May 29th, 2012

Gottfredson Articles in FREE Digital Edition of GUNS Magazine

600-yard Card Fun Shoot Jacob GottfredsonThe June Digital Edition of GUNS Magazine is now available for free online. Just click this link to view the June Edition. NOTE: When the log-in screen appears, simply click the “CONTINUE” button. You do NOT have to fill in your name or email address. You can also read previous monthly editions by clicking on the Archive Tab. The last three (3) years of GUNS Magazine can be accessed for FREE online.

Articles by Jake Gottfredson in June Edition
The June Edition of GUNS Magazine contains two interesting articles by our friend (and AccurateShooter contributing writer) Jacob (“Jake”) Gottfredson. In the first article, Some Basic Riflescope Theory, Gottfredson identifies key principles of optics and shows how they apply to riflescope design and construction. He explains the term “Modulation Transfer Function” (MTF), and how this can be used to quantify both contrast and resolution. The author also explores the topics of color correction, chromatic aberration, and color fringing. Jake notes how color correction and focus precision are directly related. Jake also explains the difference between “clarity” and “resolution”. You can have a scope with good clarity but poor resolution or vice-versa. If a scope shows cloudiness it lacks clarity. If the scope can’t show a test grid in sharp focus, it lacks resolution. There are many other important insights Jake provides in this well-written article. We recommend you read the article and perhaps event print it out for future reference. If you are shopping for an expensive scope, Jake provides specific criteria by which you can judge a scope’s quality and repeatability.

Riflescope Optics Gottfredson

600-Yard Playing Card Shoot — Tiny Target, Far Away
The second offering by Gottfredson in the June issue of GUNS Magazine, is an entertaining report about a 600-yard fun shoot using playing cards. Regular-sized 2.5″ x 3.5″ playing cards with a 3/4″ red dot are placed in the center of an 8.5″ x 11″ target sheet. To help aiming, the target sheets have a black ring about 5″ in diameter. After a sighter session, shooters are allowed 10 shots in 7 minutes from 600 yards. That’s a pretty tough challenge, but with a very accurate rifle, multiple card hits are possible. Jake reports that, at his “card shoot”, the two top competitors, Gary Chaney and Andrew Smith, each hit the card six (6) times, with Gary breaking the tie by hitting the 3/4″ red dot. If this sounds like fun, read the full story, and perhaps you can set up a similar match at your shooting club. Gottfredson even includes “10 Tips for Success” such as: “7. Shoot fast, trying to get all rounds downrange in the same wind. Stop when it changes and wait for it to return or hold off if it does not….”

600-yard Card Fun Shoot Jacob Gottfredson

In addition to two Gottfredson articles, the June Edition of GUNS Magazine has a helpful feature on the .243 Winchester by John Barsness. This provides a short history of the cartridge and Barsness discusses 6mm bullet options for hunters using the .243 to harvest game.

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May 29th, 2012

Wind-Reading LaserScope Patented by Israeli Nuke Lab

Imagine a “smart scope” that can range your target AND calculate windage correction. Such technology may appear in riflescopes fairly soon. The Israeli Government’s Soreq Nuclear Research Center has received a U.S. patent for a new laser-based technology that can gauge wind vectors as well as target distance, using a laser rangefinder coupled to a rifle-scope. The Israeli system is called LIDAR, an acronym for Laser Identification Detection And Ranging. This new technology could, potentially, be a major boon for long-range shooters, both military and civilian. Ironically LIDAR was first developed for environmental monitoring (not for use with weapons). A LIDAR system was used for 3-D mapping and modeling of wind-driven plumes from the Israel Electric Company’s Rabin power plant.

Credit The Firearm Blog for breaking this story on the new Israeli LIDAR technology for sniper scopes. Below you’ll find the LIDAR Patent Application Abstract, which has a good summary of how LIDAR reads the wind.

The new Israeli LIDAR unit gauges wind speed by detecting fluctations in laser signals sent out from the integrated scope/LRF, reflected back from the target, and then received by photodiodes in the scope/LRF. Other scopes have used built-in LRFs to measure distance-to-target, but Israel’s patented LIDAR goes one step further, using the laser to gauge BOTH target distance AND wind vectors (i.e. velocity + direction). This information is entered automatically into software. The software then calculates a ballistic solution compensating for distance, wind angle, and wind velocity. If it really works, LIDAR represents a remarkable technological achievement. The Israelis claim LIDAR works for targets at distances of 500m or greater. Why won’t it work at closer ranges? Presumably the wind-induced laser fluctuations are too small to register at closer distances.

Current Integrated LaserScopes for Hunters
While the Israeli LIDAR system may seem like science fiction, it’s not that far removed from the lastest commercial optics. Engineers on both sides of the Atlantic have already integrated laser rangefinders (LRFs) into rifle-mounted “consumer” optics. Just this year, Burris introduced an affordable “consumer” scope, the Eliminator, that ranges the distance to target and then displays the ballistically correct aiming point on the vertical crosshair. The amount of hold-over is automatically calculated with reference to ballistics formulas. At right is a view through the Burris Eliminator; the illuminated dot shows the calculated aiming point.

While such technology can help a shooter compensate for bullet drop, windage compensation is another matter. A shooter must still gauge crosswind angle and velocity, and then hold left or right accordingly. If the LIDAR system can perform this task reliably, that is a major advancement.

DARPA “One Shot” System to Have Wind-Reading Capability
Meanwhile, in the United States, the Defense Advanced Research Projects Agency (DARPA) is proceeding forward with a One-Shot Sniper System, another “Super-Scope” that will have day/night capability, and calculate both elevation AND windage correction automatically. Prototypes have already been tested, demonstrating that a laser beam can be used to “measure the average down-range crosswind profile”. The wind data is combined with readings of temperature, humidity, and target range to provide a very sophisticated ballistic solution. DARPA’s Spec for the One Shot program calls for a 12-42X Direct View Optic (DVO), a Riflescope Display Assembly (RDA), and an Integrated Spotting Scope (ISS) with rangefinder that ranges to 2 km, and provides “crosswind measurements”. The system will be “menu-selectable” for .308 Win, .338 Lapua, and .300 Win Mag. DARPA has budgeted big bucks for the One Shot system. The ISS, by itself, is expected to cost $85,000 per unit (for the first 15 units).

These systems will never replace the utility of an experienced shooter who possesses the skills of wind reading, but it is a real boon for less experienced shooters. In terms of military utility, it is a game changer. I’ve seen and used a prototype of the One Shot, and it does perform as advertised. — SFC Emil Praslick III, USAMU Coach

Can Wind-Reading Systems Work in the Real World?
From what we can tell, the LIDAR system, and America’s competing One Shot System, are both designed to measure crosswind speed and angle AT THE TARGET primarily. But as any experienced long-range shooter knows, wind is rarely constant along the entire path of the bullet. There can be a 10 mph left wind near the firing point, a 5 mph tailwind in mid-trajectory, and a 20 mph right wind 1000 yards away. Importantly, wind close to the shooter has more effect on the bullet’s path than wind far downrange — that’s a matter of simple geometry. Therefore, any wind-reading system could provide incorrect solutions if it is not able to read and calculate different wind vectors along the full bullet flight path. Presumably LIDAR and One Shot systems will attempt some kind of crosswind averaging, but that will be a very challenging task, without multiple wind sensors downrange.

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