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GIFT OF
i
No. 1957
DESCRIPTION
OF
TELESCOPIC MUSKET SIGHTS
MODELS OF 1908 AND I9I3
(FOUR PLATES)
DECEMBER 14, 1908
REVISED JULY 22, 1912/r ^OFTHE^^
REVISED NOVEMBER X8, ct^^ y E R S 1 1^ y
v o . OF
WASHINGTON
GOVERNMENT PRINTING OFFICE
1917
No. 1957
DESCRIPTION
OF
TELESCOPIC MUSKET SIGHTS
MODELS OF 1908 AND I9I3
{FOUR PLATES)
DECEMBER 14, 1908
REVISED JULY 22, 1912
REVISED NOVEMBER 18, 1915
WASHINGTON
GOVERNMENT PRINTING OFFICE
1917 .
Wab Department, .
Office of the Chief of Ordnance,
Washington, November 18, 1915,
This manual is published for the information and government of the Regular
Army and Organized Militia of the United States.
By order of the Secretary of Wftr :
William Crozier,
Brigadier General, Chief of Ordnance.
104718—17 (3)
363177
Digitized by the Internet Archive
in 2007 with funding from
IVIicrosoft Corporation
http://www.archive.org/details/descriptionoftelOOunitrich
DESCRIPTION OF TELESCOPIC MUSKET SIGHTS.
MODEL OF 1908.
1. Throughout this description frequent reference is made b}^
number to the photographic Plate I and to the sectional drawing,
Plate II. On either plate a given number refers to the same part of
the instrument. A nomenclature table, arranged in sequence of the
reference numbers, will also be found on page 7.
2. The telescopic musket sight consists of three essential parts, the
telescope, indicated by numbers 1-11 and 20-28, Gl-62, Plate I. the
lever (50-60), on which the telescope is mounted by a vertical axis;
and the slide (30-39). to which the lever is secured b}^ a horizontal
axis, while graduated dials provide means for turning the instrumei<t
on both of these axes.
THE TF.LESCOPE.
3. In the telescope body (1) (see PL II) is mounted the objective
cell (10) for the objective (9), which has a clear aperture of ^f inch,
a focal length of 7 inches, and gives, with the eyepiece, a power of 6
diameters and a field of 4J°. The telescope is provided with Porro
erecting prisms (21) (21), mounted in accurately milled recesses in
the prism holder (20) and held in place under constant pressure by
the prism cap springs (23) of the prism caps (22) (24), the caps being
fastened by the prism cap screws (25). ^ The telescope has a reticule
holder (2) into which is spun the glass reticule (3), on which are
etched vertical and horizontal cross lines and stadia lines, the latter
being so placed. that they span the height (5 feet 8 inches) of an aver-
age man standing at a distance of 1,000, 1^500^ and 2ft00 yards ^ re-
spectively. The telescope has an eye-lens holder (5) for the Steinheil
triple achromatic eye lens (4). The holder has a long threaded por-
tion by which it is screwed into the body and by which means for
focusing is secured. The eye-lens holder is locked in position by the
focusing lock nut (8) and is provided with an eye cap of soft rubber
( 6 ) , fastened by the eye-cap ferrule ( 7 ) . On each telescope is fastened,
hy means of table screws (28), the wind and range table (26) and
drift table ^27) and on the rear face is fastened a range table {61)
which shows the ranges corresponding to the three stadia lines.
(5)
.^i^$He"^le>fer- (56^)' slipports the telescope body by means of the
adjusting screw (58). This screw forms a vertical axis for the
telescope, and the segmental worm gear (A), together with the drift
screw (53) and its graduated drift dial (55) , provide means for turn-
ing the telescope on this axis for drift and wind corrections.
5. The slide (30) supports the lever (50) on the horizontal axis (C).
The pin (D) of the lever engages with the internal hardened steel cam
(E) of the range dial (32), and is kept in contact with it by the lever
spring (31). The inner circumference of the range dial is conical
and fits in a conical bearing, so that it can be clamped in any desired
position by tightening the range-dial knob (34) against the keyed
range-dial washer (33). By turning the dial (32) the telescope is
rotated on the horizontal axis (C) , giving the proper depression angle
for range correction.
The telescopic sight hrachet is assemhled to the receiver of the rifle hy
means of screws. The sight is mounted on the hracket hy means of the
dovetail (B) in the slide {30) and is held in position hy means of the
catch {S6\ which may engage in either of the two notches in the hracket.
