TECH TIP: Picatinny vs. Weaver Rail Specifications

Readers often ask “What’s the difference between a Weaver scope rail and a Picatinny Rail?” The answer is not as simple as it seems. The dimensions of a Picatinny Rail should be consistent (from one rail-maker to another), since there IS a government spec. Conversely, there is some variance in “Weaver-style” rails. The width of the groove is the most important difference between Picatinny Rails and weaver rails. “Mil-spec” Picatinny rails will have a grove width of 0.206″ while Weaver rails typically have a narrower, 0.180″ groove width.

Brownell’s has a helpful BenchTalk Article that discusses the Picatinny Rail vs. Weaver Rail. That article explains:

“What are the differences between the ‘Picatinny’ and the ‘Weaver’ systems? The profile of the two systems is virtually identical. Depending on the quality of the machining done by the manufacturer, the two systems should be indistinguishable from the profile. The key difference lies in the placement of the recoil grooves and with width of the grooves. MIL-STD-1913 (Picatinny) grooves are .206″ wide and have a center-to-center width of .394”. The placement of these grooves has to be consistent in order for it to be a true ‘Picatinny’MIL-STD system. Weaver systems have a .180” width of recoil groove and are not necessarily consistent in a center-to-center measurement from one groove to the next.

In many instances, a Weaver system has a specific application that it is machined for, so interchangeability is not necessarily an issue. A MIL-STD-1913 system must adhere to the specifications listed above in order for it to be considered MIL-STD, since the military desires uniformity in the recoil grooves to allow for different systems to be mounted on the weapon with no concern for compatibility.

Now, what does this mean to you? Boiled down, it means that accessories designed for a Weaver system will, in most cases, fit on a ‘Picatinny’ system. The reverse, however, is probably not the case. Due to the larger recoil groove, ‘Picatinny’ accessories will not fit a Weaver system. There are, of course, exceptions to every rule, but for a good rule-of-thumb, [full-width] ‘Picatinny’ won’t fit Weaver, but Weaver will fit ‘Picatinny’.”

Lapua Offers Radar-Tested Drag Data for Lapua Bullets

The Ballistic Coefficient (BC) of a bullet is an index number used to describe the bullet’s aerodynamic drag relative to a reference standard. While bullet manufacturers commonly include BCs in their product descriptions, often times those numbers are merely a mathematical calculation, rather than the result of actual testing. Also, since the true drag of a bullet changes over the course of its trajectory, using a single BC is a fairly primitive way to predict how that bullet will actually perform over a long distance.

Lapua is now using Doppler radar to provide a more sophisticated model of bullet flight. Lapua has issued drag coefficients for its bullets based on radar testing. Importantly, Lapua didn’t just calculate drag coefficients off bullet blueprints. Instead, Lapua used radar to measure bullet velocities at various points along the bullet flight path (trajectory). This provides Cd (Coefficient of Drag) values that can be used with advanced ballistic software such as QuickTARGET to calculate trajectories with great reliability and precision.

Lapua’s engineers explain: “With our Cd-data measured by continuous Doppler radar measurements you can calculate the trajectory of your bullet much more accurately than using the simplified one-number BC. Typically-used simple ballistic coefficient (BC) describes only ballistic performance of the bullet compared to old standard ‘G1′ bullet. Ballistic Coefficient is essentially a measure of drag force compared to G1 projectile. The higher the BC value, the less drag and better ballistic performance.

The BC changes during a projectile‘s flight and stated BCs are always averages for particular velocity ranges. Knowing how a BC was established is almost as important as knowing the stated BC value itself. For the precise establishment of bullet trajectory, Doppler radar-measurements are required. The normal shooter however, has no access to such expensive professional measurement devices.

The radar-measured Cd factor describes the aerodynamic drag at particular points of trajectory. A Cd table (see above) shows this factor as a function of velocity (Mach number). Special software is required (e.g. Quick Target Unlimited) to utilize this data to [generate a] ballistic table. During the Doppler radar measurements the complete location information versus time is recorded.”

Long-Range Tests Show Lapua’s Bullet Drag Models Work Well
One of our sources has been working with Lapua’s radar-derived ballistic data for over a year. His task was to see how calculated trajectories using Lapua’s stated Cd values for particular bullets compared to observed bullet flights at long range. Using the data for the Lapua 250gr Scenar, this tester found the predicted trajectory “dead on to 1600 meters (about a mile) and only a few click off [at] 2000 meter (1.25 mile) distances”.

