Central No.4 Clicks

[BobGee]

I am a newcomer to the forum. I signed up a while ago but have just become a contributing member. I have a No.4 Mk.2 and have just acquired a Central sight with a universal mounting plate with a Leverlock screw and a simple one hole iris. I have an adapter on its way so I can fit my Gehmann adjustable iris.

To cut to the chase, I suspect that my Central sight questions might have been answered already but there is so much information on the website that even using the search function returns more posts and threads than one can easily deal with. It also seems to be very easy to lose a thread/post and not find it again!

On one post I found the following:

“The very basic way to find out what a "click" is worth on any sight is simply to count the clicks for 5 MoA which is the distance between two of the engraved lines on the sight face, 10 clicks = 1/2 MoA 20 clicks = 1/4 MoA.”

My question is: is it not possible to determine which type of sight you have by the total number of clicks per revolution of each knob? I'd have thought that, as a manufacturer, it would have been easier to increase/decrease the number of detent cuts/divots in the underside of the knobs than to provide different threading on the adjusters with all that that entails.

Incidentally, are the 1/3 MoA adjusters just used with the 7.62 sights?

I'm also curious as to how the adjusters are held in position as I have not found signs of cross pins through the frames beneath the knobs to prevent the adjusters moving away from the posts when “unscrewing”.

Any info on these three points would be of great interest, thank you.

Bob

[Alan de Enfield]

Don't forget that the MOA of each click will also depend on to which rifle the sight is fitted, and varies by the sight radius.

A forum member 'parashooter' did a very good study and comparison of the differences between the No5 800yd sight when it was used on a No5 and when it was used on a No4.

A brief extract ..........

The 800-yard sight has a click value of ~0.66 MOA, with the No.5's 23" sight radius, but, when mounted onto a No4 with the 28" sight radius, it would yield ~0.55 MOA.

A 20% difference !

[tiriaq]

I don't know about clicks per revolution, but studying the Vernier scale as the knob is turned will tell you how many clicks there are to the minute. As mentioned, the actual change of POI on the target will be affected by the sight radius.
It will be different with your No. 4 compared with a 30" barreled target rifle.
Clicks per minute is not related to caliber.

[muffett.2008]

The 3rd minute sight is specifically for Metric targets, as opposed to the standard 1/2 minute sight primarily used with Yardage.
The 1/4 minute sight was originally used with smallbore, but as rifle accuracy improved, a combination of half and quarter became popular.
The thread spindles are the same, clicks determined by detents in the knob.

Calibre and Elevation are determined by the Range Scale.

[Rick]

Somewhat adrift from the OP's question, I once had the very bad idea of measuring the movement per click (and between scribed range lines) on issue No. 4 sights.

The brief version is that I started out knowing that these were sights made for military use, most of them manufactured during war where the objective was the rifleman being able to hold Minute Of Bad Guy during a TIC. And of course the reality of backlash in the mechanism, etc. But I didn't realize that the differences through the range of the screw's movement up and down would be so great.

Anyways, watching the measured movement change as I screwed the sight up and down through the range... I finally realized I was about to go down a rabbit hole with no satisfactory ending if I pursued that in search of some consistency or insight.

My Long Branch is normally wearing a Parker Hale vernier rear sight for belly shooting these days anyways, strictly for fun... but that was maddening back then, sorting through the coffee tin of rear sights I had accumulated, looking for a magical one.