When shopping for a new riflescope or spotting scope it’s easy to get confused by all the technical terminology. Do you wish you had a better way to compare scopes — beyond just size, weight, and price? Well Swarovski Optik can help. The Swarovski Hunting Blog offers a helpful guide to technical terms used when comparing scope specifications. Here are some important definitions, expressed in layman’s language:
Objective Lens Diameter
The objective lens diameter determines the size of the optical system’s entrance pupil. The bigger the objective lens diameter, the more light the system can capture. However, the size of the objective lens does not determine the size of the field of view.
Exit Pupil
The size of the Exit Pupil is determined by the objective lens diameter and the magnification. If you look at the eyepiece from a distance of around 30 cm (11.8 in), the Exit Pupil appears as a bright disc.
For calculating the Exit Pupil the formula is:
Exit Pupil = objective lens diameter ÷ magnification (expressed in power number).
The larger the Exit Pupil, the more light will reach the eye.
Field of View
The Field of View is the size of the circular section of the area which can be observed when you look through a long-range optical device. In the case of rifle scopes, it is specified at a distance of 100 meters or 100 yards. For example, 42.5 m at 100 m or 127.5″ at 100 yards. As an alternative, the Field of View can also be stated in degrees (e.g. 6.6°).
NOTE: The technically-feasible size for the Field of View is essentially determined by the magnification. The higher the magnification the smaller the Field of View.
Twilight Factor
The Twilight Factor defines the optical system’s performance in poor light. The statement “the greater the twilight factor, the better the suitability for twilight” only applies if the exit pupil is larger than or at least as big as the eye’s pupil. The pupil in the human eye can only open to around 8 mm. As we get older, our eyes become less flexible, which limits our ability to see things in twilight or at night. Therefore [an optic’s] exit pupil cannot always be fully utilized.
For calculating the Twilight Factor the formula is:
Twilight Factor = root of ( magnification x objective lens diameter ).
NOTE: Spotting scopes have extremely high twilight factors because of their high magnification and large objective lens diameter. But [when used at high magnification] their small exit pupil can make them [somewhat difficult] to use in twilight.
The latest 7th Edition of the Firearms Guide is now available as a handy USB Flash Drive, as well as DVD. In addition, you can access the information on the web via an online subscription. (NOTE: the DVD Edition is FREE in combo with a 1-Year Online Database subscription.)
“We listened closely to the market,” says Firearms Guide editor Chris Mijic, “and saw that our online users still want to have a tangible backup copy of Firearms Guide. A lot of them like the DVD Edition which is free with the Online Edition but some of them don’t have a DVD drive in their new computers any more so we created a super-fast USB Flash Drive edition for them.” The Firearms Guide 7th Edition is also published on DVD-Rom for Windows and there is an online subscription service at www.firearmsguide.com.
Choose Multiple Options
USB Flash Drive Edition comes in combo with a 1 Year Online Edition with free updates for only $39.95.
1-Year Online Edition with free updates is only $29.99.
DVD Edition is FREE in combo with a 1-Year Online Edition.
The Firearms Guide 7th Edition represents the world’s largest, fully-searchable firearms, air guns and ammo database, covering 920 manufacturers from 50 countries. Published since 2009, the Firearms Guide covers over 64,000 antique and modern guns, with gun values, photos, and high-resolution gun schematics and blueprints. The Firearms Guide allows up to 14 different search criteria: caliber, year, country, manufacturer, stock, action, price, and more.
The amount of imagery is amazing — there are tens of thousands of photos and over 6300 schematics, which help you work on a firearm or identify key components/parts. Guns and ammo are presented with prices, specifications, features, ballistics, and up to 12 high-rez zoom-able color pictures.
GUN VALUES are provided for dealers and gun collectors. You can access thousands of printable and zoom-able GUN SCHEMATICS (diagrams or exploded views) with parts lists and blueprints for professional gunsmiths.
This shocking photo of destroyed AR-15 bits and pieces was posted on Facebook by William Walter, a firearms instructor. William said this was “The worst AR-15 blow-up I have ever seen. Has anyone else seen one this bad?” It is indeed catastrophic. Seeing the above image, our friend Grant Ubl wrote: “that is most definitely THE most FUBAR’d AR15 that I have ever seen”.
Luckily the shooter sustained only minor injuries — nothing worse than a broken finger tip. But his AR-15 is certainly toast. The lower was polymer. Note the past tense. According to Walter: “It was a polymer lower and polymer magazine. Pieces of both were distributed up to 25 feet from the bench he was firing from.”
