TargetTalk

Thinking out loud, after seeing a photo of Harald Stenvaag at Dortmund yesterday with massive rear sight eye relief (about two inches by my estimate) is there any aiming gains or disadvantages having such a large amount?

In my own training last week (indoor at 25yds) reducing the distance between the rear sight and my eye really brightened up the sight picture and seemed to remove edge diffraction around the aperature. However my thoughts are the closer the rear sight is to the eye the harder it is to centrallise the sight picture, and especially head position after clicking the sights. Would pushing the rear sight out further foward allow gains in accracy and is there a sweet spot or is it all just personal preference? (Excluding the advantages of being able to see wind flags)

cheers

I think you listed most of the pros and cons comprehensively except to say it will need to be re-zero'd after shifting it forward or back.

Assuming we are talking about smallbore, I was always taught to bring the rear sight close to my eye; I had a pair of shooting frames and so I made sure the lens was nearly right up against it. One of the most common adjustments I do with junior shooters (and even some advanced) is to move the rear sight back closer to their eye. I have been told, and concur, that it makes front and rear sight alignment easier; the argument that you cannot center the front sight as easily in the rear sight is not something I agree with. If this was the case, then shooters would not use bloop tubes, as it makes the front sight smaller in your sight picture (although that is not their intended use). Personally, I believe that it allows you to see easier, and be more aware of your surroundings. I even moved my rear sight forward and back due to the requirements of my position.

-Zach

Stenvaag is also a 300m shooter. Perhaps he like the rearsight a little further forward to avoid being hit under recoil and he sets up his small bore the same so they are consistant?

A complete guess on my part!

Bryan,

2in isn't really that long. Find a copy of Pullum & Hannekrat, and you'll see US AMU shooters sporting eye reliefs double your 2in. At the other end of the spectrum, some Chinese shooters have won World Cup medals with almost no eye relief at all.

If you search this forum, you'll find posts by Ken Bowler a few years ago on aperture size and eye relief. His view was that with the correct lens for focal length, a tight aperture was less important. A larger/closer aperture brought more light, and larger central "sweet spot" away from the distortion of the edge.

You'd also get a wider down-range view with less eye relief.

What about Nazar Luginets also from ISAS this year? Seems to work for him at least. Best in qualification with 1180 and second after final.

Hi Bryan, since Tim invoked my name I thought I might update my thoughts on this subject.

Firstly, in my experience, eye relief depends on the ambient light level - shooting outdoors requires less eye relief than shooting indoors if you want to retain a consistent sight picture. I guess this is to do with the dilation of your pupil. You can see this when you are shooting on a dull day and the sun comes out - the apparent size of the peephole closes down.
I adopt the Heinz Renkimeyer idea that the foresight should be roughly in the centre third of the rear peephole - I.e. For an 18mm foresight you should be able to see 18mm to the left of the foresight and 18mm to the right of the foresight (I hope that's clear anyway).
Adjusting the size of the rear aperture doesn't change these proportions even though it might seem logical that it should.

Secondly, the size of the rear aperture is a trade off - a small aperture will increase depth of field but at a price. Older shooters like myself may develop "distortions" due to imperfections in our cornea or lens which become more problematic with a smaller peephole. A smaller area of cornea/lens is used while aiming and any imperfections will take up a larger percentage of that area. A larger peephole will reduce the perceived distortion as (hopefully) less of the area of the cornea/lens will be blighted by these imperfections and everything will be "averaged out" to some degree. I will frequently shift my head on the cheekpiece until I find the clearest image of the foresight (or the least imperfect section of cornea/lens). This seems to work fina as long as you remain within the "sweet spot" in the centre section of the peephole.

However, opening the rear iris also reduces the size of the optical sweet spot in the centre of the peephole where accurate aiming occurs so some care is needed. Increasing eye relief would make it easier to centre the foresight but the sweet spot would also shrink making gross errors more common if you get it wrong.
Opening the rearsight also reduces the depth of field so the target may appear more blurry BUT this is where having the right lens comes in.

Using a lens to put your relaxed gaze at double the distance to the foresight (the hyperfocal distance) will at east make the foresight and target equally blurry which offers some compensation for the loss of depth of field. This would require a lens which is +0.5 dioptres added to your distance prescription (as a rule of thumb).

I'm sure there are other compromises but that's my current thinking. I rarely use an aperture of less than 1.2mm and have had good results up to 1.6mm depending on conditions.
If I use a filter it would probably be a green one just to knock back a really harsh glare but I've found I aim best if the sight picture is slightly brighter than I find comfortable (if that makes sense).

YMMV.
Regards, Ken.

Eye relief is a lie.

Google Parallax suppression and prepare to have your mind blown.

Why do you say "Eye relief is a lie"? I've read that article, and I don't remember it saying anything about eye relief not impacting the sight picture or other variables, like target brightness.

marky-d

Maybe not a "lie" but eye placement behind the sight does not in turn hurt aiming accuracy.

