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July 11th, 2015
Article by Bill, Editor of Rifleshooter.com
A few years ago I built a custom switch-barrel Remington 700 on an AICS Chassis chambered in .243 Winchester and .308 Winchester. I found the .243 Win finicky during load development and started looking at other options for the 6mm Bartlein 1:8″-twist HV barrel.
 Initially drawn to the 6mmBR and 6mm Dasher, I realized these cartridges wouldn’t feed from an AICS magazine system without extensive modification. I took a look at the 6mm Creedmoor, 6XC, and 6mm-6.5×47 Lapua (aka 6×47 Lapua), all of which feed well from a detachable magazine. At right you can see the 6×47 Lapua in an AICS magazine. It has the “Goldilocks factor” — not too long, not too short.
The ability to simply convert 6.5×47 Lapua brass to 6×47 brass by running the parent 6.5mm brass through a full-length Forster sizing die in a single step was what made me choose the 6×47 Lapua over the 6mm Creedmoor and 6XC (both excellent cartridges in their own right). I also own a 6.5×47 Lapua rifle, so I had a supply of 6.5×47 brass ready to neck-down. Being able to create 6×47 brass easily (one pass and done) was very appealing.
Left to right, below: 6mmBR, 6-6.5×47 Lapua, 6.5×47 Lapua, and .243 Winchester.
I cut the chamber end off my .243 Win barrel, threaded and chambered my rifle for the 6×47 Lapua cartridge. I have written a lengthy article on this cutting and re-chambering process. Home gunsmiths interested in this process can READ MORE HERE.
When the re-chambering was complete, I headed to the range and worked up a set of eight loads using Berger 108 BTHPs, H4350, Lapua brass, and CCI 450 primers.
Load development was a little trickier than with the 6.5×47 Lapua parent cartridge. The accuracy nodes were smaller. However, once I dialed in a load with Hodgdon H4350 and the 108-grain Berger BTHP, the rest was history. The 6×47 rig is now one of the most consistent rifles I own, holding just above 0.3 MOA for 5-round groups. Below is a 100-yard test target with 108-grain Berger BT in the 6×47 Lapua. Five-shot group sizes are (L to R): .369″, .289″, and .405″. The average size was .354″ or .338 MOA. [Editor: We think that is excellent accuracy for a tactical-type rifle shot from bipod.]
Learn More about this 6×47 Lapua Project
I’ve written more about this 6×47 rifle on my Rifleshooter.com website. To learn more about my experience with the 6×47 Lapua, click this link: 6-6.5X47 Lapua Review.
About the author: Bill has been a serious shooter for over 20 years. A former Marine Corps Sergeant, he’s competed and placed in High Power Rifle, ISPC, USPSA, IDPA, 3-Gun, F-Class, and precision rifle disciplines. In addition to being an NRA-certified firearms instructor and range officer, Bill has hunted big game in North America, South America, and Africa. Bill writes extensively about gunsmithing, precision rifles, and the shooting sports on his blog, Rifleshooter.com.
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July 9th, 2015
Barrel nut system allows “Pre-Fit” barrel installation on a Remington action. CLICK photo to zoom.
REMAGE Project Report by Bill, Rifleshooter.com Editor
Installing a new barrel on your Remington 700 (especially without a lathe) may seem like a daunting task, but thanks to companies like McGowen Precision Barrels, there are easier alternatives. By adopting a Savage-style barrel nut on a 1 1/16″ thread for a Remington 700 receiver, pre-chambered (aka “pre-fit”) barrels can be easily swapped with just a few hand tools. This system is sometimes called a REMAGE conversion (for “REMington savAGE”).
Using a few tools from Brownells: Remington 700 Action Wrench, Barrel Vise, Go and No-Go Gauges, Recoil Lug Alignment Tool, and a Savage Barrel Nut Wrench, I was able to swap the .308 Winchester barrel off of my Remington 700 short action and install the new McGowen pre-fit, pre-chambered barrel, converting it to a tack-driving 6BR (aka 6mmBR Norma).
The existing barrel is simply removed from the action (normally the hardest part) and the new barrel is screwed on with the Go Gauge in place. The barrel nut is tightened against the action, headspace verified with the Go Gauge, and you are off to the range. It takes all of the machine work out of the barreling process. Note: the barrel nut has a slightly larger diameter and some stocks may require minor inletting. Also if you are shooting fired brass from another rifle with the same chambering, you should FL-size the brass before loading it for your new pre-fit barrel.
