As part of its online Load Data Center, Nosler offers very complete load data for the popular 6.5 Creedmoor cartridge. This medium-sized cartridge has become one of the most popular chamberings for tactical and PRS shooters. The 6.5 Creedmoor combines excellent accuracy, good mag-feeding, good barrel life, moderate recoil, and reasonable component cost. That’s why this cartridge has caught on quickly. GET ALL 6.5 Creedmoor Load Data.
How does barrel length affect 6.5 Creedmoor Muzzle Velocity? CLICK HERE for RifleShooter.com barrel cut-down velocity test.
According to the Sierra Load Manual: “Developed in 2007 by Dennis DeMille and Dave Emary, the 6.5 Creedmoor is a shortened and improved 30 TC cartridge case that was inspired by the .308 Winchester design. This short action design was created to maximize case capacity and a wide range of loading lengths, while still fitting in standard short action magazines. With the correct twist barrel, the versatile 6.5 Creedmoor can take advantage of the wide range of bullet weights available in 6.5 mm (i.e. .264 caliber). Reloaders should keep in mind that the 6.5 Creedmoor works best with medium to medium-slow powders such as H4350, Varget, Win 760, and RE-17.”
Click Image to Load PDF File for Listed Bullet Weights
Well folks, it’s July 1st already — the means we’re moving into “peak heat” summer conditions. It’s vitally important to keep your ammo at “normal” temps during the hot summer months. Even if you use “temp-insensitive” powders, studies suggest that pressures can still rise dramatically when the entire cartridge gets hot, possibly because of primer heating. It’s smart to keep your loaded ammo in an insulated storage unit, possibly with a Blue Ice Cool Pak if you expect it to get quite hot. Don’t leave your ammo in the car or truck — temps can exceed 140° in a vehicle parked in the sun.
To learn more about how ambient temperature (and primer choice) affect pressures (and hence velocities) you should read the article Pressure Factors: How Temperature, Powder, and Primer Affect Pressure by Denton Bramwell. In that article, the author uses a pressure trace instrument to analyze how temperature affects ammo performance. Bramwell’s tests yielded some fascinating results.
For example, barrel temperature was a key factor: “Both barrel temperature and powder temperature are important variables, and they are not the same variable. If you fail to take barrel temperature into account while doing pressure testing, your test results will be very significantly affected. The effect of barrel temperature is around 204 PSI per F° for the Varget load. If you’re not controlling barrel temperature, you about as well might not bother controlling powder temperature, either. In the cases investigated, barrel temperature is a much stronger variable than powder temperature.”
Powder Heat Sensitivity Comparison Test
Cal Zant of the Precision Rifle Blog has published a fascinating temp-stability comparison test of four powders: Hodgdon H4350, Hodgdon Varget, IMR 4451, and IMR 4166. The first two are Hodgdon Extreme powders, while the latter two are part of IMR’s new Enduron line of propellants.
The testers measured the velocity of the powders over a wide temperature range, from 25° F to 140° F. Hodgdon H4350 proved to be the most temp stable of the four powders tested.
Rimfire Benchrest can be fun and rewarding. It can also be frustrating because sourcing superior lots of ammo is a never-ending challenge. Still we like rimfire benchrest because you don’t need to load at the range. Plus rimfire barrels last a very long time (our friend Joe Friedrich set an ARA Benchrest record with a 100,000+ round-count barrel). Here’s a great video from the National Rimfire Benchrest Association of Ireland (NRBAI). Production quality is excellent! We highly recommend you watch this video, which does a great job illustrating both the fun and challenge of rimfire benchrest competition.
If you’ve never seen 50m Rimfire Benchrest competition, this video is well worth watching:
“If you need to get your mind away from everything… then look down a scope, concentrate, and be disciplined.”
“Comradery is one of our organization’s key traits… there are no barriers of gender, age or mobility. Just a very diverse, bunch of good people enjoying a sport together.”
