No4 Mk1 micromerer rear sight MOA adjustments?

[ANDYZ28]

I have a No4 Mk1 1942 Long Branch that I have installed an issue type rear sight on to. What is the value of the clicks on this sight.

Thanks, Andy

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[Patrick Chadwick]

Just measured on my No.4:

100 clicks = 19.58mm = 0.771"
Sight radius = 720mm = 28.35"

Tan (100 clicks) = 0.0272
100 clicks = 0.56°= 0.336'
Allowing for counting mistakes, I would say "about 1/3 of a minute

An odd value, I'll check that later

[Beerhunter]

What is the value of the clicks on this sight.

It is based on the ballistics of the Mk.VII ammunition rather than MOA.

[jmoore]

The Mk.I sight assembly does have click values, the hash marks on the sight frame are .303"SAA based.

Rather than trig, Patrick Chadwick, I just use proportional values.0.00771"/28.35"=x/(100ydx36"/yd) So, x= (0.00771x3600)/28.35= ~0.979" change per click at 100yds.

OR, PDClose to 1 MOA per click.

---------- Post added at 04:23 AM ---------- Previous post was at 04:17 AM ----------

It's not a pretty post, but i'm tired of trying to edit it in "Mobile"!

[Patrick Chadwick]

Thanks Jmoore! I knew something was wrong, but was too tired to check it.
OK, 2 cups of coffee later, I see that I wote 0.56° where it should have been
1.56° =116"

So 1 click = 1.16 minute.

BTW, as far as I can measure this thing, the screw thread looks likes 44 tpi, but is cut double-start. I.e. effectively 22 tpi. Could someone else please check that while I look for my glasses!

Patrick

[jmoore]

Given the slop in the sights and all, plus minor errors in ranging (when do you ever KNOW the front sight is EXACTLY 3600" from a 100yd target, etc.) I reckon calling it 1 MOA clicks is close enough.

If you really want to be picky, a 1 MOA change at 100yds is more like 1.04".

[Patrick Chadwick]

I reckon calling it 1 MOA clicks is close enough.

I agree, and don't want to be picky. I mentioned the thread because I wondered if they simply chose 22 tpi as being a standard BSF pitch, for which threading gear would have been available. The next pitch, 26 tpi, would have been much finer than 1 MOA, i.e. unnecessarily fine. And 24 tpi, which would be very close indeed to 1 MOA and seem obvious to someone in the USA, was not a usual pitch for British threads

OK, before someone chips in and says that is useless speculation, well yes, you may be right, but it is still interesting to think through "How would I have done it if I had been there?". Theoretical considerations are often overridden by simple practical considerations like "what tools have we actually got, what parts are in the bin?"

Patrick

[jmoore]

Originally Posted by Patrick Chadwick: "Theoretical considerations are often overridden by simple practical considerations like 'what tools have we actually got, what parts are in the bin?'"

Except it seems with any sort of gun part, military or commercial. ESPECIALLY regarding oddball threads- it's almost a requirement. Mauser 98 action screws come to mind as a "metric" example.

---------- Post added at 05:58 AM ---------- Previous post was at 05:55 AM ----------

1/4"/28 tpi or 20tpi, I think for the Mauser.

[ANDYZ28]

I was prompted my question is that we will be firing a No4 Mk1 FAZ at the upcoming CMP Eastern Games, and with no chance to "zero" the rifle prior to the match, the click values are important. We only have 5 shots for sighting prior to "record fire". I have applied a mechanical zero to the windage using the borescope, DAP method, and I think we will be OK for windage. Fal all practical purposes, each click will represent 2" @ 200 yards?

We will be using handloads at less than military ball ammo spec. w/174 grain Sierra Matchking bullets @ 200 yards.

Thanks, Andy

[jmoore]

Fal(sic) all practical purposes, each click will represent 2" @ 200 yards? We will be using handloads at less than military ball ammo spec. w/174 grain Sierra Matchking bullets @ 200 yards.

Yah, 1 click=1 MOA so 2" at 200yds is pretty close.

Lower velocity rounds will make for more drop than expected at longer ranges, but may actually hit higher than expected if you did previously zero w/ Mk.VII spec. ammo at the same distance. (Closer distances only- the effect diminishes as distance increases, which isn't going to affect you.) You DO have some sort of actual zero by shooting, I hope!


P. C.- Six clicks per revolution= 16 2/3 revs. per 100 clicks, so it works out to be 21.6 tpi. Probably 22 tpi? A simple thread pitch gage won't discern the difference. Optical comparitor anyone?