Yes, but the paper is about misplacement from the "sight axis", whereas the eye relief question centers around position ON the axis.

I'm not trying to be an ass -- the paper is just a little 'dense' and people may not actually read or understand it.

cjon600 wrote:Eye relief is a lie.

Google Parallax suppression and prepare to have your mind blown.

Is that the paper using a Mini-14 clamped to a bench? A more realistic study, would have considered that this artificially aligns the barrel and foresight with the target.

In the real world, not centring the eye or foresight with the rear aperture produces poor shots. Why else would a well-fitting cheekpiece be important?

No worries. I totally get the statements. I was exactly in your shoes once too. I had the same argument. Until somebody proved to me that it was incorrect.

Try this: on a bench sight in your rifle like normal. Then take your eye behind the sight as high as you can while still being able to align the sights, and put the front sight at 12 oclock and shoot a 5-10 shot group. Repeat the process for 3, 6 and 9 oclock positions. As long as your "peep" is smaller than your eyeball iris, your groups will not change.

Ive tried it with with an airgun on electronic targets as well as with a scatt mounted on the rifle.. Its mind boggling!

That's the issue, If the rifle is properly, benched it won't move. How a benched rifle behaves is irrelevant for Position shooting, but how it behaves from the shoulder is.

With the rifle shouldered, there is the tendency to re-position the barrel/foresight. This is the issue. We know that groups don't move the alignment of the barrel doesn't change.

Of course, this is not true for open/pistol sights, where the target, front sight, and rear sight must be aligned to the shooter's eye. This is what had me confused for a long time! For a peep sight, the rear aperture and eye are in nearly the same place. The rear sight aperture overlaps your eye's pupil and by moving your eye you're just changing which part of the pupil the light goes through without affecting the rifle alignment. One should try to center the front sight on the rear peep to maintain consistent head position for repeatable shot response, but I don't think that centering is as critical as for aiming with open sights. Please see below an excellent parallax suppression article:

https://www.google.de/url?sa=t&rct=j&q= ... UrveUl3l9P

This is a bit counter-intuitive, but the simple experiment that cjon600 described clearly demonstrates that parallax doesn't produce significant aiming errors. Of course changing your eye/cheek position will change how the rifle recoils, which is a problem.

Best wishes,
John

John - I read the article on Parallax Suppression a few years ago and I think it's broadly correct BUT....

I think it only applies to the centre region of the peephole (which I've referred to as the "sweet spot". If you start looking through the outer portion of the rear aperture, the iris of your eye starts to occlude the peephole and although it still appears circular you start to lose light and get diffraction effects which make accurate aiming difficult.

However, as long as the rear aperture and your pupil completely coincide then an accurate sight picture should be produced on your retina - which does make head position less critical. I'm not obsessive about having the foresight PERFECTLY in the centre of the peephole - I look for the clearest image of the foresight (which sometimes appears slightly off centre...). Eyes are tricky little buggers.

Eye relief (the distance from eye to rearsight) is something different.

Regards,
K.

So, if parallax and eye relief aren't a big deal, why isn't everybody shooting 10.9's???
We all should be able to just look through the rear thingee and line up the front thingee on the target, right?!?!?

When I first started shooting M-16's in the Army, I shot how they taught me: nose up close to the charging handle and little eye relief.
I noticed that the sight picture didn't really didn't seem to matter because I could move my head/eye around as long as I kept the front sight post on the target, but that was after I was apparently getting an initial, super-quick, subconscious sight alignment.
Because I noticed that once I was "locked in" like this and let my sight picture drift, if I moved the gun butt to correct the bad sight picture rather than my head, I wasn't as accurate if I hit the target at all.

Then, after 9/11, we started the whole "train-as-you-fight" thing.
So, we started wearing body armor to the range in 2001.
Up until 2011, I was always issued a fixed stock M-16.
The combination of those two things forces you to slide your head further back from the rear sight if you're lazy, like I was.
(Even before 9/11, I had heard from a couple of better the division small arms trainers to put your cheek further back, but never I'd practiced it, so I embraced this, rather than fighting to get my eye closer to the rear sight like the rest of the Army.)
I noticed this really tightened the sight picture with a kinda "scoping" effect that made me think of what it must've been like to use one of those barrel length scopes from the late 1800's.
Although, I had always shot well, my scores really improved despite having to wear all the extra crap to the range.

gspell68 wrote:So, if parallax and eye relief aren't a big deal, why isn't everybody shooting 10.9's???
We all should be able to just look through the rear thingee and line up the front thingee on the target, right?!?!?

One of my exercises is to shoot with iron sights from a benchrest rig with SCATT attached to see how well you can aim - all other factors taken out of the equation.
I've seen people shoot a 10.8 average like this (on SCATT) - ammunition variation tends to become significant when judging results at the target. It's not a bad way to do batch testing though.