TargetTalk

I received the following e-mail from a shooter and thought others might benefit from my response:

"I am getting back into international smallbore after about 13 years away and am discovering 2 things: equipment sure has advanced and, my eyeballs aren't what they once were. (The prescription Knoblochs help just so much.)

I experimented some with filters when they were in their infancy in the mid to late 70s. Results were mixed at best for a number of reasons. I see that among other things the filter hardware available looks much more thought out and robust. Would you be willing to offer a few comments on your experience in applying filters to your advantage, which ones help and where?"

First thing I'd say is that if you don't have a bloop tube you probably need one. Not necessarily mine, but some sight radius extension would benefit your aging eyes.

First of all I like my Centra 1.8 Twin rear iris. It has two rows of filters, but I use only one of them. The 1.8 series iris has an opening range of .8mm-1.8mm. The other Centra iris series has an opening range of .5mm-3.0mm. To me it is much easier to fine tune the 1.8 iris opening.

When using filters, I have discovered that certain colors help in certain lighting conditions. This may not give the same result for everyone, so please experiment. In low light conditions I use the yellow filter. For very bright light on the target I use the orange (blue-blocker) filter. For less direct light on the target but still bright out I use the darker yellow filter. When the light is coming from behind the target and it is very backlit (the Ft. Benning range faces SouthWest), I use a green filter. The reason I use any filter is to increase contrast so the bullsye and front sight are sharper and easier to align.

I use the iris opening to also get the front sight/target into better focus with a minimum amount of eye strain.

Like I said in an earlier subject, I use both the filters and iris as a team. Back in the "olden days" the OTC lighting used to suck bad. It was really dark in there. I would shoot with a yellow filter and my rear iris opened to about 1.35-1.4. In those days it was pretty rare for anyone to shoot really high prone scores there. I did better than most, and I think it was because I had my rear iris adjusted outside the "norm" that people were comfortable with. When I shot back-to-back 600's there in 2003, Wigger asked me what my iris was set at. I told him and he said that he had never opened one up that much...and that maybe he should have.

Hope this helps,
Eric U

The reason I use that particular model iris is that it is the only one that has those four colors I use and the .8-1.8mm iris. I could do without the extra filter wheel in there (and added expense), but they don't make one like that.

Eric U

In bright light conditions, it is always easy to tone it down with the various filter options available. But what to do in lower light conditions? While the yellow provides needed contrast, any colored filter will also further limit the available light that is present. So I have typically just used nothing. What I haven't considered was your suggestion to increase the iris opening to compensate for the light loss when using the yellow filter. Thanks for the idea and will look at that next time.

Dennis

Thanks for starting this discussion, a Question; the Range I shoot on has full light on the Targets in early morning very strong, I Have been using the Grey options on my Peep or lately using the Polaroid option with some success-any comments?

Martin.

Eric, do you ever use a polarized lens and what is your opinion on that? I only shoot outdoor prone and at Riverbend there is a lot of glare on the targets with the sun at our backs. I have to keep things pretty simple or else my brain fails from overload, so I'm only using the polarization filter on my Gehman 550 iris.
Also, I've tried a tube several times and never seem to shoot as well with it. It makes sense that a longer sight radius would be more accurate, but I don't seem to have gotten the benefit. I know some people are using tuners with their tubes which makes me want to jump to the conclusion that the clamp and tube affect accuracy to some degree.
What can you suggest about setting up with a tube and also how long should someone work with a tube to find out if it is a benefit or not. My results on the several occasions I have experimented with a tube were immediately disappointing so I didn't waste much time on it.

I tried some polarizers very early in my shooting career and always found them to be too dark. I haven't tried them again in over 20 years. Polarizers may be better now than they were then, but I haven't found many situations that that I wished for something more than filters and the iris. Also, a polarizer makes the iris unit a little longer (a lot longer with the old Anschutz units that I had). I didn't like my eye being that far back from the sight. I haven't taken a poll lately, but I don't know any shooters who use polarizers.

I've also tried just gray filters and that didn't do as much for me as the colors. As a matter of fact, the other unused filter wheel on my Centra 1.8 Twin rear iris are all shades of gray. I've tried them all. I think Centra's intent with that iris model is to use the color filters in conjunction with gray ones. I tried that but again it made things too dark for my liking. Everyone's eyes work differently with colors. There is no reason why someone may be able to shoot just fine with only gray...or maybe even with a polarizer.

