Hoffman Amplifiers Tube Amplifier Forum
Other Stuff => Other Topics => Topic started by: kagliostro on July 19, 2015, 03:29:36 am
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A friend bought a telescope for his air rifle (an old Diana 50)
http://www.network54.com/Forum/79537/thread/1190567863/Diana+model+50-b (http://www.network54.com/Forum/79537/thread/1190567863/Diana+model+50-b)
he got it at an Ham Fest in Friedrichshafen and the price was very low
the riflescope is similar to this
http://www.ebay.it/itm/Brand-New-3-9x40EG-Rifle-Scope-with-Red-Green-Illuminated-Reticle-SALE-/141440398324?pt=LH_DefaultDomain_3&hash=item20ee8133f4 (http://www.ebay.it/itm/Brand-New-3-9x40EG-Rifle-Scope-with-Red-Green-Illuminated-Reticle-SALE-/141440398324?pt=LH_DefaultDomain_3&hash=item20ee8133f4)
it has a grid that I don't understand 100%, this one
(http://i.imgur.com/CI8g9e3.jpg)
I know the basic concept of the mil dot
(http://i41.photobucket.com/albums/e300/supv26/mildot1500yard21X.jpg)
but I don't know how to use this kind of grid, is the "V part" relative to the deviation drift due to the rotation of the bullet ?
Someone can explain it to me or give a link to a tutorial ?
Thanks
K
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https://en.wikipedia.org/wiki/Stadiametric_rangefinding (https://en.wikipedia.org/wiki/Stadiametric_rangefinding)
(http://upload.wikimedia.org/wikipedia/commons/thumb/d/da/M67_sight_full-stadia_picture.png/200px-M67_sight_full-stadia_picture.png)
While your air-gun is not likely to be sighting armored tanks, I suspect there is some standard-size target used for small-gun range finding. If it looks as wide as the top line, you aim a little high. If it looks as small as the bottom line, you aim a lot high.
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I have a "transit", a telescope on a tripod with precision angles, and a rod marked in feet/inches (metric would be better).
(http://imavex.vo.llnwd.net/o18/clients/runyonrental/images/5856.jpg)
http://www.runyonrental.com/LEVEL-TRANSIT-WTRIPOD-amp-STICK.item (http://www.runyonrental.com/LEVEL-TRANSIT-WTRIPOD-amp-STICK.item)
(Mine is much older, no plastic.)
It does many things, and it does "stadia (https://en.wikipedia.org/wiki/Stadia_mark)".
A Greek stadion was 600 feet. This was often used to measure roads (road-builder's payment, army travels).
My transit's stadia marks are "100:1". If my 6-foot assistant's head and shoes just fit between the stadia marks in my transit's grid, he is 600 feet away.
In modern road-building we need sticks in the ground every 100 (curves) or 1,000 (straights) feet. Instead of finding a 6-foot assistant, I look at the marks on the rod my helper holds (actually I strap the rod to a tree). If the stadia marks cover 1 foot of the rod (say, 4'3" to 5'3") then I am 100 feet from the rod; 10 feet, then I am 1,000 feet from the rod.
It would be more precise to use a survey chain (a very fancy tape-measure). However in road-building, the road goes from end to end, and we just need a lot of roughly 100 or 1,000 foot intervals to place marker sticks for the bulldozers and pavement machines. We only need to stay very-near the intended route (not drift onto private property). Apparently stadia-marks in transits "can" give error of 1 in 400, which is better than bad chain-work (it is hard to hold a tape/chain *exactly* straight over long distances). Stadia-estimation is much faster than dragging a chain.
Of course when shooting you can't send a boy to the target with a calibrated rod. Your question is: what is the intended target-size for this scope? In military small-arms it would of course be the size of a human. But overall standing in the clear? Just chin-to-helmet peeking over a hill? And this V-grid seems to go by width, not height.
And the "drop" for a given target and a given grid will be very different for a 30-06 war-rifle or a hobby air-rifle. When I used to shoot over 100 feet, the 30-06 went right-on, the .22 dropped several inches.
If you are target-shooting: sand-bags, measured range, and a lot of shooting will tell you how much drop to expect for how the target looks against the V-grid. But of course in target-shooting you probably already know the range, and how much drop your gun gives at that range.
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Many Thanks PRR
Franco
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https://www.google.com/search?q=how+to+use+rifle+scope+range+finding+graph&biw=1280&bih=558&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCoQ7AlqFQoTCNagpJLg8sYCFYlyPgodPt4Blg#tbm=isch&tbs=rimg%3ACfxQDldQNBfEIjhgz-E3y5YqObZCy675tExFlaQfEgC8RRSG7jslOgN244UXA2wnLdJyDwMzI3LjKortvavd5tmC0SoSCWDP4TfLlio5EXKk8L4mSPuNKhIJtkLLrvm0TEURffPR7I411w8qEgmVpB8SALxFFBG51UgUaBZpiioSCYbuOyU6A3bjEYWG3SziP761KhIJhRcDbCct0nIR5DQ44WHfbYIqEgkPAzMjcuMqihEWpw3BpR76qCoSCe29q93m2YLRESL4Q-oaL82l&q=how%20to%20use%20rifle%20scope%20range%20finding%20graph (https://www.google.com/search?q=how+to+use+rifle+scope+range+finding+graph&biw=1280&bih=558&tbm=isch&tbo=u&source=univ&sa=X&ved=0CCoQ7AlqFQoTCNagpJLg8sYCFYlyPgodPt4Blg#tbm=isch&tbs=rimg%3ACfxQDldQNBfEIjhgz-E3y5YqObZCy675tExFlaQfEgC8RRSG7jslOgN244UXA2wnLdJyDwMzI3LjKortvavd5tmC0SoSCWDP4TfLlio5EXKk8L4mSPuNKhIJtkLLrvm0TEURffPR7I411w8qEgmVpB8SALxFFBG51UgUaBZpiioSCYbuOyU6A3bjEYWG3SziP761KhIJhRcDbCct0nIR5DQ44WHfbYIqEgkPAzMjcuMqihEWpw3BpR76qCoSCe29q93m2YLRESL4Q-oaL82l&q=how%20to%20use%20rifle%20scope%20range%20finding%20graph)
http://www.opticstalk.com/39x40-ir-rangefinding-graph-reticle_topic23116.html (http://www.opticstalk.com/39x40-ir-rangefinding-graph-reticle_topic23116.html)
http://www.ifish.net/board/showthread.php?t=99842 (http://www.ifish.net/board/showthread.php?t=99842)
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Many Thanks also to you JJasilli
Franco