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TELESCOPIC SIGHTS
Telescopic sights may be categorized as "Outside Adjustable" and "Internally Adjustable."
Outside adjustable telescopic sights include Lyman Targetspot and Super Targetspot, Unertl, Litschert, Fecker and Davis brands. These have adjustments built into the mounts that are (mostly) click adjustable and clearly readable so that settings may be recorded. They have adjustments on the rear for focusing the crosshairs, and on the front (Fecker in the center) for eliminating parallax. It is entirely practical to move these sights from rifle to rifle, re-setting the sights each time.
These sights attach to "scope blocks" on the rifle barrel, which are most often 7.2 inches on center.
The adjusting knobs are marked in 25 divisions, and there is a click between each division, so there are 50 clicks per revolution of the knob. Each click moves the telescope one-half of one thousandth of an inch, .0005". Divide 3600 inches in 100 yards by 7.2 inches center distance between scope blocks and you get 500. Then multiply 500 by .0005" per click and you get .250" or a quarter inch or about a quarter minute of angle shift in bullet impact per click.
Sometimes scope blocks are mounted on centers other than 7.2 inches, and bullet movement at 100 yards varies as shown below:
Scope Block Centers 100 Yard Movement per Click
2.4 inch .75 inch
3.0 " .60 "
3.6 " .50 "
4.5 " .40 "
6.0 " .30 "
7.2 " .25 "
9.0 " .20 "
12 " .15 "
Trouble with a Lyman Super Targetspot
I was working with an M54 Winchester in 30 WCF = 30/30 and a Lyman 30X Super Targetspot (STS) in the summer of 2005 when I ran into trouble. While groups were averaging about an inch and a quarter, every now and then a shot was missing. After taking advice and shooting at the center of a big target, I found that sometimes a shot showed up from three to ten inches low at 100 yards. These strangers were a puzzle.
I cleaned the gun without finding anything unusual in the barrel.
This is an old telescopic sight, most of the blue has been replaced by that much-desired "patina". I got after that patina with some 0000 steel wool and oil. Nothing looked any different when that was complete, the patina was still there. (Every time I shoot using a telescope, I wipe the scope down with an oily cloth.)
Then I took the rear mount , the one with the adjustment knobs, off the scope and cleaned it. I took it apart, took the spring loaded 225 degree doodad off and apart, took the adjustment knobs off and the Chinese-character looking metal parts out. I cleaned and oiled the dickens out of the parts, and put it back together-not too hard. A toothbrush and some 3 in 1 oil and some clean rags did the job. There was quite a bit of stuff in there, dirt or old oil or ?
Back at the range many times since, many shots fired and not a stranger to be seen.
I think it was the scope, I think that some speck/s of stuff got in the workings and caused the very low shots.
Another problem with the Lyman Super Targetspot
I record the sight settings with information on the gun, load, distance and scope or iron sights, in my notebook. I have noticed that I have made many one-revolution mistakes when recording settings on a Lyman Super Targetspot.
Now I sort of understand why this happens and it's because of the design of the micrometer. I can only advise you to fiddle with the micrometer a while and get a good notion of what various settings look like and be careful when recording settings. It isn't you.
From the book.
joe b.
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One Scope on More Than One Rifle (Read 5705 times)