“The skill, in brief, is having the ability to hit the equivalent of the top of a pinhead at 50 meters, in all conditions with a .22 round. Not easy, especially when you have to do it 50 times to get a maximum score of 500 [points], 250 per sheet.”
Credit Boyd Allen for finding this NRBAI Benchrest Video, released on 6/28/17.
Report by Corbin Shell
Not long ago, I learned of the King of 2 Miles (KO2M) shoot held in Raton, NM and was fortunate enough to get an entry slot. I will be shooting with David Tubb, multi-time High Power and Long Range National Champion, on a team we call the “Second Amendment Cowboys”. Given such short notice, I scrambled to find the necessary components to build a suitable rifle for the event. I turned to longtime friend and owner of X-Treme Shooting Products (XTSP), Tom Myers, to see if he might have a suitable action. XTSP is known for its premium titanium rifle receivers, however XTSP also manufactures stainless actions. As luck would have it, Tom was completing a small run of .338 Lapua Magnum-sized stainless steel single-shot actions. Other components were sourced as quickly as possible and the building began in earnest.
Before acquiring the first component for this build I already knew who was going to perform the work, Doyle Anglin at Dixie Guns, inc.. Doyle’s attention to detail and rifle building knowledge is second to none! I came to Doyle with the idea of building a rifle to shoot in the King of 2 Miles match and his ears perked up. Once all the components were in hand Doyle began construction. Doyle was given free liberty to build whatever he felt best for the job given the time constraints and components that were readily available on such short notice. I cannot thank Doyle Anglin enough for the stellar job he did!
KO2M .338 Lapua Magnum Improved — Rifle Components
— Custom laminated stock Doyle Anglin designed and created from scratch
— 10″-long aluminum barrel block designed and made by Doyle Anglin
— XTSP (X-Treme Shooting Products) PH420 stainless single shot receiver 1.450” diameter. PVD-coated receiver body. FNC-coated one piece bolt.
— XTSP +35 MOA and +60 MOA tapered Picatinny rails, PH420 stainless, PVD-coated
— XTSP two-stage trigger with safety
— Krieger 1:9.3″-twist barrel. 1.450” for 6.5” tapering to 1.100” at the muzzle. 33.5″ finished length
— Piercision Rifles 3/4×24 slab-sided, 5-port muzzle brake
— BAT stainless trigger guard
— Masterclass cheek piece with extended rods
— Masterclass butt plate hardware
— Duplin Bipod
— Spuhr +20.6 MOA one piece scope mount
— Ivey +175 MOA adjustable scope mount
— Sightron SIII 6-24x50mm MOA-value scope (100 MOA of total travel)
— Geier & Bluhm 10 minute precision bubble level mounted to barrel block via extension rod
— Manson .338 Lapua Magnum Improved 30-degree reamer, .375” neck diameter
Load Information
— Sierra 300 grain MatchKing, meplats trimmed and pointed, seated .010″ into lands*
— Hodgdon Retumbo Powder, 101 grains
— Peterson .338 Lapua Magnum brass
— Federal 215 primers
— Jim Carstenson custom reloading dies: inline seater, full-length bushing, neck bushing and threaded micrometer seating die
This load has achieved 3050fps with low single-digit SDs
Given the 12-pound barrel weight, Doyle strongly suggested a barrel block to offer additional support and increase rigidity. Doyle created a split ten-inch aluminum barrel block and mating steel plate that is inletted into the forend of the custom laminated stock. The 1:9.3″-twist Krieger barrel is epoxied into the barrel block as well as being held in place by the ten socket head cap screws. Two hardened and ground pins locate and index the barrel block onto the steel mating plate. The steel mating plate acts as the recoil lug which mates up to the cut on the reward section of the barrel block. The Krieger barrel is chambered with a 30-degree Lapua Magnum Improved reamer and throated accordingly, yielding a loaded round of approximately 4.000 inches.