I'm a big believer in using bloop tubes. I also am a big believer that sticking anything on the end of your barrel will affect how it shoots (I use a tuner). That being said, I have seen very few guns that shot worse with a tube on it than without one. However, if you have a lot of ammo that shoots great without a tube, it might not be your best ammo with one.

Yes, you should be able to aim more accurately with a tube than without one, but I believe the biggest benefit is to eyes that have a harder time focusing close the older you get. There are many world class prone shooters out there that shoot just fine without a longer sight radius. They just seem to be younger shooters. Extension tubes are way more prevalent world wide now than they were 10-15 years ago. For a long time it seemed that the only people who shot with them were Americans, or people shooting short-barreled Anschutz rifles with a tube that made it a normal sight radius.

It is possible that trying a tube when you aren't used to one changes the balance of your position enough that you just don't shoot as well. I like a lot of weight up front in prone. It helps me. It might have the opposite affect on you. When I went from a heavier tube to the one I shoot now, I had to add a weight to my rail to make my position behave the way I like.

There are things you can do to make a gun shoot less than optimally with a tube. The first thing I think of is torquing the clamping screws too tight. This puts a pretty big choke in the barrel right at the muzzle. A small choke (smaller diameter bore) can be beneficial in a .22, but a big choke can really hurt your accuracy. Not using a torque wrench to tighten clamp screws can lead to inconsistent results. If the end of the tube doesn't butt up perfectly with the muzzle of your barrel, you will get uneven gas escape at your muzzle which can negatively affect your accuracy. It can also exaggerate your recoil as it acts the opposite of normal barrel porting (that is not allowed in ISSF competition). If you notice smoke coming out of the back of your tube, your seal isn't good enough. The last thing I can think of is not cleaning your tube bore. Over time the carbon will build up and make a rough surface on the interior of the tube that can possibly cause uneven gas flow. That can affect accuracy. Also, if you let the carbon build up on the interior of your tube too long it will be much harder to remove later.

More info that you probably wanted, but hopefully this helps someone.

Eric U

Eric,

Thanks for sharing your insight on filters and extension tubes. Touching on the filters first I had tinkered with them at one time but always found the results erratic. Probably the best results I had was working with a polarizer, this was one of those units that screwed into the front side of the rear sight. On a bright day you could adjust it and improve contrast but if the sun went behind a cloud it got too dark and unscrewing it in the middle of a string would change the zero and cost points. I am not so sure that the filter glass was perfectly perpendicular to the line of sight.

These days I shoot without any filters but as age takes its toll on my eyes I am willing to try anything to get that fuzzy grey ball out there to turn crisp and black again.

I have noticed that Centra has all kinds of sights and sighting accessories, it is nice to have a few pointers as I think I could go broke trying them all attempting to find the right combination. Do you have any thoughts on colored rear irises. In my kit I have a few simple Gehmann irises and I also have one Anschutz iris that is a burnt orange color. On most days and most lighting when you are up tight on the rear sight the burnt orange has a grey appearance. However I have never been able to decide if I really like or don't like the burnt orange compared to the traditional black. I see now that there are other colors out there too. So, what do you think about the rainbow in irises?

With regard to the bloop tubes, I agree with you, the barrel has certain vibrations and you have to be careful what you do that might affect them, hence even torque and seal are paramount. Several years ago I did a computer study modeling the pressure wave that forms ahead of the bullet as it accelerates down the barrel. While there were no conclusions to show exactly how a barrel should be made it did point out that there are many interesting things happening in the air the preceeds the bullet out of the barrel. Best not to have it upset or uneven.

I do enjoy reading your comments.

'Dude

I'm assuming you are talking about the "exchangeable color outer rings". I haven't tried any colored rear iris outer rings except for black so I don't have an opinion on them. Someone even makes a mirror assembly that goes into the rear iris. The theory is that you can "see" if your eyeball is centered. I haven't tried that either. I'm not sure my eye could focus close enough to get meaningful feedback.

Eric U

Regarding the use of polarisers, I have found them to be good at reducing the effects of mirage. I use a Gehmann iris with twin polarisers built-in so adding a polariser is no different to adding a colour filter.

Wow! thanks for that thorough answer!

Just wanted to say, I enjoy reading Eric's posts as well =)

Eric, thank you for your comments. They are a big help. I wish there were more top-shooters who are willing to share info with us lesser shooters.

