Is scope alignment the issue?

[cal_23]

Looking for some advice if possible?

I shot on Stickledown range at Bisley for the first time yesterday (900 yards). The required number of clicks dialled on my scope didn’t match my ballistics data which makes me think my scope alignment with my rifle isn’t correct. Would people concur with my understanding or is there something I’ve missed?

I shoot a Tikka Tac A1 in 6.5mm Creedmoor. I load my own bullets which have been giving me an average speed of 2626fps. When I put the data into Chairgun Elite ballistic app I get a correction of 7.7mils up and 0.2 right (note there was perhaps a max of 3 mph wind from the right).

To get on target from my first sighting round I needed to dial up 8.0 mils and left 0.5 mils (a difference of up 0.3 and left 0.7 from the app’s correction). Note: I’m using a Sightron SVIII 5-40x56 FFP scope.

I ended up with all but 1 shot in the V-bull in my last 10 shot group and despite being happy with my first attempt at that range, I’d like to be able to feel confident in being able to dial up different ranges from the off. Does this sound like a scope alignment issue?

Any advice would be welcomed.

 

[Reloader708]

I assume you mean do the clicks on my turrets match the actual value advertised?
Ladder test, loads of videos on YouTube of how to do it but it'll show up any anomalies.

 

[cal_23]

I assume you mean do the clicks on my turrets match the actual value advertised?
Ladder test, loads of videos on YouTube of how to do it but it'll show up any anomalies.

Thank you. Yep, I don’t think my cross hairs on my scope are perfectly aligned to the rifle. I need to do a box test to confirm.

 

[NP435]

The question is did you do the shooting and develop data based on results, or have you relied on data from some other source?

 

[VSS]

I don't think the clicks on a scope are ever exact, are they? Near enough as makes no difference when zeroing at 100 yards, but at longer ranges any anomalies will become apparent, perhaps?

 

[cal_23]

The question is did you do the shooting and develop data based on results, or have you relied on data from some other source?

Thank you. Yep, I’ve tried to source accurate info. The speeds have been taken using a Garmin Xero (standard deviation and extreme spreads consistently <10 fps for the load). The ballistic coefficients from Hornady (for eld-m 140gr) and the weather (temp and pressure) were taken from a kestrel. I’ve tried to cover all bases and I can’t explain the large difference, particularly the windage, which makes me think it’s the scope alignment.

I’ll be doing a box test next time for sure.

 

[hendrix's rifle]

Have you set your scope height correctly? Is your zero absolutely cock on at the chosen zero range? (I do mean absolutely cock on).
Did you consider that at the shooting position there was a 'max' 3mph wind but out over the 900 yards that likely altered?
Did you check any data first? Usually BC aren't 100 percent accurate and can be very much inflated by the manufacturer. I'd also use the hornady app as it gives you as close as possible with your velocity and their Doppler radar.

 

[jcampbellsmith]

File your plots, document what you did and go back and shoot again. Each time that you shoot, conditions will be different and you will learn something new.
Regards
JCS

 

[JTO]

Have you set your scope height correctly?

= my first thought.

 

[Jagged77]

Regarding windage, I know there are range flags but how do you know for absolute certainty that it was no more than 3mph. My point is what’s more likely, mis calibration / alignment of the scope or outdoor conditions having a more pronounced effect? Did you set all your atmospherics and height above sea level into your balistics calculator too (vs what they were when you zero’d)

 

[Smellydog]

"Is scope alignment the issue?"

Most probably.

It's an assumption that when a scope is fitted to an action the action is perfectly aligned with the bore.
Bore sight it with a centered scope, then you will have your answer.

 

[webley701]

"Is scope alignment the issue?"

Most probably.

It's an assumption that when a scope is fitted to an action the action is perfectly aligned with the bore.
Bore sight it with a centered scope, then you will have your answer.

A miss-aligned scope can result in using up part or all of the elevation or windage adjustment the scope allows to get the scope to zero but it doesn’t affect the required elevation adjustment from one distance to another.

That aside - assuming cal-23’s scope really was zeroed at 100 yards then requiring more elevation than calculated could be due to:

Scope height above bore not exactly the same as what’s been used in the ballistic calculator.
Bullet BC not as exactly advertised (very common).
Bullet BC varies with velocity - even if the maker gives these figures the velocity/BC bands are not exact modelling.
Scope adjustments don’t exactly match moa/mil (not uncommon when relatively large adjustments are required).
Rifle handling - slight difference in the way a rifle moves under recoil can affect point of impact & if the basic set-up is different in any way from that used to zero you can end up with an unexpectedly higher or lower point of impact.
The list isn’t exhaustive……

As regards wind, a constant wind along the length of Stickledown isn’t generally the case even if the flags don’t at first sight ‘seem’ to show any difference. You have to watch them like a hawk & observe other more natural indicators in light wind conditions. If someone hasn’t shot at 900 yards on a certain range it’s unlikely they’ll be judging the wind as precisely as they’d like (this is part of the enjoyable learning process).

 

[Smellydog]

but it doesn’t affect the required elevation adjustment from one distance to another.

Yes it does.

 

[Tarquin]

I doubt any ballistic app is exactly spot on. If 7.7 was predicted and you needed 8 I call that a win.
I use JBM ballistics - not an app - and most of that was developed by Bryan Litz.
However the windage variance could be an out of kilter scope.
IIRC 1 degree out is something like 20 inches at 1000 yds. (stand to be corrected - but you get the drift(!!) )
There are some natty tools that are cheap to buy and work well for scope fitting such as this one:

https://www.amazon.co.uk/RALSPEC-Gunsmith-Riflescope-Alignment-Leveling/dp/B0CLQNJHS1/ref=sr_1_18?crid=3ITJ2LHGYBI8T&dib=eyJ2IjoiMSJ9.PyKpf0dZ-b9C480A-aFp-lFdWHME6gjdbegtbEYKdVk5DtsXeYZB54mnOdMlMoD1N6FlrArTZI7VGJ8AOR0eDvpb-210GwxIbmCqAnROGkIBecP3yAu98gVGBvJ6wDWutiT0DyJjRKluu0P1XPcoHR3o2CH_VM9yf2bGOPx4v2rfdXAHtvX3iU1-sg6pt_bHhiuzgWrWdG9FttaxPmytxYpHFo2rQBkuryc6CWzkOwGWMOHM-bX-DZcUbFPNmJieObvtCYEbOUC2hNlQndsEsV3Gb4kHk-CU5XdW1kZRCLs.SA19yED3fSrkz3vllJUnC6JuKFFtMpj3jhYRrnpbyXc&dib_tag=se&keywords=scope+sight+tool&qid=1725871503&sprefix=scope+sight+tool%2Caps%2C277&sr=8-18

 

[Eddie P]

A canted rifle can account for windage issues too.

 

[C h r i s]

You actually believe the BC's as published by Hornady?! They are somewhat exaggerated,.it's all marketing BS. Reduce by 10 to 15% and you might be in the ball park.

 

[webley701]

Yes it does.

I beg to differ.

As an example - consider a rail with a 20 moa incline built in - here the scope doesn't at all align with the bore but when the scope is zeroed at (say) 100 yards the rise in elevation needed to get to from 100 yards to 900 yards is exactly the same as one mounted on a flat rail which is presumably aligned to the bore.

(What would be different in this example is when zeroed at 100 yards using the inclined rail the scope will be using the normally redundant bottom half of it’s adjustment travel - thus leaving a lot more of the total adjustment travel for elevation - hence the common use of inclined rails for longer distance shooting.)

A unintentionally miss-aligned scope can cause part or perhaps all of it’s adjustment range (windage or elevational) to be used to obtain zero - it doesn’t alter the amount of adjustment required from a zero at (say) 100 yards to any further distance.

 

[Smellydog]

I beg to differ.

As an example - consider a rail with a 20 moa incline built in - here the scope doesn't at all align with the bore but when the scope is zeroed at (say) 100 yards the rise in elevation needed to get to from 100 yards to 900 yards is exactly the same as one mounted on a flat rail which is presumably aligned to the bore.

(What would be different in this example is when zeroed at 100 yards using the inclined rail the scope will be using the normally redundant bottom half of it’s adjustment travel - thus leaving a lot more of the total adjustment travel for elevation - hence the common use of inclined rails for longer distance shooting.)

A unintentionally miss-aligned scope can cause part or perhaps all of it’s adjustment range (windage or elevational) to be used to obtain zero - it doesn’t alter the amount of adjustment required from a zero at (say) 100 yards to any further distance.

The inclined rail is causing the first cross over to come nearer to the muzzle. That extends the second cross over.
As trajectory is not linear so the adjustment at extended range will not be linear compared to an earlier second crossing point.

If data predicts say a +9" adjustment at 300yds for a parallel sight it will be less at 300yds with 20moa rail.
Because the mid range trajectory height has increased.

Many a sight is shimmed when for what ever reason, right or wrong, the user runs out of adjustment. Irrespective of adjustment the misaligned scope cannot get near the trajectory of the bullet.
Only once alignment is very close do the adjusters become of value.

Only the other week I zeroed a Hawke 22 subsonic Ret scope on Norma subsonic ammo which is slower than what the scope was developed with.
Adding some shim to incline the objective bell down brought the reticle values much closer to the slightly slower ammunition.
It does have an effect on the values.
Atb.

 

[kenbro]

I doubt any ballistic app is exactly spot on. If 7.7 was predicted and you needed 8 I call that a win.
I use JBM ballistics - not an app - and most of that was developed by Bryan Litz.
However the windage variance could be an out of kilter scope.
IIRC 1 degree out is something like 20 inches at 1000 yds. (stand to be corrected - but you get the drift(!!) )
There are some natty tools that are cheap to buy and work well for scope fitting such as this one:

https://www.amazon.co.uk/RALSPEC-Gunsmith-Riflescope-Alignment-Leveling/dp/B0CLQNJHS1/ref=sr_1_18?crid=3ITJ2LHGYBI8T&dib=eyJ2IjoiMSJ9.PyKpf0dZ-b9C480A-aFp-lFdWHME6gjdbegtbEYKdVk5DtsXeYZB54mnOdMlMoD1N6FlrArTZI7VGJ8AOR0eDvpb-210GwxIbmCqAnROGkIBecP3yAu98gVGBvJ6wDWutiT0DyJjRKluu0P1XPcoHR3o2CH_VM9yf2bGOPx4v2rfdXAHtvX3iU1-sg6pt_bHhiuzgWrWdG9FttaxPmytxYpHFo2rQBkuryc6CWzkOwGWMOHM-bX-DZcUbFPNmJieObvtCYEbOUC2hNlQndsEsV3Gb4kHk-CU5XdW1kZRCLs.SA19yED3fSrkz3vllJUnC6JuKFFtMpj3jhYRrnpbyXc&dib_tag=se&keywords=scope+sight+tool&qid=1725871503&sprefix=scope+sight+tool%2Caps%2C277&sr=8-18

1 degree of lat is 60 NM on earths surface.
The 1in 60 rule is handy when you’re flying.
KB.

 

[NP435]

One possibility is value of wind making changes, flags show this but swirls and thermal effect's change over long distance. One of the ranges I shot on at Camp Pendelton Ca was in a wide valley and the wind swirled back and forth east to west. Frustrating and quite a challenge. Good luck.