fwb dioptre's

[GB2017]

Morning All

have acquired a fwb 300s and am getting a fwb 601 soon, however having never shot with dioptre's before was wondering where would be the best place to go to get an overview of the varios parts, ehat does what and the like.

Also are all the fwb stuff interchangeable?

cheers all

[markvulture]

Years ago when I bought my 601 I used the high foresight and rear raising block from my 300su on the 601, no problem at all!!! If you are fairly serious about using them then get an adjustable iris for the rear sight and the same for the foresight. Gehmann seemed the best in the day, the one I got for the foresight had a bar in it you could adjust to make your cant more consistent. Enjoy the 601 I really do regret flogging mine!

[GB2017]

Years ago when I bought my 601 I used the high foresight and rear raising block from my 300su on the 601, no problem at all!!! If you are fairly serious about using them then get an adjustable iris for the rear sight and the same for the foresight. Gehmann seemed the best in the day, the one I got for the foresight had a bar in it you could adjust to make your cant more consistent. Enjoy the 601 I really do regret flogging mine!

thanks, i think i want to improve on the basic dioptre provided but not be extravagant. I like the idea of the foresight bar to help with cant, re the adjustable iris is that adjustable re the aperture or something else

[tim s]

What does what? In simple terms, the tiny peephole narrows your focus so the target and foresight almost appear in focus together. The turrets on the rearsight move the eyepiece so your point of Aim and point of Impact coincide: when the rear aperture moves you instinctively move the barrel so the sights are aligned.

The foresight tunnel houses the foresight proper, shading it from light. The foresight itself is a stamped metal or Perspex disc. Perspex foresights have a chamfer around a central hole, in the tunnel the chamfer appears as a floating black ring.

Centre the foresight in the rearsight, then centre the target and release the trigger.

If you want accessories, start with extra inserts for the foresight, in a range of sizes - both metal and Perspex. These govern the gap around the target, too small an aperture can cause aiming errors.

An adjustable eyepiece is useful, so you can compensate for ambient light. Some just adjust the inner aperture. Others have colour filters to make the target stand out more; yellow is useful indoors under fluorescent light. Some have polarisers too, these are useful outdoors to tone down very bright sunlight. For indoor only shooting a simple adjustable iris is good enough.

You can get eyepiece that have an adjustable focus lens: these do the same job as glasses, but aren't permitted in some competitions. Personally I find glasses (or a lens attached to the sight) simpler and easier to keep clean.

[GB2017]

What does what? In simple terms, the tiny peephole narrows your focus so the target and foresight almost appear in focus together. The turrets on the rearsight move the eyepiece so your point of Aim and point of Impact coincide: when the rear aperture moves you instinctively move the barrel so the sights are aligned.

The foresight tunnel houses the foresight proper, shading it from light. The foresight itself is a stamped metal or Perspex disc. Perspex foresights have a chamfer around a central hole, in the tunnel the chamfer appears as a floating black ring.

Centre the foresight in the rearsight, then centre the target and release the trigger.

If you want accessories, start with extra inserts for the foresight, in a range of sizes - both metal and Perspex. These govern the gap around the target, too small an aperture can cause aiming errors.

An adjustable eyepiece is useful, so you can compensate for ambient light. Some just adjust the inner aperture. Others have colour filters to make the target stand out more; yellow is useful indoors under fluorescent light. Some have polarisers too, these are useful outdoors to tone down very bright sunlight. For indoor only shooting a simple adjustable iris is good enough.

You can get eyepiece that have an adjustable focus lens: these do the same job as glasses, but aren't permitted in some competitions. Personally I find glasses (or a lens attached to the sight) simpler and easier to keep clean.

thank you for a very comprehensive overview

[tim s]

Not quite comprehensive enough, there are a few small points I forgot.

Eye relief - you want the rear aperture 1in-3in from your eye. A good start is 1.5in. Get help to do this, so you can find a good position for your cheek on the butt, and they move the rearsight into place.

The foresight tunnel should take up about 1/3rd of the rear aperture. As with the foresight, too tight a fit isn't good. Less eye relief makes for a brighter sight picture, and more room around the foresight, but you lose a little depth of focus. More eye relief increases depth of focus, but the sight picture is darker, too dark won't help. Eye relief is a bit of a compromise at first.

Shooting glasses help with this; a shooting specific prescription gives you a good sight picture (sharp foresight, less sharp but still clear target), with less input from the rearsight aperture. With glasses you can enjoy a good sight picture without needing a super small aperture.

[markvulture]

The adjustable foresight is also an iris so you can twist it and effectively change its diameter. Alongside the adjustable bar it was a very useful piece of kit.

[GB2017]

The adjustable foresight is also an iris so you can twist it and effectively change its diameter. Alongside the adjustable bar it was a very useful piece of kit.

had taken it all apart and wondered if it would allow focus, still cant establish exactly what the diameters are though, and finding concise documentation is a royal pita

[tim s]

had taken it all apart and wondered if it would allow focus, still cant establish exactly what the diameters are though, and finding concise documentation is a royal pita

The foresight doesn't really have any input on focus - that's all in the rear peep, or glasses.

We use a foresight ring because it gives a 360° reference against a post.

On a basic foresight iris the numbers are the diameter of the inner aperture in mm. For the 10m target, start somewhere over 4mm. You want enough space around the target that the foresight ring doesn't overlap it as you aim. That's the risk with a foresight that's too tight around the target.

Irises can also be used for 22rf shooting. Prone shooters mostly use a smaller aperture as the position is much less wobbly; 3.6-4.0mm is recommended for a regular Anschutz barrel.

Some irises also adjust the outer diameter of the ring too. Basic irises tend to get thicker as you reduce the aperture. Don't like this? Then tweak the outside so it's a constant thickness, or a proportionate thickness to the aperture. Dual adjustment irises tend to come as a tunnel.