December 5th, 2017

Competition Hardware — The Modern F-Open Rifle

.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

Emil Kovan is one of the top F-Class shooters in the world. He won the 2014 United States F-Open Championship. Earlier this month Emil finished second in F-Open Division at the 2016 Canadian National F-Class Championship in Ontario. Emil actually tied Open-class winner Shiraz Balolia for overall score AND “V”-count, but Emil was awarded second on the tie-breaker.

The Anatomy of a Modern F-Class Open Rifle

Report by Emil Kovan
Kovan Match Rifles LLC, www.matchrifles.com

“What are the best components for an F-Open class rifle, and why?” That’s a question that I get asked all the time and will try to answer in this article. Two months ago, I was contacted by Duane, a gentleman I met at the 2015 F-Class Nationals. He was interested in building a rifle with the new Master Class Low Profile F-Open Stock, created by Carl Bernosky and Alex Sitman of Master Class Stocks.

I have known Alex Sitman for many years, and use his stocks exclusively, but was not very familiar with his new Low Profile F-Open stock. After a brief conversation with Alex, I placed an order, and had the stock inletted and bedded at my shop in a month. My first impression was “Wow that’s a long stock” — the forearm is significantly longer than on the original Master Class F-Class prone stock. I bolted the barreled action in, and squeezed the end of the forearm and barrel together, the stock flexed a little bit, but not as much as other designs that I have tested. I think that’s due to having “more meat” in the receiver area. The full stock depth continues farther forward that on some other “low profile” designs. That makes the stock stiffer in the vertical plane, reducing the hinging effect forward of the action. The stock was finished in gloss black per the customer’s request. Interestingly, I found that the multiple layers of paint and clearcoat stiffened the stock up quite a bit.

CLICK IMAGE below for full-screen version
.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

Low Center of Gravity Tames Torque
Compared to the original Master Class F-Open stock, the barrel sits about an inch lower. Lower center of gravity equals less torque, and that is very important when shooting heavy bullets in fast twist barrels. Another significant improvement is that the toe of the stock is flat and parallel to the forearm. I added a 3/4″ track rail in the rear, and milled the underside of the fore-end to create two parallel “rails” in the front to help the stock track better.

One of the biggest reasons why I like Master Class stocks, is the pistol grip. I don’t shoot “free recoil” and a comfortable pistol grip is super important to me when selecting a stock. The new Master Class Low Profile stock shares the same grip as the old model. This allows the stock to accommodate either a “hard hold” style or a more free-recoil style of shooting — whatever the rifle’s owner prefers. This design versatility is one reason I recommend Master Class stocks. Shooters may experiment with either shooting style to find what suits them best.

.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

Cartridge Choice — A 40° .284 Win Improved
Duane decided to have the barrel chambered for my 284 KMR IMP (Improved) wildcat. What is .284 KMR IMP and why choose it over the straight .284 Winchester? Improved by definition means “made better”, I took a great cartridge, and modified it to increase capacity, reduce pressure, and increase brass life.

There are many “improved” variants of the original .284 Winchester: 7mm Walker, .284 Shehane, .284 Ackley and so on. My version, the 284 KMR IMP, shares the .010″ blown-out sidewalls of the .284 Shehane, but I have further increased the case capacity by changing the shoulder angle from 35 to 40 degrees. The 284 KMR IMP allows you to almost match magnum cartridge velocity in a standard-bolt-face action. If you want to run 180gr-class 7mm bullets over 2900 FPS, it is cheaper and more convenient to have a barrel chambered in 284 KMR IMP than to spend $650 for a magnum bolt.

Tuning Loads for the .284 Win Improved Cartridges
The 284 KMR IMP seems to have two nodes, one around 2820 fps and other at 2940 fps. My match load clocks at 2935 fps with single-digit ES. Note –I selected that load based on accuracy, NOT raw speed. A lot of novice (or hard-headed) shooters make the mistake to push their cartridges to the max, and disregard more accurate loads at lower velocity.

.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

The sport of F-Class is rapidly growing, and the equipment used is improving constantly. I remember that only few years ago, an F-Open rifle that could shoot sub-one-inch of vertical at 300 yards was considered competitive. Now, we are pursuing sub-one-inch vertical at 600 yards! It takes a great rifle to approach that goal, but it is also up to the shooter to learn and experiment as much as possible in order to achieve success.

Dies for an Improved .284 Win Cartridge
One of the biggest challenges in campaigning a wildcat cartridge has been obtaining great dies. When searching for custom dies, it almost seems like that the odds are stacked against us. The most common problem is wait-time — custom die orders can take months to be completed. Also, most custom die makers want you to send them two or three cases, each fire-formed three times. I find that funny because if could somehow properly size the cases for three fire-forming cycles, I would not need a sizing die.

.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

Custom-made dies should size the case just right, but sometimes the die’s internal dimensions are slightly off, and this leads to problem number two: dies sizing too much (or even worse) too little. I had a one “custom” die that would not size the bottom of the case enough. This made the extraction of fired cases very difficult. I feel that the best option (if available) for shooters interested in wildcat chambers is to have their gunsmiths make the dies. I offer that die-making service in addition to barrel chambering.

BAT Machine “M” Action
Duane decided to use a BAT M action for this rifle, and I think that he could not have made a better choice. We are blessed with many good match-quality receivers: Barnard, BAT, Borden, Kelbly, Nesika, and Stiller just to mention a few. These are all very well-made and suitable for F-Class. Among BAT Machine Co.actions, I like BAT models M, MB, and 3LL best. I prefer these because because of their size (large bedding footprint) smoothness, timing, options available, and last but not least visual appearance.

