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Boresights and Boresight Telescopes, O.P. 1449, 1949, describes the instruments used to align the gun sights with the guns they aim.

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RESTRICTED
OP 1449
Boresights and Boresight Telescopes
6 December 1949


BORESIGHTS AND BORESIGHT TELESCOPES
O.P. 1449

TABLE OF CONTENTS
 

Chapter 1 Page
INTRODUCTION 1
  Types of Boresights 1
  Breech Bar Boresights 1
  Boresights With Self-Contained Optics 2
  Boresighting 4
    Boresighting Procedure 6
  Sight Alignment 7
  References 8
Part 1
BREECH BAR BORESIGHTS 15
Chapter 2
BORESIGHT TELESCOPES 16
  Introduction 16
  Design Factors 16
  Notes on Care and Handling 16
Section 1
TELESCOPE MK 8 MOD 6 (BORESIGHT) 18
  Optical Characteristics 18
  Description 18
    Objective Lens and Draw Tube 19
    Crossline Lens and Mount 19
    Erecting System and Draw Tube 19
    Collective and Eyelenses and Eyepiece Adapter 20
  Disassembly, Telescope Mk 8 Mod 6 20
    Routine Before Disassembly 20
  Reassembly, Telescope Mk 8 Mod 6 27
    Routine Before Assembly 27
  Collimation 31
Section 2
TELESCOPE MK 75 MODS 0 and 1 (BORESIGHT) 32
  Optical Characteristics 32
  Description 33
    Objective Lens and Body Tube 34
    Telescope Draw Tube 34
    Crossline and Erecting Lenses 34
    Eyelenses and Eyepiece Mount 35
    Telescope Mk 75 Mod 0 35
  Disassembly, Telescope Mk 75 Mods 0 and 1 35
    Routine Before Disassembly 35
  Reassembly, Telescope Mk 75 Mods 0 and 1 41
    Routine Before Assembly 41
  Final Assembly and Collimation, Mods 0 and 1 43
 
Chapter 3 Page
BREECH BAR BORESIGHT EQUIPMENT 45
  Introduction 45
  Notes on Care and Handling 45
  Installation 46
    4-inch Boresight Mk 20 Mod 1 47
    5-inch Boresight Mk 29 Mod 0 47
    6-inch Boresight Mk 36 Mod 0 48
  Alignment 49
Part 2
BORESIGHT WITH SELF-CONTAINED OPTICS 55
  Design Factors 55
  Notes on Care and Handling 57
Chapter 4
20-MM BORESIGHTS 58
  Notes on Boresighting 20-mm Mounts 58
Section 1
20-MM BORESIGHT TOOL 59
  Optical Characteristics 59
  Installation 60
  Description 60
    Mandrel 60
    Weaver Telescope #298 60
    Weaver Telescope #330 62
  Disassembly, 20-mm Boresight Tool 63
    Routine Before Disassembly 63
  Reassembly, 20-mm Boresight Tool 67
    Routine Before Assembly 67
  Collimation, #298 68
  Collimation, #330 69
Section 2
20-MM BORESIGHT MK 1 MOD 0 70
  Optical Characteristics 70
  Installation 71
    Rear Sight Assembly 71
    Front Sight Assembly 71
    Removal 71
  Description 73
    Front Sight Assembly 73
    Rear Sight Assembly 74
  Disassembly, 20-mm Boresight Mk 1 Mod 0 74
    Routine Before Disassembly 74
  Reassembly, 20-mm Boresight Mk 1 Mod 0 77
    Routine Before Assembly 77
  Collimation 78


2
 
Section 3 Page
20-MM BORESIGHT MK 3 MOD 0 78
  Optical Characteristics 79
  Installation 79
    Rear Sight Assembly 79
    Front Sight Assembly 79
    Removal 80
  Description 80
  Disassembly, 20-mm Boresight Mk 3 Mod 0 81
    Routine Before Disassembly 82
  Reassembly, 20-mm Boresight Mk 3 Mod 0 83
    Routine Before Assembly 83
  Collimation 83
Chapter 5
40-MM BORESIGHTS 84
Section 1
40-MM BORESIGHT MK 1 MOD 0 84
  Optical Characteristics 84
  Installation 86
    Breech Assembly 86
    Muzzle Assembly 86
    Removal 86
  Description 87
    Muzzle Assembly 87
    Breech Assembly 87
  Disassembly, 40-mm Boresight Mk 1 Mod 0 89
    Routine Before Disassembly 89
  Reassembly, 40-mm Boresight Mk 1 Mod 0 90
    Routine Before Assembly 90
  Collimation 91
Section 2
40-MM BORESIGHT MK 2 MOD 0 92
Chapter 6
3-INCH BORESIGHT MK 30 MOD 1 93
  Optical Characteristics 94
  Installation 94
    Breech Assembly 94
    Muzzle Assembly 95
    Removal 96
  Description 96
    Muzzle Assembly 96
    Breech Assembly 97
  Disassembly, 3-inch Boresight Mk, 30 Mod 1 98
    Routine Before Disassembly 98
 