The catch can be released by pressing the catch nut (38).
ADJUSTMENT OF THE INSTRUMENT.
For focus. — In adjusting the instrument at the factory the reti-
cule is set exactly in the focal plane of the objective, which has a
universal focus beyond 100 feet, and the eyepiece is set for the vision
of an average observer. Should alteration of the focus of the eye-
piece be necessary to suit special conditions, unscrew the focusing
lock nut (8) and screw the eyepiece out or in until the cross lines of
the reticule are sharply defined, and until at the same time the image
of the target is clearly visible. Then move the head up and down,
so that the eye may travel across the eyepiece. If the focus has been
correctly found there will be no parallax, that is, no apparent motion
of the cross wires with reference to the target when the eye moves
across the field. The focus being accurately adjusted, be sure to
lock the eye-lens holder by tightening the focusing, lock nut (8).
The rubber eye cap can now be turned, without affecting the focus,
to any desired position. If the rubber cap does not turn easily,
loosen the eye-cap ferrule (f ) and tighten it again when the adjust-
ment is made.
For elevation. — The range dial is graduated from 0 to 3,000 yards
by 20-yard divisions. To make elevation adjustment attach the
telescopic sight to the bracket of the rifle, being sure that both the
slide and the bracket are perfectly clean, secure the rifle in a fixed
rest, and set the service sight of the rifle at 500 yards. Set the range
dial of the telesoopic sight at the same range and clamp it. The cross
wires of the telescopic sight and the line of sight of the i^fie through the
service sight should then bisect the target exactly. If the cross wires
of the telescopic sight are too high, unscrew the hexagon adjusting-
screw nut (59 ) , using the screw driver provided with the sights and turn
the adjusting screw (58) clockwise, which will cause the cross wires
to drop on the target. Turning the adjusting screw in the opposite
direction will make the cross wires rise. After the adjustment is
made be sure to tighten the nut. The rifle is then fired several shots
to test elevation^ the necessary correction being made by the Tnoverrient
of the adjusting screw until a satisfactory elevation is obtained.
For drift. — The graduations on the drift dial (55) correspond to
1 inch on the target at a range of 100 yards. Turning the dial clock-
wise corrects to the right, as indicated'by the letter (R) and counter-
clockwise to the left, as indicated by the letter (L). There are 38
points of left and 46 points of right drift correction. The drift dial
should read " 0 " when the optical axis of the instrument is parallel
with the bore of the rifle. Should it be necessary to adjust the dial;
secure the rifle in a fixed rest, make the optical axis of the instrument
parallel with the line of sight through the service sight, by sighting at
some distant object, loosen the two drift-dial screws (57) which will
permit rotating the dial without moving the drift screw, set the dial
exactly at " 0 " and clamp the screws firmly against.
Nomenclature table.
1. Body.
32.
Range dial.
2. Reticule holder.
33.
Range-dial washer.
3. Reticule.
34.
Range-dial knob.
4. Triple eye lens.
35.
Spring cotter (for knob ) .
5. Triple eye-lens holder.
36.
Catch.
6. Eye cap.
37.
Catch spring.
7. Eye-cap ferrule.
38.
Catch nut.
8. Focusing lock nut.
39.
Range-dial washer pin.
9. Objective.
50.
Lever.
10. Objective cell.
51.
Spanner nuts.
11. Body screws.
- 52.
Spring cotters (for nuts)
20. Prism holder.
53.
Drift screw.
21. Prisms.
54.
Drift-screw washer.
22. Prism cap.
55.
Drift dial.
23. Prism-cap springs.
56.
Drift-dial washer.
24. Prism cap.
57.
Drift-dial screws.
25. Prism-cap screws.
58.
Adjusting screw.
26. Wind and range table.
59.
Adjusting-screw nut.
27. Drift table.
60.
Drift-dial pin.
28. Table screws.
61.
Range table.
30. Slide.
62.
Range-table screws.
31. Lever spring.
70.
Screw driver.
POUCH.
Model of 1911 for telescopic musket sights.
The pouch furnished for the telescopic sight is made of russet collar
leather. It is provid^ed with a douhle hook and a leather straj)^ so that
it can he carried either on the cartridge helt or over the shoulder.
MODEL OF 1913.
The telescopic musket sight, model of 1913, is shown on photo-
graphic Plate III. A sectional drawing of the instrument is shown
on Plate IV. A nomenclature table, with illustration number, piece
mark, and drawing number, will be found below. The illustration
numbers given in nomenclature table refer to Plates III and IV.