The barrel is capped with a very effective Piercision Rifles 3/4×24 slab-sided, five port muzzle brake. The size proportions of the muzzle brake work well with the 1.100” muzzle diameter, however it will work on barrels up to 1.450″ in diameter.
Doyle Anglin worked his creative magic and constructed the multi-color laminated stock from a blank. The five inch fore-end allows the rifle to be utilized in a dual role — either benchrest or prone with bipod. The cheek piece hardware is from Master Class Stocks and is adjustable for cast on/off with preset elevation settings via half-moon shaped clips. The two-way adjustable butt plate hardware also comes from Alex Sitman at Master Class Stocks. The multi-colored laminate stock is clear-coated with special marine UV inhibitor paint. The glass smooth finish makes the wood appear wet and is extremely smooth to the touch.
Lots of Elevation on Tap with Angled Rails, Spuhr and Ivey Mounts
Topping off the rifle is either a +35 or +60 MOA X-Treme Shooting Products Picatinny scope rail. The receiver and scope rails are pinned for accurate repeatability when interchanging. Five 8×40 socket head cap screws firmly hold the scope rail in place. A SPUHR +20.6 MOA tapered, one-piece scope mount securely grasps the Sightron SIII 6-24x50mm MOA scope. I cannot say enough good things about the quality of the SPUHR scope mount! This is the only fixed scope mount that I will use going forward and a special thanks goes out to Ulf at SPUHR! The 35 MOA rail and 20.6 MOA SPUHR mount setup allows full utilization of the Sightron’s 100 MOA of internal travel. The second scope setup is comprised of an Ivey +175 MOA adjustable scope base and Sightron SIII 6-24x50mm optic.
Scope in SPUHR mount shown below:
Scope in IVEY Mount with barrel block-mounted precision bubble level:
When shooting extended long range (ELR) it is important that the scope’s crosshairs remains level. Should the crosshairs be canted it will induce impact shift which increases with the angle of cant and distance. The decision was made not to use any of the lesser quality/precision bubble levels that currently flood the market. These levels have poor resolution usually between one and two and a half (1-2.5) degrees. It must be noted that not all levels are created equal. The fine folks at Geier & Bluhm offered up a solution with a precision glass vial horizontal level with an accuracy of ten minutes. As a refresher, one degree is comprised of 60 minutes of angle. The level setup we chose for this rifle is, at minimum, six times more accurate than the best scope or picatinny level on the market. The 10 MOA bubble level sensitivity is just about perfect and does not create a situation of having to “chase” the bubble left and right when in position.
A portable 150 MOA tall target was created to test both scope tracking and crosshair alignment. When testing at the local 100-yard range I got a lot of strange looks and a few inquiries as to why in the world was I shooting thirteen FEET above the aiming bullseye.
As the F-TR shooters have learned, it is very important that the rifle travel freely and repeatable under recoil. I turned to Ray Gross who custom made a rubber and Cordura shooting mat which the bipod rides on. This mat is of the same material and construction that most of the F-TR team is utilizing. The rubber durometer is correct so the rifle does not bounce or hop when fired. The bipod skis slide very easy on the Cordura-topped mat. A big thanks goes to Ray Gross for assisting with the mat setup. In addition, high molecular weight polyethylene (HMWPE) tape was applied to the butt stock of the rifle. The HMWPE tape allows for extremely low friction between the butt stock and rear sand bag. This configuration tracks very well and slides rearward like it is on rails.
As load development progressed I tested three different brands of projectiles. A ladder test was performed at 300 yards to determine where the node was with my barrel and powder combination. The rifle liked between 99-101 grains of Hodgdon Retumbo. I then proceeded to shooting ten shot groups at 1000 yards. In this rifle the Sierra 300gr Matchking was hands down the winner for smallest groups and the best elevation at 1000 yards. The load settled on is 101 grains of Retumbo and 300 grain Sierra Matchking. 500 Sierra bullets were measured base to ogive and the spread over the entire 500pc measured .003” with 490pc varying by .001”. Keep up the good work Sierra Bullets! A special thank you goes to John Whidden for generously allowing me to come to his shop and repoint the Sierra .338 projectiles and allowing me to test at his 1000 yard range.