Bullet Ballistic Info for Download

CLICK HERE for explanation of Doppler-derived Cd with sample charts.

CLICK HERE for Cd-data for Lapua bullets.

New Enhanced Website for March Scopes

March scopes (built by Japan’s Deon Optical) have become extremely popular with short-range benchrest competitors, and we are seeing an increasing number of 600-yard and 1000-yard shooters upgrade to March scopes. The March product line offers high magnification (up to 60X power), a wide choice of reticles, and extremely bright, sharp lenses.

March has also quickly acquired a reputation for reliable tracking and shot-to-shot consistency. In the unforgiving short-range benchrest game, if your reticle shifts just a tiny amount from shot to shot, that can open up your group and drop you from a top place to “also-ran” status. Top short-range shooters have praised the March for its ability to “stay put” with no reticle movement, shot after shot.

New Website with All the New Scopes (with Specs)
In the USA, March scopes are sold by Kelby’s Inc., which has a page dedicated to March products on the www.Kelbly.com website. If you need MORE Information about the March scopes, there is now a new March Website, with more models, more photos, more data, and more reticle diagrams. You’ll find the latest Benchrest models on the new March website, including the new 36-55×52mm Benchrest EP Zoom Scope, the 10-60×52 Zoom, and the 40X, 50X, and 60X fixed-power BR scopes. In addition, the website features March’s new hunting and tactical series of optics, including the 1-10×24, 2.5-25×42 scopes which boast a revolutionary ten times Magnification Ratio.

NRA Shooting Sports Magazine Now Offered FREE Online

For years the NRA has published Shooting Sports USA, an informative print magazine for competitive shooters. While sample articles and a match calendar could be found on the web, the complete magazine contents were available only via a conventional print magazine subscription.

Now that’s changed. You can read ALL the contents of Shooting Sports USA now for FREE, in a monthly “Digital Edition”. Using “digital paper” technology from Olive Software, the entire magazine loads as a file in your internet browser. You can size the pages larger or smaller. You can even turn the pages as with a conventional magazine. To get your FREE subscription to Shooting Sports USA in digital form, just go to the Shooting Sports USA website, and enter your email address and zip code. That’s it — no fees, no credit card info required.

CLICK HERE to read a sample Digital Edition of Shooting Sports USA
(Note: This will load a flash player that may not be compatible with all browsers.)

Get New Rules, Match Results, Gear Reviews, and More…
The current issue of Shooting Sports USA includes the 2009 NRA Competitive Rule Changes. You can access those rule changes by viewing the March, 2009 sample digital edition (may take some time to load). Other features in the March edition include Shooters News, a Score Sheet (recent match results), Brief Product Reviews, and a Calendar of Coming Events.

Build a Simple, Portable PVC Target Stand

One of the easiest ways to build a portable target stand is to use PVC pipe and connectors. Utah .308 Shooter “Cheese” has created a simple yet sturdy target frame, and he’s shared his design so you can build a similar frame easily and at low cost. The components are wood furring strips, 2″-diameter PVC pipes (and connections), and a 2′x3′ sheet of cardboard. The PVC base can be glued together, or, for easier transport and storage, you can leave some or all of the connections free. “Cheese” tells us: “I didn’t glue any of it together so I could disassemble it, shove it in a bag and take it anywhere.”

“All the parts are just pushed together and not glued. That way I can break it down and carry it all in a bag. Also, if a buddy (not me!) happens to shoot the stand, I can easily replace just the damaged piece. The last 6 inches of the furring strips are wittled-down a bit so they can be pushed into the upright pipes with a little friction. The cardboard is 2 x 3 feet, and I use a staple gun to attach it to the furring strips. Then I just staple the target onto the cardboard and go at it.

Of course you can modify the dimensions as desired. I chose the black ABS pipe over white PVC simply for cost — black ABS is a little cheaper. You can also glue some or all of the parts together, it’ll just be larger for transporting. In windy conditions, the thing likes to come apart. Duct tape might work well. For weight, I thought about filling the two end pipes with sand and gluing test caps on each of their ends. The test caps still allow the pipes to slip into the elbows.”