My McGowen Remage barrel looks and shoots great. I’ve written two longer articles that provide greater detail about this project. To learn more about how the barrel was installed, read: Rebarrel a Remington 700 without a lathe: McGowen’s Remage barrel conversion. To see how the rifle performed at the range, read: McGowen Remage Barrel Review: Spoiler Alert- It Shoots!.
Bill has been a serious shooter for over 20 years. A former Marine Corps Sergeant, he’s competed and placed in High Power Rifle, ISPC, USPSA, IDPA, 3-Gun, F-Class, and precision rifle disciplines. In addition to being an NRA-certified firearms instructor and range officer, Bill has hunted big game in North America, South America, and Africa. Bill writes extensively about gunsmithing, precision rifles, and the shooting sports on his blog, Rifleshooter.com.
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July 5th, 2015
We know our readers are curious about the new Tipped MatchKings (TMKs) introduced by Sierra Bullets this year. Our friend Bill at Rifleshooter.com got hold of some of the .30-Cal 175-grain TMKs and tested them in his .308 Win rifle. He found the bullets were very consistent in weight. As for bearing surface, the SD was fairly low (.002″), but measurements varied from 0.400″ to 0.407″. Seven-thousandths extreme spread is more than we like to see, as it may affect accuracy. Therefore we recommend you sort by bearing surface length before loading these in match rounds.
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June 4th, 2015
With barrels, one wonders “Can a little more length provide a meaningful velocity gain?” To answer that question, Rifleshooter.com performed an interesting test, cutting a .308 Win barrel from 28″ all the way down to 16.5″. The cuts were made in one-inch intervals with a rotary saw. At each cut length, velocity was measured with a Magnetospeed chronograph. To make the test even more interesting, four different types of .308 Win factory ammunition were chronographed at each barrel length.
READ RifleShooter.com .308 Win Barrel Cut-Down Test Article.
Test Barrel Lost 22.7 FPS Per Inch (.308 Win Chambering)
How much velocity do you think was lost, on average, for each 1″ reduction in barrel length? The answer may surprise you. With a barrel reduction from 28″ to 16.5″, the average speed loss of the four types of .308 ammo was 261 fps total. That works out to an average loss of 22.7 fps per inch. This chart shows velocity changes for all four ammo varieties:
Summary of Findings: The average velocity loss per inch, for all four ammo types combined, was 22.7 FPS. By ammo type, the average loss per inch was: 24.6 (Win 147 FMJ), 22.8 (IMI 150 FMJ), 20.9 (Fed GMM 168gr), and 22.5 (Win 180PP).
Interestingly, these numbers jive pretty well with estimates found in reloading manuals. The testers observed: “The Berger Reloading manual says for the 308 Winchester, ‘muzzle velocity will increase (or decrease) by approximately 20 fps per inch from a standard 24″ barrel’.”
How the Test Was Done
The testers described their procedure as follows: “Ballistic data was gathered using a Magnetospeed barrel mounted ballistic chronograph. At each barrel length, the rifle was fired from a front rest with rear bags, with five rounds of each type of ammunition. Average velocity and standard deviation were logged for each round. Since we would be gathering data on 52 different barrel length and ammunition combinations and would not be crowning the barrel after each cut, we decided to eliminate gathering data on group sizes. Once data was gathered for each cartridge at a given barrel length, the rifle was cleared and the bolt was removed. The barrel was cut off using a cold saw. The test protocol was repeated for the next length. Temperature was 47° F.”
CLICK HERE to Read the Rifleshooter.com Test. This includes detailed charts with inch-by-inch velocity numbers, multiple line charts, and complete data sets for each type of ammo. Rifleshooter.com also offers ballistics graphs showing trajectories with different barrel lengths. All in all, this was a very thorough test by the folks at RifleShooter.com.
Much Different Results with 6mmBR and a Longer Barrel
The results from Rifleshooter.com’s .308 barrel cut-down test are quite different than the results we recorded some years ago with a barrel chambered for the 6mmBR cartridge. When we cut our 6mmBR barrel down from 33″ to 28″, we only lost about 8 FPS per inch. Obviously this is a different cartridge type, but also our 6mmBR barrel end length was 5″ longer than Rifleshooter.com’s .308 Win start length. Velocity loss can be more extreme with shorter barrel lengths (and bigger cartridges). Powder burn rates can also make a difference.
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