was quite a bit of concrete missing

Admittedly it was an old post and a bit crumbly to start with but still not bad for an airgun

I remember chronoing the rifle in front of Terry Le Chem when TD brought him down a few years back I think it was doing 1030fps with Bismags

I saw a bloke zero a .222 on a bit of board against one of those, just the reinforcing wire left

Richard

[Harry's Lad]

Very good, it all becomes clear!!!!

(Eye's become glazed, mouth slightly open, pen held to side of nose to try and show that he is listening, but in reality, the student is completely lost and hasn't the inclination to ask the lecturer to "repeat that bit again please")

The link referred to earlier here makes it a lot clearer.

HTH
Dave

[rusham]

The link referred to earlier here makes it a lot clearer.

HTH
Dave

Thanks Dave, quite interesting. I will admit that I do not take a scientific approach to my shooting and prefer to keep "things simple", but an interesting article non the less.

[Marko]

The link referred to earlier here makes it a lot clearer.

HTH
Dave

I think I'll read that on any other day bar a Friday, especially in the afternoon!

Just looking at it made me yawn.

Night night.

Mar...zzzzzzzzz

[Woodie]

maybe a silly question, but isn't the air thinner at night? (less resistance), just before sun down?

Are you likely to get better groups long range without a silencer?

[Woodie]

http://bsaog.co.uk/forum/index.php?topic=272.0