This instrument is almost identical with the telescopic musket
sight, model of 1908, and differs only the following particulars :
{a) The objective (27) is held in the objective cell (24) by the
objective retaining ring (25) which is held in- place by the objective
retaining nut (26).
(b) The reticule holder (41) is held in the telescope body (5) by
the reticule-holder nut (42), which screws into the telescope body.
The reticule is prevented from turning by the reticule-holder lock
screw (43).
{c) The triple eye-lens holder (50) has a short threaded portion
by which it is screwed into the telescope body (5) and by means of
which the instrument is focused. To alter the focus, remove the
focusing-lock collar cap (21), loosen the focusing-lock collar (19) by
unscrewing the focusing-lock collar screw (20), then screw the triple
eye-lens holder (50) in or out until the cross lines on the reticule (40)
are sharply defined and the image of the target is clearly visible.
After the focus has been determined, lock the triple eye-lens holder
(50) by screwing the focusing-lock collar screw (20) into the telescope
body until the focusing-lock collar bears tightly enough to prevent
turning, then replace the focusing-lock collar cap (21). The rubber
eye cap (18) can now be turned without affecting the focus of the
instrument. If the eye cap (18) does not turn easily, loosen the eye-
cap ferrule (17) and tighten again when adjustment is made.
Nomenclature.
Illustra-
Illustra-
tion No.
tion No.
1.
Adjusting-screw spanner nut.
28. Prism holder.
2.
Adjusting-screw nut.
29. Prism-holder screw.
3.
Adjusting screw.
30. Prism cap.
4.
Adjusting-screw hole cap screw.
31. Prism-cap spring.
5.
Body.
32. Prism-cap screw.
6.
Catch nut.
33. Prism.
7.
Catch spring.
34. Range-dial knob.
8.
Catch.
35. Range-dial washer.
9.
Drift table.
36. Range-dial washer pin.
10.
Drift-table screws.
37. Range table.
11.
Drift-dial washer.
38. Range-table screws.
12.
Drift-dial washer screw.
39. Range dial.
13.
Drift screw.
40. Reticule.
14.
Drift-screw washer.
41. Reticule holder.
15.
Drift dial.
42. Reticule-holder nut.
16.
Drift-dial pin.
43. Reticule-holder lock screw.
17.
Eye-cap ferrule.
44. Standard split pin.
18.
Eye cap.
45. Slide.
19.
Focusing-lock collar.
46. Screw driver wrench.
20.
Focusing-lock collar screw.
47. Spanner nut.
21.
Focusing-lock collar cap.
48. Standard split pin.
22.
Lever.
49. Triple eye-lens holder ferrule.
23.
Lever spring.
50. Triple eye-lens holder.
24.
Objective cell.
51. Triple eye lens.
25.
Objective-retaining ring.
52. Wind and range table.
26.
Objective-retaining nut.
53. Wind and range table screws.
27.
Objective.
CARE AND PRESERTATION.
Telescopic sights are necessarily delicate instruments and must
not be subjected to rough usage, jars, or strains. When not in use
the telescope should be kept in its pouch and stored in a dry place.
It should be occasionally examined to insure its, not being corroded,
and all traces of dust or moisture should be removed before being put
away. To obtain satisfactory vision the glasses should be kept
perfectly clean and dry. In case moisture collects on the glasses,
place the telescope in a gentle warmth ; this is usually sufficient to
remove it. A piece of chamois skin or a clean linen handkerchief
will answer for cleaning purposes, care being taken that the cleaning
material does not contain any dirt or grit. These sights before issue
are carefully adjusted to selected rifles and their adjustment proven
by actual firings. The prism holder should never be opened except
by a competent person. The body of this telescope and its objective
must remain intact. The eyepiece can be /removed after loosening
the focusing lock nut and the eyelens and reticule then cleaned.
Before incasing the prisms at the factory the interior of the body is
10
thoroughly cleaned and all particles removed. If any fine particles
should be left in the body or if the body should he opened and particles
enter, they wUl settle upon the reticule and when magnified by the
eye-lens obscure the vision. Small holes are punched through the
rubber eye cap to permit the escape of air on recoil, thereby prevent-
ing suction on counter recoil.
Wab Depaetment,
Office of the Chief of Oednance,
Washington, November 18, 1915.
December 14, 1908.
Revised July 22, 1912.
Revised November 18, 1915.
FoEM No. 1957.
Ed. June 13-17—3,000.
39275-702.
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