3-INCH BORESIGHT-Continued Page
  Reassembly, 3-inch Boresight Mk 30 Mod 1 104
    Routine Before Assembly 104
  Collimation 106
Chapter 7
4.2-INCH MORTAR BORESIGHTS 107
  Notes On Boresighting 4.2-inch Mortars 107
Section 1
4.2-INCH BORESIGHT (MORTAR) MK 1 MOD 0 107
  Optical Characteristics 107
  Installation 107
    Removal 108
  Description 108
  Disassembly, 4.2-inch Boresight (Mortar) Mk 1 Mod 0 109
    Routine Before Disassembly 109
  Reassembly, 4.2-inch Boresight (Mortar) Mk 1 Mod 0 109
    Routine Before Assembly 109
Section 2
4.2-INCH BORESIGHT (MORTAR) MK 2 MOD 0 111
  Optical Characteristics 111
  Installation 112
    Removal 112
  Description 112
    Telescope Adaptor 112
    Telescope Body Assembly 112
    Eyepiece Assembly 114
  Disassembly, 4.2-inch Boresight (Mortar) Mk 2 Mod 0 114
    Routine Before Disassembly 114
  Reassembly, 4.2-inch Boresight (Mortar) Mk 2 Mod 0 118
    Routine Before Assembly 118
  Collimation 120
Chapter 8
5-INCH BORESIGHT MK 35 MOD 0 121
  Optical Characteristics 121
  Installation 122
    Breech Assembly 122
    Muzzle Assembly 122
    Removal 123
  Description 123
    Muzzle Assembly 123
    Breech Assembly 123
  Disassembly, 5-inch Boresight Mk 35 Mod 0 125
    Routine Before Disassembly 125


3
 
5-INCH BORESIGHT-Continued Page
  Reassembly, 5-inch Boresight Mk 35 Mod 0 128
    Routine Before Assembly 128
Collimation 129
Chapter 9
5-INCH BORESIGHT MK 38 MOD 1 130
  Optical Characteristics 130
  Installation 130
    Breech Assembly 131
    Muzzle Assembly 131
    Removal 132
  Description 132
    Muzzle Assembly 132
    Breech Assembly 132
  Disassembly, 5-inch Boresight Mk 38 Mod 1 134
    Routine Before Disassembly 134
  Reassembly, 5-inch Boresight Mk 38 Mod 1 137
    Routine Before Assembly 137
  Collimation 138
Chapter 10
6-INCH BORESIGHT MK 37 MOD 0 139
  Optical Characteristics 140
  Installation 141
    Muzzle Assembly 141
    Breech Assembly 141
    Removal 142
  Description 142
    Muzzle Assembly 142
    Breech Assembly Housing 143
    Eyelens Mount 143
  Disassembly, 6-inch Boresight Mk 37 Mod 0 144
    Routine Before Disassembly 144
  Reassembly, 6-inch Boresight Mk 37 Mod 0 150
    Routine Before Assembly 150
  Collimation 152
Chapter 11
8-INCH BORESIGHT MK 31 MOD 0 153
  Optical Characteristics 153
  Installation 154
    Muzzle Assembly 154
    Breech Assembly 154
    Removal 155
  Description 155
    Muzzle Assembly 155
    Body Assembly 156
    Eyelens Mount 156
 
8-INCH BORESIGHT-Continued Page
  Disassembly, 8-inch Boresight Mk 31 Mod 0 157
    Routine Before Disassembly 157
  Reassembly, 8-inch Boresight Mk 31 Mod 0 164
    Routine Before Assembly 164
  Collimation 166
Chapter 12
NOTES ON MAINTENANCE AND OVERHAUL 167
  Shipboard Maintenance 167
    Transportation 167
    Stowage 167
    Handling 167
  Shop Handling 168
    Disassembly 168
    Cleaning Lenses 169
    Reassembly 169
    Lubrication 169
NUMERICAL LISTING OF PARTS 170
  Telescope Mk 8 Mod 6 (Boresight) 170
  Telescope Mk 75 Mod 0 (Boresight) 172
  Telescope Mk 75 Mod 1 (Boresight) 173
  20-mm Boresight Mk 1 Mod 0 174
  20-mm Boresight Mk 3 Mod 0 174
  40-mm Boresight Mk 1 Mod. 0 175
  3-inch Boresight Mk 30 Mod 1 176
  4.2-inch Boresight (Mortar) Mk 1 Mod 0 177
  4.2-inch Boresight (Mortar) Mk 2 Mod 0 177
  5-inch Boresight Mk 35 Mod 0 178
  5-inch Boresight Mk 38 Mod 1 179
  6-inch Boresight Mk 37 Mod 0 180
  8-inch Boresight Mk 31 Mod 0 182
PRECAUTIONS IN HANDLING BORE-SIGHTS AND BORESIGHT TELESCOPES 184
Table
1. Table of Boresights and Mounts With Which They Are Used 9
2. Table of Gun Mounts and Boresights Used With Them 11
3. Optical Characteristics, Boresight Telescopes 13
4. Table of Weights and Sizes of Bore-sights When Stowed in Carrying-Cases 14
5. Optical Characteristics, Boresights With Self-Contained Optics 14
6. Breech Bar Boresights 45


