1 MATHEWS, J. H., and HENKE, LEE K. The Comparison Camera. Jour. Crim. Law and Criminology 37: 247 (1946).

2 MATHEWS, J. H., and HENKE, LEE K. The Rifling Meter. Ibid. 35: 134 (1944).

3 BRADFORD, L. W., and BRACKETT, J. W. R. Identification News. March 1953.

4 MUNHALL, B. D. Proceedings of the I. A. I. 1950 (pp. 166-171).

Fig. 45. Early type comparison microscope. Employed by Albert S. Osborn for document examinations. Constructed by Bausch & Lomb.

Fig. 46. Diagram illustrating tli principle of the comparison microscope. (Schematic illustration by Burton D. Munhall, courtesy of the Institute of Applied Science, Chicago, 111.)

Fig. 47. Bausch & Lomb comparison microscope. (Early type.) This instrument obtained by author in 1925 on special order. A similar microscope had been made by B & L for Professor Chamot of Cornell University for his study of primers during World War I.

Fig. 48. Leitz comparison microscope made by E. Leitz, Wetzlar, Germany.

Fig. 49. Bausch & Lomb comparison microscope. A later type. Illumination is from a single lamp rather from individual spot lights whose position and intensity can be adjusted. Such flexibility is desirable.

Fig. 50. Bausch & Lomb microscope and camera. Same microscope as shown in Fig. 49 but with addition of camera.

Fig. 51. Bausch & Lomb comparison microscope. Modern type. (Photo by courtesy B & L.)

Fig. 52. Spencer comparison microscope. (Photo courtesy American Optical Co.)

Fig. 53. An early case of matching of rifling marks by means of the comparison microscope. Photograph taken by Goddard subsequent to the trial of Sacco and Vanzetti, while case was being reviewed on order of the Governor. Comparison microscope photographs and comparison microscope testimony not used at the trial. Much of the testimony was very unscientific and irrelevant.

Fig. 54. Comparison microscope matchings. Test bullets above horizontal line, evidence bullets below line. Four different cases.

Fig. 55. Matching of rifling marks.

Left: Matching of marks made by land.

Above line: Test bullet from suspect gun.

Below line: Fatal bullet.

Right: Matching of marks made by groove.

Above line: Test bullet from suspect gun.

Below line: Fatal bullet.

Note: All six lands and grooves could be matched.

Fig. 56. Matching of rifling marks (comparison microscope photos). Above line: Rifling mark on test bullet fired from suspect gun. Below line: Rifling mark found on evidence bullet.

Fig. 57. Comparison microscope photograph. Showing matching of rifling marks on a tiny fragment of bullet jacket taken from victim's kidney by surgeon (upper) with marks produced on a test bullet (lower) fired from suspect's gun. This tiny portion of the copper jacket was all that was found, the remainder having been torn off in passing through the side of an automobile.

Fig. 58. Comparison microscope photographs. Showing matchings on two pairs of bullets. Two different guns.

Fig. 59. Lines on deformed bullets fail to match. While the matching of the test (upper) bullet with the evidence bullet (lower) is good in each case in the center part of the photos, it will be noted that the lines become farther apart on the evidence bullet, due to its expansion. This is a common occurrence with evidence bullets that are deformed, as they so frequently are. (Note: Bullets were fired from different guns.)

Fig. 60. Matching of breechblock marks (comparison microscope photos). These are matches obtained in three separate cases. In each case, test shell is above line of separation.

Fig. 61. The comparison camera. Used particularly for the examination, comparison, and photographing of fired bullets.

Fig. 62. Comparison camera. Same as Fig. 63 but from different angle.

Fig. 63. Comparison camera. Showing forward assembly all of which is mounted on a block which slides forward or back to accommodate lenses of different focal length.

Fig. 64. Comparison camera. Showing detail of mechanism for rotating bullets.

Fig. 65. Rear end of comparison camera. Bullets may be moved in three dimensions and rotated by turning lettered knobs. Bullet images are necessarily dim in this photo as the lights were on in the room in order to take the picture.

Fig. 66. Comparison camera photographs. Showing the matching of the same pair of bullets in three successive positions. Above line: Test bullet. Below line: Fatal bullet. (.25 cal. metal-jacketed bullets.)

Fig. 67. Comparison camera photograph. Showing matching of two bullets fired from a .32 cal. Savage automatic pistol. Reproducible markings on lands as well as in the grooves. jacketed bullets often do not show good markings on lands.

Fig. 68. Comparison camera photograph. Showing matching of two bullets fired from a .38 cal. revolver.

Fig. 69. Comparison camera photograph. Shows matching of two bullets fired from a .38 S&W Special revolver.

Fig. 70. Comparison camera photographs. Four successive matchings on a pair of lead bullets fired from a .38 cal. revolver whose cylinder did not line up properly with the bore of the barrel, causing the shaving of lead. This is a frequent occurrence with poorly-made guns and sometimes with guns of good make which have become badly worn. Test bullet above line. Evidence bullet below line.

Fig. 71. Matching of .22 Short bullets (comparison camera, 60 mm. lenses). The matching of .22 Short bullets is usually a difficult matter and, as in this instance, the results are often inconclusive. Often the bullets will show few if any distinguishing rifling marks and all too frequently they are so deformed that even a comparison of widths of rifling marks may not be satisfactory. This was not the case here.

Fig. 72. Comparison camera photograph. Showing four matchings obtained on a pair of .22 cal. lead bullets. Above line: Test bullet. Below line: Evidence bullet.

Matchings of this quality on .22 cal. lead bullets are rare. This is due to their small size, the softness of lead, the low powder pressures used, and the fact that arms of this caliber are often not cared for properly and are likely to have rifling which is worn, rusty, or leaded.

Fig. 73. Comparison camera photograph. Evidence bullets are often badly deformed. This makes identification difficult and sometimes impossible. In the case illustrated, however, it was possible to get a quite satisfactory matching of the test bullet (upper) with the fatal bullet (lower).

Fig. 74. Comparison camera photograph. Showing matching of breechblock markings on primer of a fatal shell (below line) with markings on primer of a test shell (above line) fired from suspect's gun.

Fig. 75. The rifling meter. For measuring the pitch of rifling in rifled barrels.

Fig. 76. Dial, vernier, and reading lens. Lens swings on an are. Dial calibrated 180° right and 180° left.

Fig. 77. Auxiliary clamping device for barrels having extreme taper or unusual shape.

Fig. 78. Lead disk-cutter press and dies for cutting lead disks used with the rifling meter.

Fig. 79. Assembly of apparatus for measuring pitch of rifling on a fired bullet. This is useful only in case the bullet is in near perfect condition.

Fig. 80. Apparatus for measuring angle of rifling pitch from a fired bullet. (An alternate method.)

Fig. 81. Diagram illustrating the principle and technique involved in the determination of the angle of rifling from measurements made on a fired bullet. This reticle (grid of fine parallel lines) is in the eyepiece of the microscope. The angle of rifling is determined by lining up a groove edge with one of the parallel lines and then lining up the sides of the bullet with others of the parallel lines. The amount that the bullet has to be turned to do this represents the angle of the rifling. The lines of the grid are actually much finer than those shown in this illustration.

Fig. 82. Measurement of rifling angle on fired bullet. Showing quartz fiber mounted in fixed position directly above the bullet and in exact line with the axis of rotation of the screws that hold the bullet in position.

The bullet is rotated by turning the knob at the extreme right, and the „driving edge" of each land impression is brought directly under the quartz fiber before any settings are made.

After determining the exact position of the quartz fiber, and thus determining the reference axis, measurements of the angle between the land impression and this axis are made for each land impression on the bullet. The average of these values is used in computing the length of barrel required for one turn of the rifling.

Fig. 83. Leitz instrument for measuring rifling angle. (The author has had no experience with this instrument and therefore is not qualified to pass judgement on it.)

Fig. 84. Leitz instrument for measuring width of lands on fired bullet.

Fig. 85. Complete assembly of apparatus for measuring groove widths on fired bullets. Greenough type binocular microscope on rotatable table, device for holding bullet and measuring groove width, and two-tube fluorescent lamp (Burton).

Fig. 86. Device for holding bullet and for measuring width of grooves on a fired bullet. Slide carrying bullet mount moves to right or left as Starrett micrometer spindle is rotated. Lens enables operator to make accurate readings from microscope eyepiece level.

Fig. 87. Slippage marks. Bullets fired from revolvers are particularly likely to show slippage marks such as shown here. The bullet, already having attained a high velocity before striking the lands, resists taking a rotational movement because of its inertia. This results in a double impression of the lands. The proper width to measure is indicated by the arrow between the two parallel lines. This represents the width of the land that made the groove.

Fig. 88. Lead disk on end of „thrust rod" after being forced through a rifled barrel, in operation of the rifling meter.

Fig. 89. Set of Starrett Small Hole Gauges, modified as described in the text. Used for measuring bore and groove diameters of rifled barrels.

Fig. 90. Enlargement of three gauges shown in Fig. 89. Left: Unmodified gauge. Center: Two ,fins" (for even number of grooves). Right: One „fin" (for odd number of grooves).

Fig. 91. Diagram of modified Starrett Small Hole Gauge, with two „fins," for measuring groove diameters when number of grooves is even.

Fig. 92. Diagram of modified Starrett Small Hole Gauge, with one „fin," for measuring .groove diameters" when number of grooves is odd.

Fig. 93. Set of tapered gauges. Used for measuring bore diameter of guns having an odd number of grooves. Taper is such that there is a difference in diameters of ca. 0.020" at the two ends of the taper. Complete set consists of 13 gauges.

Fig. 94. Micrometer stand, a simple and convenient device for holding the micrometer so that one may have use of both hands for manipulation.

Fig. 95. Photography of hand guns. Equipment used by the author for photographing hand guns. It is described fully in the text.

Fig. 96. Illustrating importance of proper placement of scale in gun photography. The upper scale was 11/16" closer to the camera. Scale should be supported so that it is at the same level as the bore of the barrel.

Fig. 97. Better photographs of rusted nickel-plated guns can be made by first dusting with aluminum powder.

Fig. 98. Stereocamera on binocular microscope. Shows a rifle shell head being photographed. As set up here the head of the shell is illuminated with a Silverman Illuminator (large size), which gives even illumination from all directions.

Fig. 99. Stereophotomicrographs. The binocular microscope, which gives a three-dimensional view of an object, is indispensable. To make a permanent record of what the binocular microscope reveals, a threedimensional photograph is necessary. Above are examples of such photos. To bring out the third dimension they must be viewed with a stereoscope.

Fig. 100. Stereophotomicrographs. Showing breechblock markings on two shells fired in the same gun. To bring out the third dimension these must be viewed with a stereoscope.

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