Preparation for the King of 2 Miles match has been a great learning experience and a lot of fun! Next year’s rifle design is already in the works and should be an over the top build. Stay tuned to AccurateShooter.com for further details!
* The Sierra 300gr MatchKings were meplat-trimmed and pointed using the original pointing system made by Ferris Pendell for Jim Hardy. A big thank you goes out to John Whidden for allowing me to come to his shop and use the original bullet pointing system.
Here’s a smart product for folks who load and store large quantities of ammunition. With these white cardboard ammo boxes from Repackbox.com, you can store pistol, rifle, and shotshell ammo very inexpensively. A set of 30 boxes costs $13.95 ($0.47/box), while a 100-Box Bundle costs just $22.95. That works out to just $0.23 (twenty-three cents) per box — very cheap!
All boxes are Made in the USA of .024 thick, acid free, virgin card stock. The boxes are printed with Cartridge Type (Caliber), number of rounds enclosed, and an outlined box where a printed label can be placed. Included with each set are Blank Avery 5167 Labels which can be printed with load/bullet data or other info. The box kits even come with white gloves to keep your ammo grease-free. Order these ammo repack box kits from Repackbox.com.
There are many advantages to these cardboard boxes. They are inexpensive and they store ammo very efficiently, not using much space. You can arrange them in any orientation (unlike some plastic ammo carriers). We like these boxes for varmint safaris and other adventures when we’re transporting many hundreds of rounds of ammo. They are also a smart choice for bulk shotshell ammo, as they are much less expensive than plastic shotshell cases. For pistol shooting we still like see-through, plastic flip-top boxes at the range, but these white cardboard boxes are great for storing large quantities of pistol ammo produced on progressive presses. NOTE: These boxes do NOT have individual dividers between the cartridges. And no, the boxes are NOT waterproof — you’ll want to keep them in an ammo can on rainy days.
30-Box and 100-Box Kits are available for all these Pistol and Rifle Cartridge Types:
PISTOL Cartridges
.380 ACP
.38 SPL/.357 Magnum
9mm Luger
.40 S&W
10mm
.44 Magnum
.45 ACP
.45 Long Colt
RIFLE Cartridges
.223 Rem/5.56×45
.30 Carbine
30-30 Winchester
.303 Brit
7.62×39
.308 Win/7.62×51
7.62x54R
.30-06 Springfield
In addition, there are boxes for 12 gauge shotgun ammunition.
At the request of our readers, we provide select “Deals of the Week”. Every Monday morning we offer our Best Bargain selections. Here are some of the best deals on firearms, hardware, reloading components, and shooting accessories. Be aware that sale prices are subject to change, and once clearance inventory is sold, it’s gone for good. You snooze you lose.
1. CDNN Sports — Ruger 17 HMR American Compact, $249.99
With ballistics far superior to a .22 LR, the 17 HMR is ideal for prairie dogs and small varmints out to 180 yards or so. Now you can get a reliable, name brand 17 HMR rifle for a very attractive price. That’s right, CDNN Sports is selling the 17 HMR Ruger American Rimfire Compact, with 18″ barrel, for just $249.99. That includes two (2) comb units and a FREE padded carry sling. FFL required.
2. Monmouth Reloading — Nosler RDF Bullets, $28-$29 per 100
Nosler’s line of RDF (Reduced Drag Factor) bullets have high BCs for their weight. Precision shooters are reporting outstanding accuracy. Given their high performance and consistency, RDF bullets represent a superior value. At Monmouth Reloading you can get Nosler RDFs for under $29 per 100 for popular 6mm, 6.5 mm, and .30-Cal sizes. That’s up to $20 less per box than some premium brands.
