Puzzle backsight

[Patrick Chadwick]

What, please, is this? Yes I know it's a backsight, but off what?

Attachment 21241

OK, this is not a Bren part, but the people who know what this is are maybe more likely to be found here than on the rifle forums.

As a true packrat, I picked this up some time ago for no better reason than that I was intrigued by the mechanism.

I am not sure, but I think it might be from a Browning machine gun, or something similar. The frame is marked on the left side with M2 & '06.AMM

Attachment 21239

M2 machine gun???
AMM = Ammunition??
but what does '06. signify?

The slider is the astonishing part of the construction.

Attachment 21240

As you move the slider up the scale, it shifts to the left.

Attachment 21238

A very complicated solution, as the more obvious answer would have been to mill a normal parallel-sided frame and skew the whole assembly (like the Buffington sight on a trapdoor). The skew angle, by the way, is much more than I have seen on any rifle, and the length of the scale indicates a trajectory that has much more curvature than, for example, a 30-06 rifle bullet.

The sight is missing a long threaded rod and an knurled knob in the slit at the top, to provide screw adjustment similar to the Enfield No. 4 sight. The rod must have been something like a 4-48 thread - if anyone has the exact thread dimension, I would like to know so that I can cut a new one.

The knurled knob on the right is to clamp the slider. It is spring-loaded so that you can unscrew it and push it in to detach the nut section from the threaded rod, for rapid adjustment. Without this feature, you would need a couple of minutes to go from 100 yards to 2600.

The scale, from 100 to 2600 yards, has 25-yd intermediate markings, with an adjustable pointer setting (left and right of the slider). Again, this seems to be a touch of engineering overkill, as you would need an artillery rangefinder to determine 2600 yards to a precision of 25 yards. (I guess this sight was made long before the days of laser rangefinders).

Finally, please note the large hole marked A-A FIRE. There are fine lines at the side so that you can set this to a precision of 25 yards as well - if the aircraft is so co-operative as to stand still in the air while you measure the range.

All in all, a very interesting device. Which is why I bought it, following the packrat's motto "You never know, it might come in handy one day".
What do you think lads - would it look good on a Long-Range Sharps?
(Sorry, don't all scream at once!)


Patrick

Information

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[gunner]

I would say it is from a Browning 1917 A1
Browning M1917A1 gun Picture & Browning M1917A1 gun Photo

Google-Ergebnis für http://www.tsmanufacturing.com/Lloyd%201917A1%20Build/Lloyd%201917A1%20Build%20008.jpg

Scroll down Patrick!

[Patrick Chadwick]

Brilliant Ulrich!

The photo in the link is so good that I can now make the leadscrew! It seems to be 40 tpi.
About 148 turns - you would be busy for a long time if there was no release button on the side!

[gunner]

You´re always welcome, Patrick!

[Lee Enfield]

I would say it is from a Browning 1917 A1
Browning M1917A1 gun Picture & Browning M1917A1 gun Photo

Close, but wrong, the AN-M2 Browning machine gun was used as an aircraft gun.

Our British cousins would refer to this as a "Colt-Browning"
Basically a narrower 1919 which cycles much faster than normal
Browning AN-M2 Aircraft M.G. (.30-06)
Browning Machine Guns

[Patrick Chadwick]

So whichever one it was - why the sight calibration in 25 yard intervals, with a screw thread adjustment that is even finer? For bench-rest machine-gunning, or what?

[tankhunter]

Patrick, You do not advise as to how long this sight is dimention wise. It LOOKS to be the version from a 1917 Watercooled Browning .30" Cal MG. The M2 & '06, I believe, refer to the models of Ammo IE: M2 Ball, & 1906 Sprringfield Patt Rifle ammunition. I was involved in the manufacture of Browning M2Hb .50" Cal MG's for many years. So have 'Played with fiftys & thirties a lot!
I CAN tell you that the thread start of the eleveating screw is a Multi-thread start version.
They DIFFER for a .30" cal to a .50" cal just to complacate things! And to make things worse, there is a three start, & a four start thread version as well!
I would try numrich Arms or someone like that in the US for an elevating screw. It is a VERY difficult thing to manufacture!

[browningautorifle]

Lee Enfield, the aircraft guns did not have ground sights. This sight is for the 1917 guns. M2 refers to ammo.

Patrick, the fine increments are just because that's how they did it in those days. They didn't understand it didn't matter and the beaten zone would cover that much distance. The next gun had only major markings.

[Patrick Chadwick]

Patrick, You do not advise as to how long this sight is dimention wise.

122 mm overall

The M2 & '06, I believe, refer to the models of Ammo IE: M2 Ball, & 1906 Sprringfield Patt Rifle ammunition.

That's what I guessed.

The M2 & '06, I believe, refer to the models of Ammo IE: M2 Ball, & 1906 Sprringfield Patt Rifle ammunition.

Sounds plausible. (What else could it be?)

I CAN tell you that the thread start of the eleveating screw is a Multi-thread start version.

Oh dear, oh dear!

It is a VERY difficult thing to manufacture!

You are so right!


Patrick

[Mk VII]

This appears to be a leaf made in 1933 for the M1 bullet that was modified for the 'new' M2 bullet in 1939 or after. As its characteristics suited any stocks of the M1906 bullet that remained, it was marked for that as well.