4
 
LIST OF ILLUSTRATIONS
 
Figure Page
1. Boresighting 3-inch Mount Mk 27 with 3-inch Boresight Mk 30 Mod 1 viii
2. Telescope Mk 8 Mod 6 (Boresight) 1
3. Typical Boresight Breech Bar 2
4. Typical Boresight Muzzle Disc 2
5. Typical Breech Bar Boresight Installation 2
6. Typical Breech Assembly 3
7. Typical Muzzle Assembly 4
8. Effect of Range on Boresighting 4
9. Mandrel Type Installation 4
10. Typical Self-Contained Optics Installation 5
11. Effect of Sight Misalignment 5
12. Antiaircraft Machine Guns are Bore-sighted at Expected Mean Firing Ranges 6
13. 16-inch Boresight Mk 2 Mod 0 in Carrying Case 15
14. Telescope Mk 75 Mod 1 (Boresight) in Carrying Case 15
15. Telescope Mk 8 Mod 6 (Boresight) 17
16. Optical Diagram-Telescope Mk 8 Mod 6 18
17. Telescope Mk 8 Mod 6-Cutaway 19
18. Telescope Assembly-Telescope Mk 8 Mod 6 21
19. Eyepiece Assembly 22
20. Eyepiece Collective Tube Assembly 23
21. Erecting System Draw Tube Assembly 24
22. Body Assembly 25
23. Crossline Housing Assembly 26
24. Objective Draw Tube Assembly 26
25. Adjusting Screw Housing Assembly 27
26. Assembly of Body Tube, Telescope Adaptor and Adjusting Screw Housing 29
27. FinalAssembly-Telescop e Mk 8 Mod 6 30
28. Telescope Mk 75 Mods 0 and 1 (Bore-sight) 32
29. Optical Diagram-Telescope Mk 75 Mods 0 and 1 33
30. Telescope Mk 75 Mod 1-Cutaway 33
31. Telescope Mk 75 Mod 0-Partial Cutaway 34
32. Telescope Assembly-Telescope Mk 75 Mods 0 and 1 36
33. Eyepiece Assembly, Mods 0 and 1 38
34. Eye lens Mount Assembly, Mods 0 and 1 38
35. Crossline and Erecting System Draw Tube Assembly, Mod 0 39
 
Figure Page
36. Crossline and Erecting System Draw Tube Assembly, Mod 1 40
37. Erecting Lens Mount Assemblies Mods 0 and 1 41
38. Crossline Lens Mount Assembly, Mod 0 41
39. Breech Bar of 8-inch Boresight Mk 26 Mod 0, Installed 46
40. Installation of Typical Muzzle Disc. 46
41. 5-inch Boresight Mk 29 Mod 0-Breech Adaptor Installed 47
42. 6-inch Boresight Mk 36 Installed for Initial Alignment 48
43. 6-inch Boresight Mk 36-Final Installation for Boresighting 48
44. Adjustment of Crosslines to Muzzle Disc 50
45. 6-inch Boresight Mk 36 Mod 0 51
46. 3-inch Boresight Mk 18 Mod 0 52
47. 5-inch Boresight Mk 29 Mod 0 52
48. 4-inch Boresight Mk 20 Mod 1 53
49. 5-inch Boresight Mk 25 Mod 53
50. 8-inch Boresights Mk 26 Mod 0 and Mk 30 Mod 0 54
51. 12-inch Boresight Mk 34 Mod 0, 14-inch Boresight Mk 2 Mod 0, and 16-inch Boresight Mk 2 Mod 0 54
52. 5-inch Boresight Mk 35 Mod 0 in Carrying Case 56
53. Aligning Gun Sight Mk 14 Mounting Bracket 58
54. 20-mm Boresight Tool 59
55. 20-mm Boresight Tool Installed 60
56. Optical Diagram-Weaver Telescope #298 61
57. Optical Diagram-Weaver Telescope #330 61
58. Cutaway-Weaver Telescope #298 61
59. Cutaway-Weaver Telescope #330 62
60. 20-mm Boresight Tool Assembly 63
61. Telescope Assembly-Weaver #298 64
62. Eyepiece and Crosswire Tube Assemblies-Weaver #298 65
63. Eyepiece and Corsswire Tube Assemblies-Weaver #330 66
64. Telescope Assembly-Weaver #330 67
65. 20-mm Boresight Mk 1 Mod 0 70
66. Optical Diagram-20-mm Boresight Mk 1 Mod 0 71
67. 20-mm Boresight Mk1 Mod 0-Installed 72
68. Cutaway-20-mm Boresight Mk 1 Mod 0 73