3. Grafs.com — Hornady Auto Charge, $179.99 + Free Range Bag
Here’s an excellent promo from our friends at Grafs.com. Hornady’s versatile Lock-N-Load Auto Charge™ Powder Scale and Dispenser is on sale for $179.99. And now for a limited time you get a FREE deluxe range bag ($43.99 value) with the purchase of the Hornady Scale/Dispenser. This is a good unit with a nice keypad. NOTE: You can also get the FREE Range Bag when you buy the Hornady Case Prep Center at Grafs.com for $419.99. That’s pretty pricey — getting Scale/Dispenser with the Range Bag is the better deal.
4. Natchez — Special 5 Reloading Press Kit, $199.99
Looking for a great holiday gift for a family member getting started in metallic cartridge reloading? This RCBS Kit has everything a new reloader needs: single-stage press, powder measure, scale, powder trickler, priming tool, cartridge tray, “rocket” chamfer tool, case lube and more. This is an excellent entry-level reloading kit, on sale for just $199.99 at Natchez Shooters Supplies. We like the relatively compact Special 5 press for most reloading duties. Eventually you may want to add an additional, large heavy press, but this will get the job done. For the combined package, with all the tools one needs to hand-load quality ammo — this is a stunningly good deal at $199.99.
This Master Tumbler Kit contains everything you need to tumble rifle or pistol brass. Now on sale for $56.07 with free Prime shipping, this Kit contains: Vibratory Tumbler, Rotary Media Separator, Plastic Bucket, 3 lbs. Cleaning Media, and 4 oz. Brass Polish. NOTE: We considered this an excellent deal when it was priced at $67.99. At $56.07 it is a total steal — you could easily pay that much for a decent vibratory tumbler alone.
Check out the Harbor Freight Welding Cart, item #65939. This cart is ON SALE right now for just $54.99. With a few bungee cords (and some creativity), the cart can be adapted pretty easily to hauling your gun gear. If you want to enhance the basic cart, it’s easy to add plastic side-panels on the bottom unit, and fit a barrel-holding system on the cross-tube.Overall size is 29-1/2″ L x 20″ W x 49″ H, and width between side rails is 18″. The wheels (with tires) are 20 3/4″ in diameter for smooth rolling. Consider that, if you made your own cart from scratch you could easily pay $30.00 or more just for the large-diameter wheels and axle. Do note — this cart has air-filled tires. Be sure to inflate before you go to the Range!
7. Amazon — Neiko Digital Calipers, $16.79
Even if you have a good set of calipers, you may want to get one of these Neiko 01407A Digital Calipers. The #1 best-selling digital caliper on Amazon.com, this Neiko tool features a large LCD Screen and measures up to 6.0 inches. With 2850+ customer reviews, this product has earned an overall rating of 4.4 out of 5 stars. It’s hard to go wrong for $16.79, even if you just use these as a spare set for measuring group sizes and case trim lengths.
8. Lyman — $25.00 Off Top-Selling Products
You can now get $25.00 Off five of Lyman’s top-selling products: BoreCam, Case Prep Xpress, Gen6 Powder Dispenser, Cyclone Rotary Tumbler, and AutoAdvance Target. With Lyman’s Summer Mail-In Rebate Program, you can earn a $25 rebate per select item bought from any Lyman dealer, online or direct from the Lyman website. Items must be purchased between June 9 and August 31, 2017 to qualify. CLICK HERE for the Rebate Redemption Form.
9. Amazon — Leight MAX NRR33 Earplugs, $7.45 for 50 Pairs.
These Howard Leight NRR33 Max plugs are your Editor’s favorite foam earplugs. They seal out noise better than any others I’ve tried. Between shooting, motorcycling and mowing lawns, I probably have Max plugs in my ears 2-3 days a week. This is a very good price for a bulk pack of 50 pairs (100 plugs). And if you act soon, you can get free shipping to boot.