The cause of the Kaboom is somewhat mysterious. The Kaboom occurred on the 4th round fired — the first three went OK, and there is NO evidence of a squib load (i.e. no bulge in barrel). This was definitely NOT a .300 BLK round in a .223 Rem Chamber. William Walter suspects that pistol powder may be involved, but that has not been confirmed.
First thing I suspected was bore obstruction, but there wasn’t any sign of it. The case head literally atomized…you can see the brass residue on the parts. The bolt was split in two also. This was number four fired during load testing. The previous three were fine…no high pressure signs on the primer. — William Walter
One Facebook poster noted: “We had one similar here in PA about 14 years ago. The guy used Winchester 231 instead of Winchester 748 and ended up with a pile of parts very similar looking. The rifle went Kaboom on his first sighter in offhand and no one was injured surprisingly. The carrier looked like someone cut it down the middle with a torch very similarly to this picture. It also cut the bottom of the carrier and all three pieces look like a peeled banana.”
Walter stated that here: “[The shooter] had fired four rounds of the same load. He was shooting Win 748…24 grains with a 77 Sierra. I will reserve my theory until after we discuss as to not steer the conversation.
On reading that, Dennis Santiago posted: “Did you mean WW 748? That’s on the fast side powder for a .223 meant for lighter bullets. 24 grains with a long bullet like a Sierra 77 would be way too much.”
Walter noted that there was a possibility of some pistol powder getting into the catridge that detonated: “[The shooter] said he does load pistol and this was first time loading rifle. He said he used his 650 powder measure, but also a funnel and trickler.” Considering that, one poster suggested that maybe pistol powder was still left in the bottom of the powder measure.
It will be interesting to determine what exactly happened here. The remaining rounds from the same loading session will be pulled down and analyzed. A discussion of this incident appears on the Precision Shooting Journal Facebook Page.
Question to our readers: What do you think was the probable cause of this catastrophic Kaboom?
H.R. 788 will help States build and maintain shooting ranges with Federal funding assistance.
Federal Legislation has been introduced that will help build and maintain shooting ranges. H.R. 788, the Target and Marksmanship Training Support Act of 2017, was introduced in Congress by Rep. Duncan Hunter (R-CA) and a bipartisan group of 23 co-sponsors. The provisions of H.R. 788 will help States fund public shooting ranges with Federal Firearms Excise tax revenues.
“This legislation [H.R. 788] would provide state fish and game agencies more flexibility to use Pittman Robertson excise taxes dollars raised from the sale of firearms and ammunition to enhance existing public shooting ranges and to build new ones to meet the growing need for additional places for target shooters to participate in their sport,” said Lawrence G. Keane, NSSF Senior V.P. and General Counsel. “Public shooting ranges provide hunters a place to sight-in rifles and shotguns before hunting seasons, for people to take firearm safety and hunter education courses, and for recreational target shooters to enjoy their sport.”
Since 1937 almost $11 billion has been raised for wildlife conservation through the Pittman-Robertson excise tax on the sale of firearms and ammunition. States are permitted to use some of those funds for hunter education courses and for public shooting ranges under a restrictive formula that has largely discouraged state agencies from building and enhancing public shooting ranges. H.R. 788 will help states use Pittman Robertson revenues by increasing the limit on Federal funding of shooting ranges from 75 to 90 percent. This means states could begin work on range facilities with 10 percent State-supplied funding, instead of the current 25 percent. It would also allow Federal Excise funds to be made available and accrue for five years for land acquisition or range construction.
In addition, the legislation would limit frivolous lawsuits arising from the use of Federal land for target practice and encourage Federal agencies to cooperate with state and local authorities for maintenance of ranges on federal lands.
Story by NRAHuntersRights.org and NRAblog.com
Shown above is the Belfast Wildlife Area rifle range in Kindards, SC. Belfast was the first public, unmanned shooting range opened and paid for completely with funds raised by NRA Grants and the Wildlife and Sportfish Restoration Program … an act made possible through Pittman-Robertson grants. Several other state Natural Resource Departments have followed suit.
Legislative History: The Target and Marksmanship Training Support Act was previously introduced as H.R. 2406, the SHARE Act (Title II), and the Bipartisan Sportsmen’s Act in the last Congress, as well as a stand-alone bill H.R. 2463 in the 113th Congress.
Photo Credit: Top photo shows Mainville Sportsman Club (PA) and Union Co. Sportmen’s Club (PA), both sites of IBS Matches.
If you’ve never visited the NRA Whittington Center outside Raton, New Mexico, it is well worth a visit. This new HD video shows the features of this unique facility where marksmen can shoot from 10 yards to two miles. Drone video footage gives you a “birds eye view” of the scenery and the ranges.
