issues converting from 18 to 22mm sight tunnels

[btucker]

Finally figured out a 4mm riser on the rear sight gets me back to usable elevation range. Now my issue is very little air between rear sight tube and front sight tube. Hard to center. So it's moving my head further into the rear iris to see more air around the tube. I did order a 10" bloop tube and will move the fore sight further out , that should help. My rear iris opens to 3.0, I like it and don't want to change that. Starting to think it's not worth moving to 22mm.

[Tim S]

Out of interest why did you change? Most folks I know who use a 22mm foresight do because 1)
That's what came on the rifle (e.g. Feinwerkbaus), 2) they have an extension tube already and want the larger tunnel to balance the sight picture. I know a few who chose to replace an 18mm tunnel with a 22mm on a standard barrel but they are in a minority.

Don't open the iris to try to increase the space around the foresight tunnel, that's not what it's for. Tweak the iris to control ambient brightness. If you want more space around the tunnel move the whole rearsight closer to you, this widens your field of view. But if that reduces your depth of focus unacceptably, and you already have a proper prescription lens, you may want to revert to the 18mm tunnel.

[btucker]

Out of interest why did you change? Most folks I know who use a 22mm foresight do because 1)
That's what came on the rifle (e.g. Feinwerkbaus), 2) they have an extension tube already and want the larger tunnel to balance the sight picture. I know a few who chose to replace an 18mm tunnel with a 22mm on a standard barrel but they are in a minority.

Don't open the iris to try to increase the space around the foresight tunnel, that's not what it's for. Tweak the iris to control ambient brightness. If you want more space around the tunnel move the whole rearsight closer to you, this widens your field of view. But if that reduces your depth of focus unacceptably, and you already have a proper prescription lens, you may want to revert to the 18mm tunnel.

I went with 22mm for my first move using metallic sights. Thought I would see more of the target and my hold then using 18mm. In looking at both, I'd say yes it does show more in the foresight tunnel...but it occupies more space within the rear sight tunnel. Agree the fix is increasing the distance between the two sights.

[Tim S]

That's interesting, I'd not considered that a larger tunnel could highlight movement in your hold. A larger foresight aperture can, if you were using one that didn't allow enough wobble room, and overlapped the target. But I hadn't thought that just a larger tunnel could.

Bear in mind if adding an extension tube it will make your hold appear to move more, assuming it doesn't actually do so by upsetting the balance.

[TenMetrePeter]

Maybe it's just me but I have always increased or reduced white space round the tunnel by moving the rear sight closer or further from the eye (eye relief). Altering the distance between sights is much less effective.
I do agree altering the diopter size doesn't do it either.

[Tim S]

Maybe it's just me but I have always increased or reduced white space round the tunnel by moving the rear sight closer or further from the eye (eye relief). Altering the distance between sights is much less effective.
I do agree altering the diopter size doesn't do it either.

Peter,

Remember that smalbore shooters don't have a maximum barrel/system length. Typically the barrel/action will be 30-33in (4-6in action + 25-27in barrel), on top of which we can add an extension tube. The maximum length of the tube is only practical, ie weight, balance, and wobble; in prone 12in isn't uncommon. If your eye relief is already comfortable, the you can slide the foresight along the tube to adjust the gap inside the rearsight.

[TenMetrePeter]

Thats true. I keep forgetting there's other rifles than air and with only half an inch foresight play, eye relief is my only option.

I cant see much difference in white space round the tunnel between 0.8 and 1.8 diopter diameter which remains an optical mystery to me.

[btucker]

That's interesting, I'd not considered that a larger tunnel could highlight movement in your hold. A larger foresight aperture can, if you were using one that didn't allow enough wobble room, and overlapped the target. But I hadn't thought that just a larger tunnel could.

Bear in mind if adding an extension tube it will make your hold appear to move more, assuming it doesn't actually do so by upsetting the balance.

I use a set of non adjusting aperture discs for the front. Never tried an adjustable iris up front.

[btucker]

Maybe it's just me but I have always increased or reduced white space round the tunnel by moving the rear sight closer or further from the eye (eye relief). Altering the distance between sights is much less effective.
I do agree altering the diopter size doesn't do it either.

I agree, you can get more white space just by moving up on the sight. But I'm already an inch away, already cut a gap in my visor just to not touch the rear sight:)

[Tim S]

I use a set of non adjusting aperture discs for the front. Never tried an adjustable iris up front.

Nothing wrong with inserts. Sometimes simple is best. An adjustable front iris is nice if you adjust a lot for light, but by no means essential. I use one only because I like a very thick ring, and a floating ring.

[Pheyden]

Just a simple extra suggestion. I have found that a little extra white space between the bull and the front sight orifice, will help greatly.

[Pheyden]

Just a simple extra suggestion. I have found that a little extra white space between the bull and the front sight orifice, will help greatly.

[JSBmatch]

I know a couple of people who have changed from M-22 to M-18 foresight tunnels on air rifle