yC-MRLF *B 7M itl 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 instrumeifer- (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 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 " " 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 " " 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. O -^ H^^ ■