Some major players in the shooting world — Lapua and Berger Bullets, have joined forces under the Nammo AS umbrella. And now, along with Vihtavuori and SK, these businesses will be operated together as Capstone Precision Group, LLC. And Capstone will soon have a new facility in Missouri. A new 30,000-square-foot logistics center has been leased in Pettis County, outside Sedalia. From here, products will be sent to dealers and wholesalers throughout the USA. Capstone Precision Group will invest almost $1 million to launch the new facility.
Missouri’s Governor welcomed Capstone: “Capstone Precision Group’s decision to grow its business in Missouri is great news for families in rural Pettis County. This new distribution center means new quality jobs for hard working Missourians,” said Gov. Eric Greitens. “We’re grateful to Capstone Precision Group for recognizing that Missouri is open for business and our people are ready to work.” LINK: Missouri Department of Economic Development.
NEW Logistics Center for Capstone Precision Group
Nammo AS, an international aerospace and defense company headquartered in Norway, announced that the newly-formed Capstone Precision Group LLC will launch its U.S. logistics center in Pettis County, outside Sedalia. This facility will be the U.S. logistics center for Capstone Precision Group’s four commercial ammunition brands — Lapua, Berger, VihtaVuori, and SK. Additionally, ammunition, components, and smokeless powder will be imported from Finland and Germany and distributed in the U.S. and also exported, while projectiles from the company’s Mesa, Arizona, location will be shipped to Missouri for packaging and distribution.
Are you a wildcatter? We know many of our readers like to invent new cartridge types. If that applies to you, here’s a great resource…
Fred Zeglin has released a Kindle eBook edition of his popular book Wildcat Cartridges — Reloader’s Handbook of Wildcat Cartridge Design. Gunsmith/author Zeglin explains: “The print edition of Wildcat Cartridges has gone out of print. We have plans to produce a second edition, but that is currently on the back burner. Demand of this book has remained strong so the decision to offer the first edition in a e-book format was made.” The Kindle eBook edition retails for $9.99 on Amazon.com. You can preview a FREE SAMPLE of the book to “try before you buy”.
This is more than just a history of cartridges. Dimensional drawings and loading data accompany many cartridge descriptions. More recent/popular designs are included as well as “classic” older wildcats. There are chapters about important cartridge designers like P.O. Ackley, Jerry Gebby, Rocky Gibbs, and Charles Newton. (The hardback edition of the book contains 288 pages of stories, illustrations, instructions, and data.)
Gunwriter Wayne Van Zwoll says Zeglin’s book is a valuable resource: “Fred has illustrated his book well, with neat line drawings and photos you probably won’t find anywhere else. It’s a rare technical treatise that draws you in with illustration, or that keeps you with an easy flow of chat that, were it lifted from print, might pop up at any gun counter or handloading bench. Fred Zeglin has done well with this book, giving wildcatters – indeed, all rifle enthusiasts – an overview of a culture often mentioned but little explored on the page.”
Writing about the 2005 Print Edition of Wildcat Cartridges, Big Bore Journal declared: “This is a fantastic book on American wildcats, U.S. loads and much more. A must have for wildcatters and gunsmiths.”
We know many of our readers aren’t 100% clear on the difference between a secant ogive bullet and a tangent ogive bullet. Add the “blended” or “hybrid” ogive into the design equation and you add to the confusion. In this article, Berger Ballistician Bryan Litz, explains the characteristics of the three popular ogive types: tangent, secant, and hybrid.
In discussions of ballistics, you’ll see references to “tangent” and “secant” bullet shapes. For many readers, these terms can be confusing. To add to the confusion, bullet makers don’t always identify their projectiles as secant or tangent designs. This article provides a basic explanation of tangent and secant designs, to help you understand the characteristics of both bullet shapes.
Tangent vs. Secant vs. Hybrid
Most match bullets produced today use a tangent ogive profile, but the modern VLD-style bullets employ a secant profile. To further complicate matters, the latest generation of “Hybrid” projectiles from Berger Bullets feature a blended secant + tangent profile to combine the best qualities of both nose shapes. The secant section provides reduced drag, while the tangent section makes the bullet easier to tune, i.e. less sensitive to bullet seating depth position.
