TargetTalk

I have been fortunate to acquire an immaculate Walther LGR.

It has original Walther rear diopter sight and what appears to be an Anschütz foresight tunnel attached to the dovetail. The foresight has a 0.5 diopter magnification lens so far as I can tell by the markings, which is on the rear side of the interchangeable element.

I have also got a Gehmann 550 polarising variable iris, which I have screwed into the rearsight in place of the Walther 'pinhole' iris. The tighter iris I feel better.

As I'm a hobbyist as opposed to a competitor, I'm shooting at 20m or 25 yards - simply as I have a range set up at that distance for my other rifle shooting. The LGR shoots very well - I can get a group of about 20-25mm at that range, wind-dependent, with wadcutters. If I shoot on my indoor 6m pistol range, the grouping is under 10mm. Remember I'm an amateur, and I confess I'm using a front rest...

I'm long-sighted.

Rearsight iris to foresight element is about 30" on the LGR.

My questions are:
1. Is the 0.5x foresight element advantageous to me? If not, why, and what should I use?
2. I'm curious about the Gehmann 560/561 'zone plate' (or 'fresnel') rear element. In theory might give me duality of target and foresight element sharpness? But would I need to lose the 0.5x foresight lens? Worth the bother or not? 560 presumably for my rifle? And open back up on iris possibly?
3. Any suggestions as to other foresight elements? Tints etc.?
4. What about foresight size? I have a range of circular ones, plus a few posts. Hard to buy it seems as they're 16mm.

Sorry if this is all a bit basic, but I'd like to make the very best of a gorgeous rifle. Thanks.

1) The +0.5 lens gives a focal distance of 2m; with a Smallbore Rifle this typically gives a slightly clearer target (and a clear foresight) with less eye strain. The focal length might be a little long for an air rifle, but not ridiculous.
2) The reports I've read suggest the 560/1 is fussy over eye relief and darkens the sight picture. Unless you can't get a good sight picture with a conventional lens, I would not bother.
3) It's worth trying different types of sight element (Perspex vs metal). Perspex elements give a less cluttered sight picture, but can fade in strong light, and don't have a horizontal reference. I like a clear element, but I use a yellow monocle lens. One British champion used/s a hot pink tinted element.
4) Size is important. Today a broader gap around the target seems to be recommended. The logic is that the inside edge of the foresight is distorted by refracted light; it's not a clean transition from black to white. Keeping this away from the target helps, as the gap is brighter and we can detect smaller variations in brightness (when the target is centred) better than the the physical gap. If the gap around the target is very tight, you can overlap the target with the foresight and not notice, because you mistake the halo of refracted light around the inside for a gap.

In terms of size at 25 yards a 3.6-4.0mm aperture suits a 33in sight radius (standard Smallbore) and a 2in diameter aiming mark. You could knock of 0.1-0.2mm for the 30in sight radius, and scale that up/down for a larger or smaller target.

That's really helpful Tim, thank you.

Your comment about a slightly larger element resonates with me - today I dd observe a degree of 'fuzziness' on the perimeter of the bull as it was pretty coincident with the ring. The more i concentrated the more they merged...!

I like the idea of perspex elements - just need to track down the right size as mine need to be 16mm dia, unless I invest in another foresight.