February 2nd, 2020

Sunday GunDay: Nat’l Champion F-Open Rifle and Cerus Twin

Brian Bowling F-Class F-0pen Open National Champion Brian Blake Barrel Blake Machine .284 Winchester Win RAHM rifle competition

With the Berger Southwest Nationals commencing this week, we thought our readers would appreciate a showcase of two impressive, state-of-the-art F-Open match rifles. The first, show above, is the .284 RAHM (40° .284 Win Imp) with which Brian Bowling captured the 2019 F-Class Open Division Long Range National Championship. The second rifle belongs to barrel-maker Bryan Blake. Like Bowling’s rifle, Blake’s rig features a low-profile Cerus stock, but with purple highlights. Both rifles have 6-groove, cut-rifled barrels from Blake Barrel & Rifle and both sport Nightforce scopes.

Brian Bowling F-Class F-0pen Open National Champion Brian Blake Barrel Blake Machine .284 Winchester Win RAHM rifle competition

Twin World-Class F-Open Rifles

Report from Bryan Blake of Blake Barrel & Rifle
We had been producing gun barrels for about 1.5 years prior to the 2019 NRA Long Range F-Class Nationals. Brian Bowling started shooting our 7mm barrels in May of 2019. Bowling and I are both on the Rutland team, Team Cerus, which has seven members. Bowling and I received the first Cerus XL stocks from Cerus Rifleworks in August of 2018. The stock was a very straight design.

With our barrels, these F-Open rigs can shoot! In 2018, Brian Bowling and I had the only two clean scores for the first match at the 1000-yard team NRA Nationals. In spring of 2019, I worked with Will of Cerus Rifleworks to see if we could come up with a lower center of gravity design to enhance what was already the straightest stock out there. We developed the Cerus XR stock which features stepped metal rails on the fore-end. I cut my XL Cerus stock and designed the rail system attached to the sides of the fore-end. Bowling’s stock (with black rails) was the second XR in the shooting world. On his very first weekend match at 600 yards he shot a 200-20X with the new XR stock and Blake 7mm 1:8.5″-twist barrel. He was using Berger 184gr 7mm bullets.

Brian Bowling F-Class F-0pen Open National Champion Brian Blake Barrel Blake Machine .284 Winchester Win RAHM rifle competition

In 2019, at the NRA F-Class Long-Range Nationals, Brian Bowling won the F-Open National Championsship with a strong performance. He finished with a ton of Xs, three points ahead of the second place competitor. Before Brian’s impressive victory, we were told by many top shooters that a 6-groove barrel has never won any F-Class Mational event, and hypothetically never would. Well with Brian Bowling’s excellent shooting and reloading capabilities, we achieved a feat many said couldn’t be done.

Brian Bowling F-Class F-0pen Open National Champion Brian Blake Barrel Blake Machine .284 Winchester Win RAHM rifle competition

Bowling’s Championship-winning rifle features a Bat Model B action in the Cerus XR stock. His Blake barrel is chambered for the .284 RAHM wildcat cartridge. This is a 40-degree (40°) version of the .284 Winchester. The .284 RAHM has a straighter case body compared to the original .284 Win.

We built Bowling’s rifle, doing everything except the final clear finish. We can do that work, but were short on time for the Nationals last year. We are proud of the chambering work we do and the quality of our bedding jobs.

Brian Bowling F-Class F-0pen Open National Champion Brian Blake Barrel Blake Machine .284 Winchester Win RAHM rifle competition

Bryan Blake’s F-Open Rifle — the Purple XR

Brian Bowling F-Class F-0pen Open National Champion Brian Blake Barrel Blake Machine .284 Winchester Win RAHM rifle competition

The Purple XR-stocked gun I shoot was built in August of 2019, right before the 2019 NRA F-Class Nationals. The natural wood is complimented by highlights finished with a bright purple metallic epoxy resin that Will from Cerus dreamed up. For this rifle we mated a BAT 3LL action with Blake barrels (switch-barrel configuration). Up front the fore-end rails are painted purple “plum crazy” to match the purple resin. The purple XR is finished with automotive “high solids” clear-coat, and block-sanded for a smooth, flawless look.

Brian Bowling F-Class F-0pen Open National Champion Brian Blake Barrel Blake Machine .284 Winchester Win RAHM rifle competition

Blake’s Rifle is a Switch Barrel — 7mm and .30 Caliber
This Purple XR was set up to be a switch barrel rig, with both a 7mm BBM and a .30 BBM*. These BBM wildcats are based on shortened and straightened .300 WSM with a 40-degree shoulder. On my purple XR rifle as well as Bowling’s rifle, we employ Nightforce optics and load Berger bullets. These are the only glass and projectiles we use in our rifles.

The Purple XR is extremely accurate. Check out this 2.6″ group, shot at 1000 yards during a club match at the Ben Avery Range in Arizona. Yes, that is 1/4-MOA at 1K! Many folks would be very happy with that group at 600 yards. At 1000 yards it is remarkable. No, the rifle can’t do that every time. But this does demonstrate that the Purple XR is a tack-driver. CLICK HERE to see a 3.9 inch, 15-shot group at 1000 yards on the F-Class target (150-15X).

Brian Bowling F-Class F-0pen Open National Champion Brian Blake Barrel Blake Machine .284 Winchester Win RAHM rifle competition

Brian Bowling F-Class F-0pen Open National Champion Brian Blake Barrel Blake Machine .284 Winchester Win RAHM rifle competition

About Blake Barrel and Rifle — History and Barrel-Making Process
Blake Barrel and Rifle was re-launched in 2018. The business was actually started by my grandfather, Robert Blake, in 1966. In 1969 my grandfather stopped doing gunsmithing and making single-point cut-rifled barrels. He transitioned to doing industrial work, and less work for the public. After all those years he and my father, Dave Blake, kept the barrel-making equipment in storage. They kept the gun-drilling machines in the shop as they used them to drill long, deep holes in anything from aircraft parts to electric motor rotors.