5
 
Figure Page
69. Rear Sight Assembly 75
70. Telescoping Tube Assembly 76
71. Front Sight Assembly 77
72. 20-mm Boresight Mk 3 Mod 0 79
73. Optical Diagram-20-mm Boresight Mk 3 Mod 0 79
74. 20-mm Boresight Mk 3 Mod 0-Installed 80
75. Cutaway-20-mm Boresight Mk 3 Mod 0 81
76. Rear Sight Assembly 81
77. Front Sight Assembly 82
78. 40-mm Boresight Mk 1 Mod 0 85
79. Optical Diagram-40-mm Boresight Mk 1 Mod 0 85
80. 40-mm Boresight Mk 1 Mod 0-Installed 86
81. Cutaway-40-mm Boresight Mk 1 Mod 0 87
82. Breech Assembly 88
83. Eyelens Mount Assembly 89
84. Muzzle Assembly 90
85. Cutaway-40-mm Boresight Mk 2 Mod 0 92
86. 40-mm Boresight Mk 2 Mod 0 Installed 92
87. 3-inch Boresight Mk 30 Mod 1 93
88. Optical Diagram-3-inch Boresight Mk 30 Mod 1 94
89. 3-inch Boresight Mk 30 Mod 1-Breech Assembly Installed 95
90. 3-inch Boresight Mk 30 Mod 1-Muzzle Assembly Installed 96
91. Cutaway-Muzzle Assembly, 3-inch Boresight Mk 30 Mod 1 96
92. Cutaway-Breech Assembly, 3-inch Boresight Mk 30 Mod 1 97
93. Eyepiece Housing Assembly 99
94. Filter and Eyepiece Mount Assemblies 101
95. Body Assembly 101
96. Erecting Lens Mount Adaptor Assembly 102
97. Muzzle Assembly 103
98. Support Arm Assembly 103
99. 4.2-inchBoresight (Mortar) Mk1 Mod 0 107
100. 4.2-inch Boresight Mk 1-Installed 108
101. Cutaway-4.2-inch Boresight Mk 1 108
102. Boresight Assembly 110
103. 4.2-inch Boresight (Mortar) Mk2 Mod 0 110
104. Optical Diagram-4.2-inch Boresight Mk 2 111
105. 4.2-inch Boresight Mk 2-Installed 112
 
Figure Page
106. Cutaway-4.2-inch Boresight Mk 2 113
107. Telescope Assembly 115
108. Sleeve Assembly 116
109. Eyepiece Assembly 116
110. Telescope Adaptor Assembly 118
111. 5-inch Boresight Mk 35 Mod 0 121
112. Optical Diagram-5-inch Boresight Mk 35 Mod 0 122
113. 5-inch Boresight Mk 36 Mod 0-Installed 123
114. Cutaway-5-inch Boresight Mk 35 Mod 0 124
115. Breech Assembly 125
116. Muzzle Assembly 127
117. 5-inch Boresight Mk 38 Mod 1 130
118. Optical Diagram-5-inch Boresight Mk 38 Mod 1 131
119. 5-inch Boresight Mk 38 Mod 1-Installed 132
120. Cutaway-5-inch Boresight Mk 38 Mod 1 133
121. Breech Assembly 134
122. Muzzle Assembly 136
123. 6-inch Boresight Mk 37 Mod 0 139
124. Optical Diagram-6-inch Boresight Mk 37 Mod 0 140
125. 6-inch Boresight Mk 37 Mod 0-Installed 141
126. Cutaway-6-inch Boresight Mk 37 Mod 0 143
127. Breech End Housing Assembly 145
128. Eyelens Mount Assembly 147
129. Dove Prism Mount and Filter Mount Assemblies 149
130. Muzzle Assembly 149
131. 8-inch Boresight Mk 31 Mod 0 153
132. Optical Diagram-8-inch Boresight Mk 31 Mod 0 154
133. 8-inch Boresight Mk 31 Mod 0-Installed 155
134. Cutaway-Muzzle Assembly, 8-inch Boresight Mk 31 Mod 0 156
135. Cutaway-Breech Assembly, 8-inch Boresight Mk 31 Mod 0 157
136. Breech Assembly 158
137. Eyelens Mount Assembly 159
138. Dove Prism Mount and Filter Mount Assemblies 161
139. Crossline Lens Mount Assembly 162
140. Body Assembly 162
141. Muzzle Assembly 164

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