Trigger: I recommend and use Jewell triggers. Other good options are: Kelbly, CG Jackson (good 2-Stage) Anschutz (best 2-Stage for Bat and Kelbly actions), Bix’N Andy, and David Tubb.

Barrel: Duane made another good choice here. He decided to go with a Brux 1:8.5″-twist, 4-groove cut-rifled barrel. If you look at the F-Class and Long Range benchrest equipment lists, you will see that cut-rifled barrels are currently dominating. Many records have been shot with both button-rifled, and cut-rifled barrels. I have shot both, and prefer cut-rifled barrels. I am not saying that button-rifled barrels are not capable of shooting as well as cut-rifled barrels, but on average, in my experience, four out of five cut-rifled barrels (from top makers) will shoot well, vs. three out of five buttoned barrels. YMMV, but this is what I’ve observed.

Brux Barrels is not the only company that produces very accurate cut-rifled barrels. We know that Krieger, Bartlein, Satern, and Hawk Hill Custom all make fine cut-rifled barrels as well.

Scope: Duane’s rifle was fitted with a Nightforce 15-55x52mm Competition scope with DDR-2 reticle. This optic is ultra clear, reasonably lightweight (28 oz.), super reliable, and has 1/8 MOA clicks — what you want for long range F-Class competition. In this 15-55X NF model, I like the DDR-2 reticle best, because fine cross hairs (FCH) are hard to see in heavy mirage. The DDR-2 has a heavier horizontal line, with a center dot. March scopes are also very popular and very well-made.

.284 Win F-Class F-Open Rifle Emil Kovan Brux BAT M Master Class Bernosky

Thanks for reading, and keep ‘em in the middle…

Emil Kovan F-Class competition bio photoEmil Kovan Competition History:

– 2014 F-Class Open National Champion

– 2016 F-Class Open Canadian Championship, Silver Medal (tied for first on score)

– 2015 F-Class Open National Championship, Silver Medal

– F-Class Open National Championship Teams, 2015, 2014, 2013, Shooting Team Member

– Over 15 wins in Regional and State Championships in Palma, F-TR, F-Open

– 2013 U.S. National Team Member

– 2017 U.S. National Development Team Member

Permalink - Articles, Competition, Gunsmithing 6 Comments »
December 5th, 2017

Ballistics Linguistics: Bullet “Caliber of Ogive” Defined

Sierra Caliber of Ogive Bullet Sierra BC geometry

This article, which originally appeared in the Sierra Bullets Blog, provides a new terminology that helps describe the geometry of bullets. Once you understand the meaning of “Caliber(s) of Ogive”, you can quickly evaluate potential bullet performance by comparing listed Caliber of Ogive numeric values.

by Mark Walker, Sierra Bullets New Product Development Manager
During one of our recent product releases, we listed the “caliber of ogive” of the bullet in the product description. While some understood what that number meant, it appears that some are not aware of what the number is and why it is important. In a nutshell, the “caliber of ogive” number will tell you how sleek the front end of the bullet is. The higher the number is, the sleeker the bullet. It also makes it easy to compare the ogives of different caliber bullets. If you want to know if a certain .308 caliber bullet is sleeker than a 7mm bullet, simply compare their “caliber of ogive” numbers.

So exactly how do you figure “caliber of ogive”? If you look at the drawing of the .30 caliber 175 gr HPBT bullet #2275 (at top), you will see that the actual radius of the ogive is 2.240. If you take that 2.240 ogive radius and divide by the diameter (or caliber) of the bullet you would get 7.27 “calibers of ogive” (2.240 ÷ .308 = 7.27). (See top photo).

In a nutshell, the “caliber of ogive” number will tell you how sleek the front end of the bullet is. The higher the number is, the sleeker the bullet.

Next let’s look at the print (below) of our 6.5mm 142gr HPBT #1742 bullet for comparison. The actual radius of the ogive is 2.756. Like with the .30 caliber 175 gr HPBT bullet #2275, if you divide 2.756 by the diameter (or caliber) of the bullet you get 10.44 “calibers of ogive”.

Sierra Caliber of Ogive Bullet Sierra BC geometry

As most people know, it has been determined through testing that the 6.5mm 142gr HPBT #1742 has a significantly higher ballistic coefficient than the .30 caliber 175 gr HPBT bullet #2275. However by simply comparing the “caliber of ogive” number of each bullet you can easily see that the 6.5mm 142 gr HPBT #1742 is significantly sleeker than the .30 caliber 175 gr HPBT bullet #2275 even without firing a shot.

Some people would say why not just compare the actual ogive radius dimensions instead of using the “caliber of ogive” figure. If we were comparing only bullets of the exact same diameter, then that would be a reasonable thought process. However, that idea falls apart when you start trying to compare the ogives of bullets of different diameters. As you can see with the two bullets presented above, if we compare the actual ogive radius dimensions of both bullets the difference is not much at all.

However, once again, testing has shown that the 6.5mm 142 gr HPBT #1742 has a significantly higher BC. The only way that this significant increase shows up, other than when we fire the bullets in testing, is by comparing the “caliber of ogive” measurement from both bullets.

Hopefully this will help explain what we mean when we talk about “caliber of ogive” and why it’s a handy number to use when comparing bullets. This information will help you to make an informed decision the next time you are in the market to buy bullets.

Sierra Bullets Caliber of Ogive Bullet BC SMK

Story tip from Grant Ubl. We welcome reader submissions.
Permalink Bullets, Brass, Ammo, Reloading 5 Comments »