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Discussion Starter #1
I picked up a like new brass gunners quadrant at, of all places, a marine flea market in Hollywood FL.
It's marked in mills of elevation and not degrees.
Does anyone know why the army used mills?
I ought to know since I was in the artillery but I was in a Nike guided missile school as an instructor and never even saw a field piece fired. Shot down lots of drone aircraft though.
It may have something to do with the amount of range advance with increased elevation????:confused:
Its going to help when I fire my BP cannons. I will be able to get repeatable elevations no matter the ground level. My home made quadrant with a pendulum is not very accurate.
BTW As a matter of interest, mills means "milliradians" or 1/1000 of a radian and there are 2 Pi radians in a circle.
 

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we had those M1 gunners quadrants as Vulcan crewmembers......they were used for indirect fire, we were also issued with M2 compasses, boresight scope and our azimuth indicator was all in mills.

as to why the army uses mils instead of degress, it's not just the army that uses it, measurement in mils is mainly used in artillery, to correct the trajectory for indirect fire . This was done mainly because mils are a finer measurement than degrees and enabled them to be more accurate, when your lobbing shells at 10+ miles you need a more precise measurement so you don't fall short and clobber your own forces, for every 1,000 meters a mil off is like 1 meter......if I recall,

actually it's 6280 mils in a circle for everybody else, but the military wanted a more precise measurement, so they went with 6400 mils as a complete circle.


I rememeber I had at one time a gunner's quadarant that was dated from the 1940, when I did a end-to-end check, to factor in the error of the thing....it just about maxed out the fine adjustment .......we had some really antique ****.

I'd like to find one, just for remberance then anything else......set up next to my M168 cannon bolt and my shinny 20mm dummy round on my bookase.

did yours come with the case?
 

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Quadrant,gunners,M1...Must be calibrated..An operator cannot adjust the quadrant...Without the proper training you are farting in the wind...
 

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Discussion Starter #4
Slowfire-
You are correct. My quadrant uses 6400 mills total for a circle.
I checked it with a master machinist level on a surface plate with precision layout angle plates and it is dead on.
Just like the army to change the measurement from the scientfic one.
A radian is the angle where the radius equals the arc of the circle for whatever that's worth.
SARCO had M1 quadrants, according to SGN ads, a few months ago.
BTW I found out on Google that the Russians use 6000 mills per circle.
I want to find a TM for the quadrant if one exists.
I did not get a case with mine but that's OK since I intend to us it with my cannons.
 

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Slowfire-
You are correct. My quadrant uses 6400 mills total for a circle.
I checked it with a master machinist level on a surface plate with precision layout angle plates and it is dead on.
Just like the army to change the measurement from the scientfic one.
A radian is the angle where the radius equals the arc of the circle for whatever that's worth.
SARCO had M1 quadrants, according to SGN ads, a few months ago.
BTW I found out on Google that the Russians use 6000 mills per circle.
I want to find a TM for the quadrant if one exists.
I did not get a case with mine but that's OK since I intend to us it with my cannons.

The US military went with the 6400-mil circle for quite good reasons: it's more than accurate enough, and it's considerably easier to do the math in one's head when 90 degrees equals 1600 mils, as opposed to 1570.75 mils... Or when cardinal directions can be neatly broken down into 200 mil blocks...

The "scientific" version is great, when you're in a lab, well-rested and well-fed, with no one trying to kill you. At 0330, in the rain, after being up for 60+ hours on cold coffee and MREs, "good enough for what it's for" wins.
 

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For some interesting information go to "Browning Machine Guns" and scroll down to "Clinometer". The machine gun clinometer is similar to the gunners quadrant. This sight also has pictures of both.
 

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6400 for the US , my warpac OEM2 range finder is graduated in 6000 mil circles/ meters.. I had a old compass I got frm a elderly relative that was graduated in 6400... I didn't know why then . I hope I can find it now :( calibrating a gunner's quadrant can be found in the tm for the 1917 browning ... along w the Q E tables for for firing over friendly advancing troops:eek: there are 2 quadrants , they differ only in size....
 

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I picked up a like new brass gunners quadrant at, of all places, a marine flea market in Hollywood FL......
And it's a good thing you did because some weekend sailboater would have bought it thinking it was a sextant and ended up in Antartica instead of some carri-bean paradise!:D

Cool find, see neat stuff sometimes comes to you when you least expect it...
 
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