In 2012 we got the diamond single-point, sine-bar rifling machine out of storage, along with the Pratt and Whitney double-spindle reaming machine. We then completely rebuilt and updated the equipment. We modified the gun-drill to be a counter-rotating drilling system. What that means is the drill spins at about 20% of the rotational speed, and the barrel at 80%. The counter-rotation keeps the drill on the center axis of the barrel more precisely than just rotating the barrel, or just rotating the drill. We are able to consistently drill holes in our barrel steel (primarily 416R) that at the end of a 33.25″ blank that is only .005″ off of center axis.

We then ream the barrels to be .0004″ below desired finish bore size. After the reaming process we mandrel-hone the bores to be .0001″ below finish bore size. This process eliminates reamer marks in the barrel bore. Therefore very minimal lapping is needed after rifling to remove any tooling marks. We then rifle the barrel to any twist rate we like. With a fine lap after rifling, the barrel has no tooling marks and all surface metal is flowing in the direction of the twist of the rifling.

* 7mm BBM stands for “Blake Bramley Magnum”. Dan Bramley and I developed that cartridge together in October of 2017. The .30 BBM is the “Blake Barrel Magnum”, which I developed in May of 2018.

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February 2nd, 2020

How Powder Moisture Content Affects Pressure and Speed

vihtavuori vv moisture content powder propellent
This Technical Report Comes from the Vihtavuori website.

Powder Moisture Content — Did You Know?
Variations in moisture content change the burning rate of a powder and thereby chamber pressures and muzzle velocity. The moisture content of the Vihtavuori N100 and N300 series powders is usually around 1%, while the N500-series’ normal moisture content is 0.6% because of the added nitroglycerine.

So what difference does moisture content make? Here’s an example. In a test, a [Vihtavuori] powder sample was dried by heating it, losing about 0.5 % of its weight. Cartridges were then loaded with the dried powder and fired using a pressure gun. Chamber pressures and muzzle velocities produced by these special cartridges were compared to those produced by cartridges loaded with untreated powder. (The powder charge and bullet were of course the same in both sets of cartridges.)

After Powder Drying:
Pressure Increased 11% from 320 MPa to 355 MPa
Velocity Increased 2.6% from 2526 to 2592 FPS

Comparing results showed chamber pressures increased from 320 MPa to 355 MPa with the dried powder, and the muzzle velocity increased accordingly from 770 m/s to 790 m/s (2526 to 2592 FPS). And note, this is only one example, of one caliber and loading. The difference might be much higher depending on the cartridge and loading combinations.

Recommendation: Store powder below 68°F in 55-65% humidity.

What does this tell us? Well, it seems we need to forget the old saying “Keep your powder dry”! Instead, focus on proper powder storage, at a temperature below 20°C/68°F and humidity between 55 and 65%. Safe reloading everybody!

vihtavuori vv moisture content powder propellent

Tech Tip sourced by EdLongrange. We welcome reader submissions.
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February 2nd, 2020

Barrel Twist Rate — How to Determine the True Twist Rate

FirearmsID.com barrel rifling diagram
Erik Dahlberg illustration courtesy FireArmsID.com.

Sometimes you’ll get a barrel that doesn’t stabilize bullets the way you’d anticipate, based on the stated (or presumed) twist rate. A barrel might have 1:10″ stamped on the side but it is, in truth, a 1:10.5″ twist or even a 1:9.5″. Cut-rifled barrels, such as Kriegers and Bartleins, normally hold very true to the specified twist rate. With buttoned barrels, due to the nature of the rifling process, there’s a greater chance of a small variation in twist rate. And yes, factory barrels can be slightly out of spec as well.

After buying a new barrel, you should determine the true twist rate BEFORE you start load development. You don’t want to invest in a large supply of expensive bullets only to find that that won’t stabilize because your “8 twist” barrel is really a 1:8.5″. Sinclair International provides a simple procedure for determining the actual twist rate of your barrel.

Sinclair’s Simple Twist Rate Measurement Method
If are unsure of the twist rate of the barrel, you can measure it yourself in a couple of minutes. You need a good cleaning rod with a rotating handle and a jag with a fairly tight fitting patch. Utilize a rod guide if you are accessing the barrel through the breech or a muzzle guide if you are going to come in from the muzzle end. Make sure the rod rotates freely in the handle under load. Start the patch into the barrel for a few inches and then stop. Put a piece of tape at the back of the rod by the handle (like a flag) or mark the rod in some way. Measure how much of the rod is still protruding from the rod guide. You can either measure from the rod guide or muzzle guide back to the flag or to a spot on the handle. Next, continue to push the rod in until the mark or tape flag has made one complete revolution. Re-measure the amount of rod that is left sticking out of the barrel. Use the same reference marks as you did on the first measurement. Next, subtract this measurement from the first measurement. This number is the twist rate. For example, if the rod has 24 inches remaining at the start and 16 inches remain after making one revolution, you have 8 inches of travel, thus a 1:8 twist barrel.

Determining Barrel Twist Rate Empirically
Twist rate is defined as the distance in inches of barrel that the rifling takes to make one complete revolution. An example would be a 1:10″ twist rate. A 1:10″ barrel has rifling that makes one complete revolution in 10 inches of barrel length. Rifle manufacturers usually publish twist rates for their standard rifle offerings and custom barrels are always ordered by caliber, contour, and twist rate. If you are having a custom barrel chambered you can ask the gunsmith to mark the barrel with the twist rate.

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