This is an excellent video. Well worth watching, with impressive aerial photography.
The Whittington Center hosts many major matches each year. Along with the training and range facilities, the Whittington Center has comfortable, modern cabins and RV camping zones for extended stays. Founded in 1973, the Center offers ranges for every kind of shooting discipline, along with a shotgun center, firearms museum, specialized firearms training, guided and unguided hunts, plus an adventure camp for younger shooters.
Forum member Bill Goad’s 6XC II Hunter Rests in a Whitetail Rack taken this past year.
One of the most popular items in our Shooters’ Forum is the ongoing “Pride and Joy” thread. Since 2009, Forum members have posted photos and descriptions of their most prized rifles. Here are some of the most recent “Pride and Joy” rifles showcased in our Forum. Do you have a gun you’d like to see featured there? Just Register for the Forum and you can add your favorite gun to the list.
TT Freestyle’s Husband and Wife Borden Benchrest Rifles
Here’s a pair of “His and Hers” rigs delivered by Santa in December. Forum member TT Freestyle reports: “After our rookie year in Short Range Benchrest with good used equipment, my wife and I decided we liked it enough to get two new Bordens for Christmas!”
FalconPilot’s Fabulous F-Classer in Shurley Claro Walnut Stock
This beauty belongs to Forum member FalconPilot. He tells us that his “Lastest F-Classer features a Shurley Brothers SOD stock in beautiful Claro Walnut.” Components include Bat M action, Bix-N-Andy trigger, and Nightforce Comp scope. FalconPilot has several barrels for this Open-Class rig, including tubes chambered for .284 Win and 6mm Dasher.
Eric’s Blacktical .308 Win for Precision Rifle Series
Forum member Eric32 spent months building out this rifle, “getting it to work just right for PRS”. Designed for practical/tactical matches, this rugged rig features a blue-printed Rem 700 action (with 1.5-lb 40X trigger) in an XLR Element chassis. On the end of the .308 Bartlein 5R barrel is a JP brake. Other components include: PiG skins barricade grips, Atlas Bipod, and GGG bungee sling. On top is a SWFA HD 5-20x50mm optic with Vortex scope level and custom throw-lever.
Forum member Willow reports: “Here is my new F-Open gun. It features a hydro-dipped LowBoy stock and LH Barnard Model P action with ‘V’ bedding block. The barrel is a straight profile 32″, 1:8.5″ twist Bartlein 5R, chambered in 280AI by Matt Paroz”. On top is a Vortex 10-60x52mm Golden Eagle in a Spuhr 3001 mount. Willow says his lightning bolt rig is a shooter: “After 42 rounds through the barrel, I’m liking what I am seeing so far”. Check out that trick aluminum base for his rear Edgewood bag.
Stinnett’s 6.4×47 Lapua Tactical Rig
Forum member Stinnett tells us: “This is my third 6.5×47 Lapua rifle — the 6.5×47 is the best cartridge ever! I’m not a huge fan of muzzle brakes. I look at them as tools — use the correct tool for the job. The ’47 doesn’t need a brake. .308 Winchester and up need muzzle brakes. For this rifle, I’m going to start out with 123gr Scenars and Reloder 15. I also like to shoot the 123gr SMKs and Varget. The SMKs are much less seating-depth sensitive. Very easy to find a load! Also gonna try the Berger 130 Hybrids and H4350.”
Components: McMillan A5 adjustable stock in GAP Camo, Stiller TAC 30 A/W action, Jewell HVR trigger, Badger bottom metal and DBM, Atlas Bipod, Nightforce NXS F1 3.5-15×50 with MLR 2.0 reticle. Metal has been Cerakoted graphite black.
6mm BRX Benchgun with Home-Made Cherry/Redheart Stock
You have to give credit to a guy who crafts his own custom wood stock. This 6mm BRX benchgun features a custom-built laminated stock featuring Cherry wood with vivid Redheart pieces on the sides and Redwood Burl on the buttplate. The front of the stock is 4″ wide. The action is a Benchrest Borden RBLP Right Eject unit, with custom titanium scope rings on top. Owner Erick C. is proud of this stock, saying it is “the best one I’ve built so far”. We agree it’s a beauty.
Many of our Forum members shoot an “improved” 6mmBR cartridge. This might be a 30°-shoulder 6mm BRX, or a 40°-shoulder 6mm Dasher, or the 6mm BRDX, which is very similar to the Dasher, but with a slightly longer neck. This Editor shoots a 6mm BRDX and has found it very accurate, and maybe a bit easier to fire-form than a standard Dasher. Speaking of fire-forming, in our Shooters’ Forum, we often see questions about fire-forming BRX/Dasher brass. For those who need a large number of BRX or Dasher cases, one option to consider is using pistol powder in a dedicated fire-forming barrel. Here’s an explanation of how this process can work.