Berger Bullets ballistician Bryan Litz explains tangent and secant bullet ogive designs in a glossary section of his Applied Ballistics website, which we reprint below. Bryan then explains how tangent and secant profiles can be combined in a “hybrid” design.
How Bullet Ogive Curves are Defined
While the term “ogive” is often used to describe the particular point on the bullet where the curve reaches full bullet diameter, in fact the “ogive” properly refers to the entire curve of the bullet from the tip to the full-diameter straight section — the shank. Understanding then, that the ogive is a curve, how is that curve described?
LITZ: The ogive of a bullet is usually characterized by the length of its radius. This radius is often given in calibers instead of inches. For example, an 8 ogive 6mm bullet has an ogive that is a segment of a circular arc with a radius of 8*.243 = 1.952”. A .30-caliber bullet with an 8 ogive will be proportionally the same as the 8 ogive 6mm bullet, but the actual radius will be 2.464” for the .30 caliber bullet.
For a given nose length, if an ogive is perfectly tangent, it will have a very specific radius. Any radius longer than that will cause the ogive to be secant. Secant ogives can range from very mild (short radius) to very aggressive (long radius). The drag of a secant ogive is minimized when its radius is twice as long as a tangent ogive radius. In other words, if a tangent ogive has an 8 caliber radius, then the longest practical secant ogive radius is 16 calibers long for a given nose length.”
Ogive Metrics and Rt/R Ratio
LITZ: There is a number that’s used to quantify how secant an ogive is. The metric is known as the Rt/R ratio and it’s the ratio of the tangent ogive radius to the actual ogive radius for a given bullet. In the above example, the 16 caliber ogive would have an Rt/R ratio of 0.5. The number 0.5 is therefore the lowest practical value for the Rt/R ratio, and represents the minimum drag ogive for a given length. An ogive that’s perfectly tangent will have an Rt/R ratio of 1.0. Most ogives are in between an Rt/R of 1.0 and 0.5. The dimensioned drawings at the end of my Applied Ballistics book provide the bullets ogive radius in calibers, as well as the Rt/R ratio. In short, the Rt/R ratio is simply a measure of how secant an ogive is. 1.0 is not secant at all, 0.5 is as secant as it gets.
Hybrid Bullet Design — Best of Both Worlds?
Bryan Litz has developed a number of modern “Hybrid” design bullets for Berger. The objective of Bryan’s design work has been to achieve a very low drag design that is also “not finicky”. Normal (non-hybrid) secant designs, such as the Berger 105gr VLD, deliver very impressive BC values, but the bullets can be sensitive to seating depth. Montana’s Tom Mousel has set world records with the Berger 105gr VLD in his 6mm Dasher, but he tells us “seating depth is critical to the best accuracy”. Tom says a mere .003″ seating depth change “makes a difference”. In an effort to produce more forgiving high-BC bullets, Bryan Litz developed the hybrid tangent/secant bullet shape.
Bryan Litz Explains Hybrid Design and Optimal Hybrid Seating Depths
MidwayUSA is running a big sale on Factory Second and Blemished Bullets. These bullets normally perform just as well as regular bullets, but they may have water spots or other cosmetic defects. MidwayUSA has a very large selection of seconds/blem bullets on sale for both rifles and pistols. Here are some of the best deals we found among the quality varmint and match rifle bullets. All these selections are discounted 30%:
To learn more about how ambient temperature (and primer choice) affect pressures (and hence velocities) you should read the article 
We know many of our readers aren’t 100% clear on the difference between a secant ogive bullet and a tangent ogive bullet. Add the “blended” or “hybrid” ogive into the design equation and you add to the confusion. In this article, Berger Ballistician Bryan Litz, explains the characteristics of the three popular ogive types: tangent, secant, and hybrid.
Hybrid Bullet Design — Best of Both Worlds?
