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Scope elevation question

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Hi

I have a problem and wondered if anyone can help.

I have my gong set out at 1000 mtrs, this has been a long awaited affair, but finally got round to it, perfect morning, kestrel set up and dialling in but ran out of elevation, bullocks!!!!

Right I am no expert thought I could rezero but tried to bore sight it with the elevation set to its lowest point but ret about 1 foot above target, had to do one complete elevation to drop cross hairs onto target at 25 yards. So what am I doing wrong, I want to get the scope zeroed on its first elevation.

Rifle. 260 AI AT 

Scope 5-25X56 schmidt and bender PM2 pf4

 

Any help?

Cheers 

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Have you got an inclined rail on the gun? 

If not a 20moa rail may help

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1 minute ago, furrybean said:

Have you got an inclined rail on the gun? 

If not a 20moa rail may help

I was given the advice of  a 0moa would give plenty it's a spuhr, I have a feeling this advice was inaccurate?

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Hello Raw

The advice you were given for the rail was correct. 

On a .260 you would need approx. 30MOA to reach 1000m. Your scope of choice has over 90MOA of adjustment meaning that on a flat rail (even after accounting for drop to zero at 100) you would have over 40MOA of available elevation, more than enough.

I think it is more likely that the scope is not set up properly.

Do you have a solid 100M zero?

Once you have your zero did you swing the turrets (unscrew the grub screws on the elevation turret and turn the turret to zero)?

Let me know if you still have problems but I doubt it is the scope that's the issue.

 

Ewen

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5 minutes ago, Deserttech Europe said:

Hello Raw

The advice you were given for the rail was correct. 

On a .260 you would need approx. 30MOA to reach 1000m. Your scope of choice has over 90MOA of adjustment meaning that on a flat rail (even after accounting for drop to zero at 100) you would have over 40MOA of available elevation, more than enough.

I think it is more likely that the scope is not set up properly.

Do you have a solid 100M zero?

Once you have your zero did you swing the turrets (unscrew the grub screws on the elevation turret and turn the turret to zero)?

Let me know if you still have problems but I doubt it is the scope that's the issue.

 

Ewen

Hi,

 

Yes have a solid 100 mtr zero and undid the grub screws and set the cap to zero but think to get the zero I had used one complete turn?!

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As far as I can see (from a quick look at the Optics Warehouse website), that model of scope has 65 MOA of elevation adjustment. So with a 0MOA rail, you have 32.5 MOA of elevation to play with.

Using my 6.5 load (142SMK @ 2700fps), from a 100yard zero I need 32 MOA of elevation to get on target at 1000 yards. So that's why you're running out of adjustment. You need a 20MOA rail. OR a scope with more elevation adjustment - 100MOA would be a safe bet. 

Triffid 

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Sorry, cross post.

Obviously there is a discrepancy from what Ewen knows about the elevation adjustment of the scope (90MOA) and what I saw on Optics Warehouse website (65MOA).

Triffid

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Hi Triffid, that is the elevation available on the turret (within the double turn) there is actually greater internal adjustment.

Their description is very confusing and I have even seen S&B staff give the wrong information to customers.

 

Ewen

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Your AT has a 20 MO rail built-in so the 0 MOA Spuhr Mount is correct. 

If you’ve got a good zero at 100 then you need to correctly re-set your scope to zero. You must be doing something wrong with the re-set because the rifle/scope/mount all work together well. 

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+1 on what TJC said and the comments from the other guys.

My AT has 20 minutes in the rail as standard so you should by rights be fine and the Spur mount would be the correct mount.

Go back to the start and take the sighting process step by step and you will be fine.

Regards

 

Reecy

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Thanks for the feedback folks, I sussed the scope out and was able to re-set it and now it makes sense, so thanks!

Was able then to crack on with the gong set on the farmland I was shooting on, I was using both the kestrel 4500 and the strelok (not decided which I will keep and which I will move on) today was the test, I must of fired around 15 shots non on the 30" gone so a little annoyed. On further inspection I noticed that all shots were around 3 ft high and 2.5 ft to the right (no wind). Up to 800 both kestrel and strelok were bang on, so what's happened? I am not a target shooter by trade, just trying to learn.

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That's 36" high in 200m, that's an 18 moa error!!

To be "bang on" at 800 but high at 1000 suggests a gross sighting adjustment error. The elevation suggests quite an error in down-range velocity: check the BC for your bullet and the settings in Strelok. Wind readings with your Kestrel are likely only relevant to where you're standing and not down-range so don't get side-tracked by windage errors, get your elevation right first.

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28 minutes ago, Popsbengo said:

That's 36" high in 200m, that's an 18 moa error!!

The error occurred at 1000, the 'step distance' from the previous range (800) doesn't determine the angular error, the new range does - so only  3.6 off expected POI.  :):)

 

 

Cold today....A problem beyond 800m.

Hmm:

RAW, at what range do your programs tell you your bullets were transitioning to subsonic flight at today's temp?  

(Edit to add: For a bit more precision, also reduce your input mv by 3fps for every degree colder it was today, compared to when you chrono'd your load)

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Yep, I agree the error is +3.6moa from the firing line, I was (clumsily) suggesting that to be on at 800 but high at 1000 was a gross error and unlikely to be weather (local vacuum😂)

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16 minutes ago, Popsbengo said:

Yep, I agree the error is +3.6moa from the firing line, I was (clumsily) suggesting that to be on at 800 but high at 1000 was a gross error and unlikely to be weather (local vacuum😂)

I'd be inclined to agree, most of these odd outcomes have simple, rather than complex causes.  My money is almost always on inconsistent position and hold from occasion to occasion.