Forum member Skeeter has a 6mm Dasher falling block varmint rifle. The Dasher case is based on the 6mmBR Norma cartridge with the shoulder blown forward about 0.100″ and out to 40°. This gives the Dasher roughly 3.5 grains added capacity compared to the standard 6BR.
A few seasons back, Skeeter needed to form 300 cases for varmint holiday. Skeeter decided to fire-form his brass without bullets. This method avoids barrel wear and saves on components. There are various ways to do this, but Skeeter chose a method using pistol/shotgun powder, some tissue to hold the powder in place, Cream of Wheat filled to within an 1/8″ of top of the neck, and a “plug” of tissue paper to hold it all in place. Shown below are cases filled with a pistol/shotgun powder charge topped with Cream of Wheat and then a tissue paper plug.
To ensure the case headspaced firmly in his Dasher chamber, Skeeter created a “false shoulder” where the new neck-shoulder junction would be after fire-forming. After chamfering his case mouths, Skeeter necked up all his cases with a 0.257″ mandrel (one caliber oversized). Then he used a bushing neck-sizing die to bring the top half of the neck back down to 0.267″ to fit his 0.269″ chamber. The photo below shows how the false shoulder is created.
After creating the false shoulder, Skeeter chambered the cases in his rifle to ensure he could close the bolt and that he had a good “crush fit” on the false shoulder, ensuring proper headspace. All went well.
The next step was determining the optimal load of pistol powder. Among a variety of powders available, Skeeter chose Hodgdon Titewad as it is relatively inexpensive and burns clean. The goal was to find just the right amount of Titewad that would blow the shoulder forward sufficiently. Skeeter wanted to minimize the amount of powder used and work at a pressure that was safe for his falling block action.
Working incrementally, Skeeter started at 5.0 grains of Titewad, working up in 0.5 grain increments. As you can see, the 5.0 grain charge blew the shoulder forward, but left it a hemispherical shape. At about 7.0 grains of Titewad, the edge of the shoulder and case body was shaping up. Skeeter decided that 8.5 grains of Titewad was the “sweet spot”. He tried higher charges, but the shoulder didn’t really form up any better. It will take another firing or two, with a normal match load of rifle powder and a bullet seated, to really sharpen up the shoulders. Be sure to click on the “View Larger Image” link to get a good view of the cases.
The process proved to be a success. Skeeter now has hundreds of fire-formed Dasher cases and he hasn’t had to put one bullet through his nice, new match-grade barrel. The “bulletless” Cream of Wheat method allowed him to fire-form in a tight-necked barrel without neck-turning the brass first. The only step now remaining is to turn the newly Dasher-length necks down about .0025″ to fit his 0.269″ chamber. (To have no-turn necks he would need an 0.271″ or 0.272″ chamber).
Skeeter didn’t lose a single case: “As for the fire-forming loads, I had zero split cases and no signs of pressure in 325 cases fire-formed. Nor did I have any misfires or any that disbursed COW into the action of the firearm. So the COW method really worked out great for me and saved me a lot of money in powder and bullets.”
Skeeter did have a fire-forming barrel, but it was reamed with a .269 chamber like his 10-twist Krieger “good” barrel. If he fire-formed with bullets, he would have to turn all 300 necks to .267″ BEFORE fire-forming so that loaded rounds would fit in the chamber. Judging just how far to turn is problematic. There’s no need to turn the lower part of the neck that will eventually become shoulder–but how far down the neck to turn is the issue. By fire-forming without bullets now he only has to turn about half the original neck length, and he knows exactly how far to go.
2021 Update: This product has been discontinued, but may still be available at some retailers. But it cannot be purchased on Amazon.com.
Wouldn’t it be cool if your gun case could do double-duty as a shooting mat? That would be smart — you’d have one less item to carry to the range. Well such a thing does exist. Uncle Mike’s Long Range Tactical Bag protects your rifle during transport, then quickly and easily converts to a 78″ shooting mat. Measuring 50″ in length, with a 15″-tall main compartment, this bag is big enough to handle most tactical and F-TR rifles with optics and Harris-type bipods attached. A 30″ flip-out forward section includes a front load strap that allows shooters to pre-load the bipod legs while shooting prone.
