Range Report Tall target test accuracy

[pitdog85]

I'm not sure if shooting the tall target test is an accurate enough way to measure scope error when trying to get below 2%. I'd be interested to know if any members have done several tall target tests on the same scope on different days.

I think unless you are using a benchrest gun capable of shooting in the .1's every time there is too much error. I have done several on the same scope with results from .3% error to 2.4%. Sometimes I can shoot 3 shots in the .1's and others the group will form with .5moa of
Vertical. So you measure your tall target from centre of group to centre but it really depends how your group forms and if its only a .5moa group you can play with the numbers a bit to see how easily your results can change a % or 2.

In my case I could be anywhere from needing no correction factor up to allowing for 2% error which one is true??

I use a tape measure but even then this is not perfect and again if you play with some numbers and your distance is 99.5m or 100.5m instead of 100m your results are rubbish. I measure to the turret some people measure half way between turret and barrel
Adds Some more error in there?? I shoot first thing in the morning when doing this to avoid mirage however there can be slight error in parallax as well that can add to a small % error.

I believe this is better than nothing and will show if you have some serious error like beyond 5% but I'm not convinced that this can produce reliable results when getting below 2%. With shooter and group shape variables as well as measurement error I think the only true way to get the truth would be in laboratory conditions something possibly only scope manufactures have access too.

I think the method of bolting the scope down with some sort of device like some do and running the test without shooting is certainly a better method I don't have the equipment or facility to do this but even then distance measurement and non perfect parallax can still be adding small errors.

I realise the likes of litz in his video doesnt bother correcting scope factor when below 1% but would be interested to see others thoughts on testing the same scope on differnt days whilst shooting and re setting up and re measuring the target each time and shooting the test to see if they have also found this method to have too much noise.

 

[pitdog85]

No one else has done multiple tests with similar results?

 

[Deleted member 10043]

You got it. The solid based scope mount testing just the scope is the proper way.

 

[pitdog85]

You got it. The solid based scope mount testing just the scope is the proper way.

Yer man I wasted enough ammo and barrel life to work all this stuff out!!!! I think this might be why so many have issues with "truing" which is actually scope errors that they either don't know about or have the wrong corrections in their app based on a single tall target test they may have shot and are trusting those results 100%.

 

[just browsing]

You got it. There are a ton of variables that could lead to inconsistent results. The test is really a “gut check” to make sure your scope is within acceptable mechanical limits.

As you said, the vast majority of guys/guns are not going to outshoot a 1% difference.

 

[ShtrRdy]

The other aspect of performing a Tall Target Test is to see if the elevation turret moves the crosshair truly vertical.

 

[Racer88]

I ran the test twice (in the same day). I got the EXACT same results both times (to three decimal places).

 

[pitdog85]

I ran the test twice (in the same day). I got the EXACT same results both times (to three decimal places).

Your a better shot than me, for me to get those results from playing with numbers my groups would need to be in the .1s everytime with no vertical.

 

[Racer88]

Your a better shot than me, for me to get those results from playing with numbers my groups would need to be in the .1s everytime with no vertical.

Or... Got "lucky!"

 

[CoryT]

For class we use a laser boresight on a tall gloss white board with a fixed aiming point. Sandbag the rifle in place on the aim point and mark the laser, dial up, check the rifle is still on POA and mark the new laser position. Lather rinse repeat in the increments you like.

This has the advantage of requiring no ammo and no reliance on group size each time. I've found it to be perfectly repeatable if you pay attention to marking the laser position. I use the Site-Lite SL-500 green laser, it's daylight visible, along with 1" targ dots to mark the laser.

 

[pitdog85]

For class we use a laser boresight on a tall gloss white board with a fixed aiming point. Sandbag the rifle in place on the aim point and mark the laser, dial up, check the rifle is still on POA and mark the new laser position. Lather rinse repeat in the increments you like.

This has the advantage of requiring no ammo and no reliance on group size each time. I've found it to be perfectly repeatable if you pay attention to marking the laser position. I use the Site-Lite SL-500 green laser, it's daylight visible, along with 1" targ dots to mark the laser.

That sounds like a great idea Cory.

 

[bassmaster07]

This has been my issue too. I have wanted to shoot a tall target to confirm but just sooo many variables to control. Do not have metal 300 foot tape. Range finder error or error using 100 foot tape. Then factor in shooting error and round to round variables... it just goes on and on.

I guess the $300 dollar scope tool is nice but that is a good deal of ammo. Guess it is all about how sure you need to be.

 

[Nik H]

You got it. The solid based scope mount testing just the scope is the proper way.

This is what I do with the Badger base. Works great and I am glad to say repeatable