Disregarding the old fashioned "walk the sight in" method; precision first strike at long range requires a starting point from which to launch your own shooting skills. This was my afternoon's work to establish such with a new mount set-up. ..
Precision long/ extreme range shooting requires much homework to be graded "A" before the rangefinder is pulled from where body warmth keeps it always at the same temperature. ...
It starts with precision sight installment and finishes with clicking a precision made sight to correct elevation after range finding - then it's over to the shooter.
Recently I have been spending more time with my much loved RWS/FX Excalibre .22 again. Part of the motivation has been that when that box from Sweden eventually does turn up in OZ with my FX Elite .25, it may also contain a Smooth Twist FX barrel Fredrik Axelson of FX has prepared to drop into the Excalibre for head to head comparison with the outstanding original LW barrel.
Up 'til now a SportsMatch one piece mount with inbuilt droop has enabled direct sight click zero to as far as 170 yards with the 1.0" Bushnell Elite 4-16X scope on this rifle. Now I have just installed a new SportsMatch elevation and windage adjustable one piece mount bought from old stock from Lewis Reinhold. It should ultimately allow for zeros to well beyond 200 yards ... So beginning at the beginning, here are the steps so far:
Installing the scope:
My method begins with having the reticule centred in the scope. This I accomplish using the method devised by J Bruse Aurand. It is much faster and precise than old "V" box methods. It can be done in about 10 seconds anywhere using a small mirror. If you are interested I shall streamline the method to a couple of sentences.
http://www.network54.com/Forum/419052/m ... use+Aurand
After preliminary installation I use Mike Nelson's method of ensuring the scope has it's axis aligned above the bore line axis: There are other methods but this is now the one I use:
http://www.network54.com/Forum/79537/th ... nment+tool
OK the scope is on the rifle and we haven't forgotten the reason we are doing this to kick start long range precision work.
Scope on the rifle. Note the tapered gap in the adjustable mount.
Now I always use the excellent Chairgun ballistic program which of course relies upon quality data input as all such programmes do..
The sight axis' height above the bore line is a critical part of that data. The most accurate method I know, to derive that data, is to measure it at the muzzle of the barrel. I use Steve Woodward's method (or a slight variation which is not important) and which he introduced some years ago. It is the only one of which I am aware will do this at the muzzle without an expensive collimator :
http://www.network54.com/Forum/79537/me ... iflescope-
Next step was to sight in at a close range 15 yd in this case. . With the new adjustable mount I wanted to eliminate internal lateral sight adjustments by only using the mount's windage adjustment. Then I will have eliminated some of the problems associated with perceived torsions between lateral and vertical turret mechanics. Thus I should have vertical adjustments still centred on the vertical plane when clicking to maximum ranges when the whole available scope elevation is utilized. So I maxed out the sight vertical adjustment to near it's bottom value. That is I wound it down as far as it would go then up a couple of clicks and bumped it a couple of times.
A few shots were taken at 15 yards and thankfully things paid off with only a very minor adjustment to the mount's lateral movement needed to bring the POI onto the vertical plumb line. But of course the elevation was a fair way off. ... Unfortunately the mount must come off the rifle to change the mount's vertical adjustment. This was done a few times until the POI was a tad 3/10th" below the POA.
Now the range was extended to 25 metres at which range I want the start zero.( The "one range only" zero ).
As all else had been precisely done, the first shots were right on POA as the pellet trajectory rose the extra 3/10th" from 15 yards.
Now came the test of scope, Chairgun program and homework so far. I was relying upon my previous pellet BC tests ( 0.032 ) and scope click / moa values measured years ago as 7.518 clicks per moa (nominal on the scope as 1/8 moa).
The aim was to near max out the scopes vertical adjustment at the mount's setting set for zero at 25 metres with the scope adjustment bottomed out. I have near nine full turns of scope adjustment at 48 clicks per turn which spans approx 57 moa .
Chairgun indicated that at 175 yards I needed 52.53 moa times 7.518 (actual clicks/moa)= +395 clicks to zero to 175 yards ( 8 full turns plus 11 clicks ). This should give a POI of 15.40 inches / 39.12 cm high at 25 metres.
How did it all come together: I located the target strip and shot one pellet at the POA with the 25 metre zero (28 yd actually) and you see the highest of the three pellet holes on the cross at the bottom of the target. I then elevated the sight from it's extreme lower limit by +395 clicks and shot pellet # 2. You see it near the top of the target. Then the sight was clicked down the 395 clicks, given a couple of bumps, and two more shots fired. They are the other two in the group at the POA.
How far apart are the test result PsOI? ... Well, the measurement difference is 15.55" !!! That is just 0.15" more than Chairgun's 15.40". The high shot, which would give a 175 yards zero, is just 0.15" left of the plumb line.
Obviously the scope has tracked well straight up and down through it's full turret excursion and arrived back to group to about 0.20 inches including shooter and rifle and pellet variability.
Shooting was done standing with front wrist rested on a high stand and rear elbow on the wall (standing post so to speak ). I am very familiar with this stance.
So far so good. This scope is about 8 years old and has been clicked up and down probably thousands of times now. It is still precise. It pays to get a quality scope for precision shooting especially at long ranges.
When I next get to the farm I shall find out how much extra vertical adjustment I have in the SportsMatch mount and so find just how far I can zero the scope with this mount on the Excalibre. There seems much more left in the mount ... perhaps enough to get me to 250+ yards. This rifle has shot many sub moa 100 yards 5 shot groups and a number of sub four inch five shot 200 yards groups in calm air ............ .......Kind regards, Yrrah.