The Long Range Shooting bag has four self-adjusting magazine pockets, which will hold magazine sizes from .223/5.56mm to .308/7.62mm. Conveniently, this new 50″-long soft case will fit inside the popular Pelican model 1750 hard case (for those situations where you need greater protection).
Fits Long-Range and Tactical rifles up to 49″ in length
Fold out front section has bi-pod front load strap
The 45th Annual Safari Club International (SCI) Convention is underway now at the Mandalay Bay Resort and Casino in Las Vegas, Nevada. The big event opened February 1st, and concludes Saturday the 4th. Over 20,000 hunters and sportsmen are expected to attend this year.
$10 Million in Auction Items This Year
The SCI show is famed for its fund-raising auctions. At this year’s Convention, over $10 million worth of exotic firearms, once-in-a-lifetime hunts, and fine collectibles will be auctioned. Net proceeds from the auctions are used by SCI to promote conservation and game management efforts worldwide. Here’s a past auction item, a Krieghoff Double Rifle valued at $84,000. This ‘Legends of the Hunt’ double rifle, chambered in .470 Nitro Express, is custom engraved by master engravers Michael Oke and Andreas Scholz. The stock is exhibition-grade Turkish walnut with ebony pistol grip and fore-end tip. There are gold barrel bands and gold accents on the express sight blades and double triggers.
Over 1000 Exhibitors from 33 Countries
This is a huge event, with over 1000 exhibitors from 33 countries and six continents. Notably, hundreds of top guides and outfitter services are showcased in the Outfitters Hall. The SCI convention also features many firearms manufacturers and custom gun builders. In the Gun Maker’s village prestigious European gun makers and engravers display their work.
The SCI convention boasts “the largest display of wildlife art at one venue anywhere in the world” according to Ammoland.com. The work of 55 artists and 110 taxidermists will be on display.
Hunt of a Lifetime — What Would You Hunt and Where?
A couple seasons back, Sierra Bullets asked its staffers about their dream hunting destinations. The Sierra techs, all avid hunters, were polled about their favorite hunting venues. Here are their answers to the question: “If you could hunt anything, anywhere in the world, where would you go and what would you hunt?”
Africa topped the list of “dream hunting locations” by a landslide. Canada and Alaska were both picked twice, with other destinations each favored by one staffer:
Africa 6 votes (Kudu, Eland, Cape Buffalo, Leopard, Lion, Plains Game)
Canada 2 votes (Moose, Black Bear)
Alaska 2 votes (Dall Sheep)
Wyoming 1 vote (Antelope)
US Rocky Mountains 1 vote (Elk)
Argentina 1 votes (Doves)
Australia 1 vote (Non-specific)
Carroll Pilant (Ballistics Technician): “Back to Africa for kudu and eland.”
Rich Machholz (Ballistic Technician): “African Cape Buffalo with my longtime friend Lloyd in Zimbabwee.”
Tommy Todd (Chief Ballistician): “Free Range African plains game”
Applied Ballistics has created a series of YouTube videos about precision long range shooting. Featuring ace long-range shooter and professional ballistician Bryan Litz, these videos will address various topics of interest to long-range marksmen. In this video, the first in the series, Bryan Litz answers the question, “Just What Is Long Range Shooting?” Bryan discusses how we define “long range” and the key factors shooters need to consider.
Applied Ballistics Video — What Is Long Range Shooting?
Bryan states: “I don’t think there is a clear definition of where Long Range starts.” But he offers this practical guideline: “The way I think of it, any time you’re making major adjustments to your zero in order to hit a target, due to gravity drop and wind deflection, THEN you’re getting into ‘Long Range’. For example, if you are zeroed at 100 yards and need to shoot to 600 yards, you have many feet of elevation [drop] to account for, and to me, that’s where it becomes Long Range.”
Extended Long Range and the Transonic Zone
Bryan adds a second concept, namely “Extended Long Range”. Litz says that: “Extended Long Range starts whenever the bullet slows to its transonic range. As the bullet slows down to approach Mach 1, it starts to encounter transonic effects, which are more complex and difficult to account for, compared to the supersonic range where the bullet is relatively well-behaved.” Bryan notes that bullets start to encounter transonic effects at about 1340 fps, quite a bit faster than the speed of sound, which is about 1116 fps at sea level in normal conditions (59° F).
When shopping for a new riflescope or spotting scope it’s easy to get confused by all the technical terminology. Do you wish you had a better way to compare scopes — beyond just size, weight, and price? Well Swarovski Optik can help. The Swarovski Hunting Blog offers a helpful guide to technical terms used when comparing scope specifications. Here are some important definitions, expressed in layman’s language:
