GUNS AND AMMUNITION. 



Anybody can keep on shooting all day, but it takes a gentleman to quit when he gets enough. 



SEMI^TELESCOPIC SIGHTS. 

 Pot a year or 2 past, there has been a 

 remarkable revival of interest in optical 

 aids to the rifleman, for more surely di- 

 recting rifle shots. The market is now 

 well supplied with rifle telescopes; some 

 good, some indifferent. They are not un- 

 reasonably expensive ; yet to a large num- 

 ber of users of the rifle, the cost is so 

 much of a bar that they deny themselves 

 the pleasure and comfort a good 'scope 

 can undoubtedly afford. There is, beside 

 the reguler telescope with metallic tubes, a 

 contrivance composed of 2 spherical lenses, 

 1 for the eyepiece, and 1 for the ob- 

 jective, using no tube or diaphragm. This 

 is denominated the semi-telescopic, or lens 

 sight, and will, when properly constructed, 

 furnish a cheap and useful substitute for a 

 telescope. In' various forms they have been 

 in use many years, and there is some 

 question as to who first devised them. In 

 their simplest form, of which we shall here 

 treat, they can be practicably made by any 

 one possessing average mechanical skill. 



The lenses can be obtained of any optician 

 or jeweller, and should be cut by him and 

 ground to proper diameter from an ordinary 

 first quality, centered spectacle lens, care 

 being taken that the center of the original 

 lens be also the center of the new lens. 



The front lens, the objective, is a plus 

 or convex glass, and is preferably mounted 

 in some form of a hood or globe sight. In 

 the ordinary sight of this kind, the lens 

 may be easily fixed so that it can, at will, 

 be inserted or removed. The cell to con- 

 tain the lens may be made of brass or hard 

 rubber tubing, or the lens may accurately 

 fit the inside of the hood sight, and be 

 held in by 2 incomplete rings of spring 

 brass, one on each face of the glass. The 

 pinhead or aperture of the front sight re- 

 mains unaltered, and is used the same as 

 though, no lens were employed. It is ne- 

 cessary, if good work is to be done, to have 

 the objective well within the hood, so that 

 the side rays of light may be cut off en- 

 tirely. It might be mounted on a combi- 

 nation front sight, like the Beach or Lyman, 

 if the lens were protected by a supplemen- 

 tary tube, with the same end in view: 

 cutting out all side light. 



The rear lens, the eyepiece, is a minus 

 or concave glass, 'and should be mounted 

 in the eyecup or aperture of the peep sight, 

 taking care that the optical center of the 

 lens and the center of the aperture in the 

 disc coirrcide. This lens may be temporari- 

 ly mounted in sealing wax, used to make it 

 adhere to the rear side of the cup. An 



excellent method is to have 2 interchange- 



able cup discs, one with the eyepiece per- 

 manently attached, and the other one plain. 



The strength of the lenses depends upon 

 2 factors; the distance between sights and 

 the power required of the completed sight. 

 All users of this device agree that the best 

 results are obtained with the lower powers, 

 nothing higher than 4 powers being per- 

 missible, and the best being 2 powers. This 

 latter reduces the apparent distance to the 

 target just J^, with all the consequent ad- 

 vantage. 



The principal reasons for keeping the 

 power low are 2. First, the size of field is, 

 owing to construction, necessarily limited, 

 and decreases rapidly as power is increased. 

 Second, the principal use of a rifle thus 

 equipped, being for off-hand work, the 

 power must be low, or the magnification of 

 the errors in holding would be so great that 

 it would be almost impossible to use it in 

 strictlv off-hand work. Few men can 

 use a power higher than 4 or 5 diameters 

 in off-hand work, even if equipped with a 

 telescope of high grade, good illumination, 

 c.zi6. large field. 



In using the semi-telescopic sight in tar- 

 get shooting, many who have impaired vis- 

 ion find it the one thing needful to perfect 

 their scores, and to anyone, the regulation 

 bull's-eye at 200 yards is a very different 

 shooting proposition than when viewed with 

 naked, unaided eye. It apparently has in- 

 creased in size to twice its former dimen- 

 sions, assuming that your lens sights are 2 

 power, and you may still use your favorite 

 pinhead or aperture front sights, unim- 

 peded as before. 



As I have said, the strenrth of the 

 lenses depends on 2 factors ; the distance 

 between sights, and the power required. 

 Now as to the formula to obtain the proper 

 foci of the lenses. Let d. represent the dis- 

 tance between sights, and p. be the power 

 required. Then d. divided by (p. minus 1). 

 expressed thus — , will be the focal 

 strength of the eyepiece or rear lens, which, 

 of course, is a concave glass. The front 

 lens, the objective, will be a convex glass, 

 equal in power to the focal strength of 

 the eyepiece, multiplied by the power re- 

 quired. 



For example, if the distance between 

 sights is 31^ inches, and we desire to con- 

 struct a 2-power sight, then 515= 31 - 5 (con- 

 cave), this being the focal strength of the 

 eyepiece. 31.5 multiplied by 2, the power 

 required, = 63. (convex), which is the focal 

 strength of the objective. These focal 

 strengths are expressed in the nearly obso- 

 lete, so-calJeq! inch system, For convenience 



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