Add Anchors or Internal Weight for Stability
On a very windy day, a PVC stand can shake or even topple over. There are a couple solutions to this. Some people fill the PVC pipe sections with sand to add weight, or you can put short sections of Re-BAR inside the long legs. One GlockTalk forum member noted: “I built [a frame] almost identical to this. I also take four pieces of wire coathanger bent into an inverted “U” shape to anchor the frame to the ground. It is so light that wind will knock the stand over [without anchors].”

Assembly Diagram with Dimensions
The photo below shows all the components of the base, with dimensions. The overall maximum assembled dimensions are roughly 26″ wide, 41″ deep, and 66″ tall (the cardboard is 2 x 3 ft).

You can find photos of a similar home-made PVC target stand (with a slightly different rear section) on the Box of Truth website. This also employs a PVC tubing base with wood uprights. We’ve also seen all-PVC target stands, but we’ve found that it is easier to attach the cardboard to wood strips than to PVC pipe. Also, if the upper section is wood, you can fit different height targets, while using the same base.

SEB Rest Update — New Model in Development

SEB coaxial front rests are impressively engineered and beautifully machined. If you like a joystick-style rest, you won’t go wrong with a SEB. This editor shoots off one. Though the current SEB rest is nearly ideal for short-range benchrest, shooters have asked for an upgraded version that can handle heavier rifles (such as 22-lb, F-class guns), and wider fore-ends (up to 6″). Sebastian Lambang, creator of SEB rests, has been listening, and he’s hard at work perfecting a new “magnum” model that will work with big, heavy guns. It is hoped that the new model SEB rest will be available in summer 2009, but it’s “too early to know for sure”.

2009 Update: New SEB Rest in Research & Development Report by Ernie Bishop, USA Dealer for SEB Products Seb’s goal is to make a new rest using an enhanced design (but it will still be a coaxial-type rest with double-sided functionality). It will have quicker elevation adjustment. It will also go lower and taller at the lowest & tallest setting (from about 4″ to 9″ tall, or more), and should accept rifle stocks up to 6″ wide. Here’s the good news — the price should be less expensive too. The new rest will still feature twin posts, with coarse elevation adjusted by rack & pinion. The center-to-center (“CTC”) between the posts is about 10″, to be able to accept rifle stocks up to 6″ wide. Like the current SEB rests, the new rest can be set up for either right-hand & left-hand shooters. The new rest should suit a broader set of disciplines — it will work for short range BR, F-class, long-range benchrest shooting, and varmint shooting, too. Unfortunately, because of the specifications/requirements, Seb must remove the “pivotal base system” and make the base in “T” shape. The base can be disassembled for easily for more compact storage. By design, the new model rest can accept a “Balance Weight System” (BWS) better than the standard SEB rest, because the weight (which is optional) would not interfere with the front elevation screw, the fore-end stopper, or the base. This is the reason that the new base will have be built with a “T” shape. The “BWS” is basically a counterweight, simply a chunk of stainless steel, attached on the side opposite side of the joystick. It’s an inexpensive, optional item, available in different weights. With the “BWS”, the SEB rests could accept rifles as heavy as 30 kgs (66 lbs.), or even more. This should be able to be accomplished without holding the joystick. If the weight is correctly matched to the weight of the rifle), I suspect that the rest top & “BWS” combination would remain stationary under hard recoil. Hopefully the new rest will cost less than the current model rest. Seb is trying to keep the price under $700. This should be possible because of changes to the design and materials. It will retain the same standard of smoothness and quality that Seb is known for. Finally, Seb asks for your patience. He is still evaluating materials and is still experimenting to determine what will work best. Besides this, Seb is working on an updated front bag design as well. (There is also an improved fore-end stop in the works.) Once this new rest is ready, Seb will be shipping some to the States for testing. Personally, I can’t wait to see this new rest! Ernie Bishop 306 West Flying Circle Drive Gillette, WY 82716 (307) 257-7431 ernieemily [at] yahoo.com

For more information on SEB front rests visit www.sebcoax.com, or contact Ernie Bishop (address above). Ernie notes: “I have a shipment of 15 rests coming toward the beginning of March. Currently, I am out of stock, and have started a waiting list. The USA price for a SEB Rest (including one 2.25” OR 3” front bag ) is $725.00 plus shipping/handling. Please don’t get confused by the price that is listed on Seb’s website. That price is for customers in countries where there are no SEB dealers.“

Magnetic Soft Vise Jaws

Here’s an handy and affordable product that everyone can use in their home workshop. When working with a vise you have to be careful not to mar or gouge the item you’re clamping. People will use cardboard, old carpet, even scrap leather as “padding”. All those options can work, but magnetic soft vise jaws are a simpler solution. These come in matching sets, sold for $12-$20.00 by a variety of vendors. Measuring 4-6″ long these have an upside-down L-shaped cross-section. The are formed from a semi-soft polyurethane that won’t scratch metal (or gouge wood). Simply mount the plastic pieces over the metal jaws of your vise. The soft jaws are held in place by magnets embedded in the backside of the plastic. If you wish, you can saw off the ends of the soft jaws for a better fit on smaller vises.

In todays’ report, we highlight two kinds of soft vise jaws, one with pre-formed channels and the other with flat edges. The first unit, made by Wilton, is bright yellow, with shaped channels to hold various items. Shown below, these soft jaws will hold Wood, Metal, Tubing, and more. The Wilton jaws cost $13.69 at TrueValue Hardware stores (item 606400).

For those who prefer polymer vise jaws with a flat edge (no channels), Graham Tool Co. makes a nice set of Soft Vise Jaws, priced at $19.95. Graham’s bright red vise jaws feature a flat contact surface with shallow, diamond-pattern serrations. The Graham soft jaws feature powerful rare-earth magnets, so they secure to your metal vise more securely than most other types of plastic jaws.

NOT for Barrel Removal/Installation
Soft vise jaws can hold a barrel for fine work, such as engraving. However, they are not designed to resist large torque loads. Soft jaws are NOT suitable for barrel removal and installation. For those tasks, use a dedicated barrel vise with the appropriate clamping insert.

Freedom Hunters Organizes Hunts for U.S. Military Veterans

There are many television shows about hunting. But the Freedom Hunters series, we believe, deserves special recognition. Freedom Hunters arranges “once-in-a-lifetime” outdoor hunting adventures for American military combat veterans. Footage from these hunting trips, along with background stories on the service men and women chosen for the hunt, are packaged into weekly cable broadcasts. Click the image below to visit Freedom Hunters’ Video Archive. There, click on the “PFC Josh Reilly” link to view great clips from a Wyoming hunt.

Freedom Hunters Seeks Female Veteran for Wyoming Pronghorn Hunt
Freedom Hunters is looking to present an all-expense-paid Wyoming pronghorn hunt to a female veteran. Freedom Hunters producers are specifically looking for women who have served in Afghanistan or Iraq. The hunt will be guided by Llano Outfitters (Casper, WY, 307-235-4865), one of Wyoming’s premier elk, deer and pronghorn outfitters. The hunt will take place in late October 2009. Applications must be received by March 15, 2009.

The woman selected to participate in this hunt will receive gifts from product sponsors and will be featured on a future episode of the Freedom Hunters television show. Those interested in applying for this opportunity should apply via the Freedom Hunters’ Application Page on the web.

Freedom Hunters is a 501(c)3 charitable organization serving the American military family. It is dedicated to honoring those who protect our freedoms. For more information about Freedom Hunters Programs, visit FreedomHunters.org or e-mail info [at] freedomhunters.org. Freedom Hunters airs Fridays at 4:00pm MST on the Altitude Sports and Entertainment network.

$50.00 Factory Rebate on Sightron Big Sky Riflescopes

Throughout 2009, Sightron is offering purchasers a $50.00 rebate on Sightron SII Big Sky™ riflescopes. To qualify, just purchase any Sightron SII Big Sky™ Series riflescope before December 31, 2009. These scopes feature the ExacTrack™ windage and elevation system, a Broadband lens coating process, one-piece main tubes, and Sigtron’s Lifetime Warranty.

CLICK HERE for Rebate Application Form.

The Fine Print
This offer is valied in the USA only. Purchase of an SII Big Sky™ scope must be made between January 1, 2009 and December 31, 2009. To qualify for the rebate, purchaser must submit Sightron coupon with original sales receipt, warranty card and UPC sticker by March 31st 2010. Rebate offer cannot be combined with any other discounts or offers.