That said, as in my post above, it was cold today.  No idea what round was in use, but if it's a pedestrian 308, transition will have been occurring not far  'after 800m'....and that can cause the wheels to fall off beyond that distance  in a number of ways.

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It's a 260Rem I think so pretty slippy. Also the zero was set with the same conditions (?) If the current weather is affecting calculation I'd expect an error causing low shots due to increased air density (cold, humid) however RAW is reporting 3.6moa high shots at 1000 so significantly less drop than calculated.

I suspect difficulty in adjusting the elevation turret correctly given earlier difficulties.

 

 

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43 minutes ago, Popsbengo said:

It's a 260Rem I think so pretty slippy. Also the zero was set with the same conditions (?) If the current weather is affecting calculation I'd expect an error causing low shots due to increased air density (cold, humid) however RAW is reporting 3.6moa high shots at 1000 so significantly less drop than calculated.

I suspect difficulty in adjusting the elevation turret correctly given earlier difficulties.

 

 

Yes. 260 

I did check the temp, I inputted 6'degrees, but kestrel was sat on bonnet of truck and that may of warmed it up, it did feel cooler.

 

I did shoot it at 800 a few weeks ago, and played with turrets slightly which resulted in some adjustments :(

yes should of been prone.

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1 hour ago, Popsbengo said:

It's a 260Rem I think so pretty slippy. Also the zero was set with the same conditions (?) If the current weather is affecting calculation I'd expect an error causing low shots due to increased air density (cold, humid) however RAW is reporting 3.6moa high shots at 1000 so significantly less drop than calculated.

I suspect difficulty in adjusting the elevation turret correctly given earlier difficulties.

 

 

Pops, yes, I agree, probably the simple cause.

If you want to increase your ballistic nerditry ( 😊 )

Increased humidity decreases air density. Counter intuitive, but it does.

'Cold' per se, will not be the primary determinant of air density  - station pressure will.  Eg   -20 on top of Everest vs -20 in Resolute Bay.

The effect to which I'm referring is the randomness, or disruption, caused when bullets transition from supersonic to subsonic flight.  In terms of projectile flight,  the effect is a 'randomizer' - up, down, anywhere, and will be accompanied by a deterioration in group size.    The primary determinant for the speed of sound is temp. Pressure is, for practical purposes irrelevant to determining the speed of sound.

I'd wager that today, with a temp induced mv drop, as well as a temp induced reduced speed of sound, the bullets were transitioning after 800m but before 1000m.

- and, if 'finger trouble' of any sort can be ruled out, decreased range to transition may well be, given the cold snap, an effect not often considered or seen - but very real and noticeable when it happens :)

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It sounds like you have set to zero on the second turn . Is the yellow showing in the turret window?

If so, you need to rewind the turret back to it's first turn when you loosen the screw and set to Zero, otherwise you will run out of elevation as you have done.

Don't ask me how I know

 

 

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2 hours ago, Roy W said:

It sounds like you have set to zero on the second turn . Is the yellow showing in the turret window?

If so, you need to rewind the turret back to it's first turn when you loosen the screw and set to Zero, otherwise you will run out of elevation as you have done.

Don't ask me how I know

 

 

Yep, that's exactly what I had done.

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3 hours ago, brown dog said:

Pops, yes, I agree, probably the simple cause.

If you want to increase your ballistic nerditry ( 😊 )

Increased humidity decreases air density. Counter intuitive, but it does.

'Cold' per se, will not be the primary determinant of air density  - station pressure will.  Eg   -20 on top of Everest vs -20 in Resolute Bay.

The effect to which I'm referring is the randomness, or disruption, caused when bullets transition from supersonic to subsonic flight.  In terms of projectile flight,  the effect is a 'randomizer' - up, down, anywhere, and will be accompanied by a deterioration in group size.    The primary determinant for the speed of sound is temp. Pressure is, for practical purposes irrelevant to determining the speed of sound.

I'd wager that today, with a temp induced mv drop, as well as a temp induced reduced speed of sound, the bullets were transitioning after 800m but before 1000m.

- and, if 'finger trouble' of any sort can be ruled out, decreased range to transition may well be, given the cold snap, an effect not often considered or seen - but very real and noticeable when it happens

Humidity reduces air density - well every day's a school day and I've learnt something useful, Cheers Ears :)

Finger trouble is identified !

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8 hours ago, Popsbengo said:

Finger trouble is identified !

Yup; not experienced 'zeroing on the 2nd turn'.    - I can see that accounting for the 'can't zero before elevation reaching end-stops' problem  - good spot Roy! - but I'm not clear how it subsequently accounts for 'zero achieved and all fine to 800, then wheels fall off'.   

Presumably, the zero issue was addressed successfully prior to the long range session (or else, how was it shot?)

Two separate issues?

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35 minutes ago, brown dog said:

Yup; not experienced 'zeroing on the 2nd turn'.    - I can see that accounting for the 'can't zero before elevation reaching end-stops' problem  - good spot Roy! - but I'm not clear how it subsequently accounts for 'zero achieved and all fine to 800, then wheels fall off'.   

Presumably, the zero issue was addressed successfully prior to the long range session (or else, how was it shot?)

Two separate issues?

Two separate sessions, on the 1000 session everything set up after the long walk carrying gongs, dialling in then realised not enough clicks available hence original post.

Also checked my data I wrote in my book 80 clicks for 800 which was spot on, I typed it last night and it said 84, so something in my inputted data has changed, don't think it is the rifle.

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2 hours ago, RAW said:

lso checked my data I wrote in my book 80 clicks for 800 which was spot on, I typed it last night and it said 84, so something in my inputted data has changed, don't think it is the rifle.

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?

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