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Scope elevation question

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1 hour ago, old_n07 said:

From what was posted on SD he's shooting 139gr Scenars @ 2709 fps

Thanks ☺

Need to know the temp that was fired at etc

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8 hours ago, brown dog said:

A 4 click change at 800 is well within tolerance - a 15degC temp change to inputs and a small pressure change would easily, and sensibly, cause that.

What bullet are you using? And weight?

What mv (and recorded at what temp)? 

Zeroed at precisely what distance?  And at what temp and pressure? Smack on, or off a bit?

What were the temp and pressure on the 'wheels fell off at 1000m'  day?

They were 139 scenars

MV 2709 zero at 15 degrees 

On the day 6 degrees, pressure (did not log this)

Zeroed at 100 mtrs

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14 hours ago, RAW said:

They were 139 scenars

MV 2709 zero at 15 degrees 

On the day 6 degrees, pressure (did not log this)

Zeroed at 100 mtrs

Some fag packet maths:

At 6 degC, mv reduced to approx 2686fps

Speed of sound at 6 deg C 1099fps

So if the air pressure was 1000mb, your rounds were firmly subsonic at approx 1100m.

If the pressure was 1100mb, they were subsonic at 1000m. (I'm sitting typing this at 1043mb)

Depending on how long before 1000m your bullets experienced transonic disturbance ,  or if the temp dipped further, or the pressure crept up a bit, or your ammo was a smidge slower you're definitely in the parish for seeing a transonic effect on the target at 1000m.

...and that, depending on bullet and conditions can make everything 'fine' at shorter range, and then suddenly, as you reach further out on a cold day, the wheels  suddenly fall off for no obviously apparent reason......

 

Once you're aware of this sort of stuff, there's no need to tear kit apart or doubt inputs when bullets go 'odd' way out there on a cold day,  it's just a matter of recognising the physical limits of the game when/if you bump up against them😊😊

 

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2 hours ago, brown dog said:

Some fag packet maths:

At 6 degC, mv reduced to approx 2686fps

Speed of sound at 6 deg C 1099fps

So if the air pressure was 1000mb, your rounds were firmly subsonic at approx 1100m.

If the pressure was 1100mb, they were subsonic at 1000m. (I'm sitting typing this at 1043mb)

Depending on how long before 1000m your bullets experienced transonic disturbance ,  or if the temp dipped further, or the pressure crept up a bit, or your ammo was a smidge slower you're definitely in the parish for seeing a transonic effect on the target at 1000m.

...and that, depending on bullet and conditions can make everything 'fine' at shorter range, and then suddenly, as you reach further out on a cold day, the wheels  suddenly fall off for no obviously apparent reason......

 

Once you're aware of this sort of stuff, there's no need to tear kit apart or doubt inputs when bullets go 'odd' way out there on a cold day,  it's just a matter of recognising the physical limits of the game when/if you bump up against them😊😊

 

Thankyou for taking the time, appreciate it, off back out in abit at less range just for a confidence session out to 450 and get to grips with this kestrel.

Thanks again 

Richie 

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