Wind-Reading Skills for Hunting

On LongRangeHunting.com, you’ll find a good article about wind reading by Shawn Carlock. Shawn Carlock is a veteran law enforcement marksman and the current USPSA national precision rifle champion. Shawn offers good advice on how to estimate wind speeds and directions using a multitude of available indicators — not just your wind gauge: “Use anything at your disposal to accurately estimate the wind’s velocity. I keep and use a Kestrel for reading conditions….The Kestrel is very accurate but will only tell you what the conditions are where you are standing. I practice by looking at grass, brush, trees, dust, wind flags, mirage, rain, fog and anything else that will give me info on velocity and then estimate the speed.”

Shawn also explains how terrain features can cause vertical wind effects. A hunter positioned on a hilltop must account for bullet rise if there is a headwind blowing up the slope. Many shooters consider wind in only one plane — the horizontal. In fact wind has vertical components, both up and down. If you have ever piloted a small aircraft you know how important vertical wind vectors can be. Match shooters will also experience vertical rise when there is a strong tailwind blowing across an up-sloping berm ahead of the target emplacements. Overall, Shawn concludes: “The more time you spend studying the wind and its effect over varying terrain the more successful you will be as a long-range shooter and hunter.”

Smith & Wesson Recalls Walther PPK and PPK/S Pistols

On February 20, 2009, Smith & Wesson issued a RECALL of Walther PPK and PPK/S pistols. This recall applies to all Walther PPK and PPK/S pistols manufactured by Smith & Wesson from March 21, 2002, until February 3, 2009. Smith & Wesson has identified a condition that may exist in certain PPK and PPK/S pistols which may permit a round to be discharged without the trigger being pulled. When the manual safety is disengaged, Smith & Wesson’s Product Engineering Group has determined that the possibility exists in certain firearms that lowering the hammer may cause a chambered round to fire.

CLICK HERE for the Serial Numbers of the pistols subject to this recall.

Remedy and Action to Be Taken
Smith & Wesson advises: “STOP USING YOUR PISTOL AND RETURN IT TO SMITH & WESSON AT ONCE. Any unintended discharge of a firearm has the potential for causing injury, and we ask that you stop using your pistol immediately.

When you return your pistol to Smith & Wesson, we will replace the existing hammer block feature with a new part at no cost to you. Your firearm will be returned as quickly and efficiently as possible. When your pistol is returned, you should note a punch dot which appears at the back of the frame. See the photograph below. This marking is verification that the new hammer block has been installed and that your pistol is safe to handle.”

FREE Shipping Voucher and Instructions
To receive a UPS pre-paid billable stamp and shipping instructions to arrange for the modification of your pistol, CLICK HERE or contact Smith & Wesson directly at 1-800-331-0852.

Have Guns, Will Travel — NCSA Mobile Shooting Club

This story comes to us courtesy of the NRA Blog, which recently featured the innovative program of the North Coast Shooters Association (NCSA). The NCSA has pioneered a “movable match” that utilizes multiple shooting facilities to expand the opportunities for competitive shooters in the Midwest and Ohio region. The NCSA is a mobile shooting club. Instead of owning its own range, the NCSA has a trailer loaded with everything needed to hold a match including homemade spotter discs, spindles, and pasters. The NCSA holds its competitions wherever they find enough interest, rather than trying to draw people to one location. This unique approach attracts first-time shooters and those adverse to traveling long distances, creating a nice turn-out every time.

NCSA Offers Matches at Military Bases
A little over a year and a half ago, NCSA founder Nick Mullet decided there weren’t enough places to shoot east of the Mississippi River. As a result, the North Coast Shooters Association was formed with the mission of opening additional ranges for civilian shooters. Nick contacted military bases normally closed to civilians and got permission to hold matches. The NCSA secured .50 and .223 caliber matches at Fort Knox, Fort McCoy, Fort Drum, Camp Gruber, Camp Perry, and Thunder Valley.

“From our start in mid 2007, we’ve held five .50 caliber matches and two .223 matches in four different locations throughout three states”, Nick stated. The NCSA has grown to 74 paid members and has high hopes for the future. With increased membership comes more frequent competitions over a larger area. Any and all skill levels are welcome to NCSA matches as long as they follow Nick’s two basic rules: 1) No one has the authority to get hurt; and 2) Have a good time.

For more information, visit the North Coast Shooters Association website and NCSA Forum. The NCSA may be planning a match near you.