This is my experience with irisdisk/filter co;ors on a dark shooting range with brigh light on the target:

My club uses a open 50m range and in wintertime at club nights the range is totally dark with only the shootingstand lit by TL-tubes and the target in relation tot the range and shootingstand very brightly lit. We have done testing with combinations of colorfilters and clor of the irisdisk. We found that we had to open iris and frontinsert by aprox. 0.2mm to get a clear sightpicture. Also we had best results using a light orange or green filter in the iris with a blue colored irisdisk.
Our explanation is as follows:
When the range is dark, the pupil of the eye has a relative large diameter. The light from the target is very bright, causing the lightrayes to refract in the eye and depleting the fotosensors in the eye very rapadly from pigment (commenly known as the sightpicture is burned on the retina). The rods in the eye are most sensitive to blue/violet light (like when it gets dark at night and everything gets a blue appearence). Using a blue irisdisc will produce more light reflected into the eye than a black disc. More (blue) light activating the rods decreases the size of the pupil, making the sightpicture sharper. The cones in the eye are most sensitve to yellow to green light. The green filter dampens the bright light to a level and color that the cones are most sensitive to.
Thats why the combination of blue irisdisk and green filter gives the best sightpicture on dark ranges with brightly lit targets.

The Dutch oilcompanies that own oil/gas rigs on the north sea have done extensive studies on the best color of light that gives the best contrast for human eyes at night and at the same time does not distord the flying routes of birds traveling over the North Sea between Holland and the UK. There conclusion was that green light at low lighting levels gives best contrast for humans while at the same time birds are most sensitive to light containing blue and red.
The watercompany I currently work for has stations for producing potable (fresh drinking water) in the middle of nature reserves (dunes along the North Sea) Al lighting at these stations is currently changed from the normal reddish or yellow colored lights to green lights.

Perhaps this info can be of interst for you all. If anyone wants to experiment with above mentioned irisdisc/filter color combinations and reports back, I would be very pleased.

Thanks,
Albert B
(The Netherlands)

Someone even makes a mirror assembly that goes into the rear iris. The theory is that you can "see" if your eyeball is centered. I haven't tried that either. I'm not sure my eye could focus close enough to get meaningful feedback.

Eric U

The mirror attachment is marketed by Centra as a training aid. From the looks of it in their sales brouchures it is a convex mirror. I have something similar in my medicine cabinet, a small 2" convex mirror, that can be used for inspecting the eyeball if you get the errant eyelash or if you wear them contact lens swimming around in the eye. It is a pretty amazing device, you can hold it 2 or 3 inches from the eye and even without glasses get a nicely focused magnified view of the eyeball.

I expect that is the deal with the Centra aid, it has convex curvature and they have the optics worked out so you can see the eye clearly at common eye reliefs. Training aid or not, don't know how well I would do staring back at myself while trying to squeeze off a shot.

'Dude

Eric,

Something that helps my aging eyes (I'm 52) is the use of a polarizer unit that screws in front of your rear sight. I take one of the two filters off because even at the brightest setting it is too dark for me.

An added benefit from such a tube (even without filters) is that it reduces the incoming beam of light to parallel light rays, effectively reducing scattered light bouncing off the edges of your rear sight. I believe it increases the contrast.

Anyway, its worth a try, you might like it.

As for the front sight aperture, I never play with it as I feel it is really critical to get consistent results when shading. A lot of training goes into being proficient at shading and changing aperture size makes an accurate assessment of shot displacement more difficult.

Hope to see you in Rio,

Gale Stewart
Quebec City, QC
CANADA

In the OP Eric U noted

When the light is coming from behind the target and it is very backlit (the Ft. Benning range faces SouthWest), I use a green filter. The reason I use any filter is to increase contrast so the bullseye and front sight are sharper and easier to align.

This past Sunday I fired my first match in... quite some time... The range faced northeast and used what I call "skeleton frames". There was a period before the sun came around where not only were the targets backlit but there were shadows from the wooden pieces of the target frame being cast on the back of the target as well. For part of 2nd 20 shot string the shadow was cutting through the bulls on the left side of the target. Fun times!!!

Not sure if any amount of filtering, green or otherwise, would help but does anyone have thoughts on how to work with such uneven lighting?

Cheers,
'Dude

Try using double backers. You may have to place one of the backers higher depending on the angle of the sun. Takes care of the problem.

Dennis