Building a 300 Winchester Magnum Precision Rifle

I am a huge 300 Winchester Magnum fan.  I took a hacksaw and Sawzall to one in 300 Winchester Magnum: How Does Barrel Length Change Velocity- A 16″ 300 Win Mag?  And if that wasn’t ridiculous enough, I went and installed a brake on the gun for Does size matter? Custom Remington 700 16.5″ 300 Winchester Magnum follow up (FYI, my teeth and head still hurt from that one).

Sure, you can get similar external ballistics in a light recoiling 6mm or 6.5mm cartridge, but nothing smacks steel the way a big .30 caliber rifle does.  It’s in use by the U.S. Military (cool) and with the right load, it can rival the 338 Lapua Magnum at long range.  Reloading components, including quality Norma brass, factory hunting and match grade ammunition are readily available.  While it will pelt the shooter when chambered in a 6 pound hunting rifle, in a heavy rifle, recoil is manageable.

I ordered the following items from Brownells:

• Blackheart International belted magnum long action receiver (100-005-693)
• Accuracy International AICS AX 2.0 chassis 
• Viper’s Venom cutting oil (100-013-368)
• Manson 300 Winchester Magnum finish reamer (513-050-380)
• Manson belted magnum go and nogo gauges (513-100-320)
• 3/8″ High-speed steel turning kit (080-000-835)
• High-speed steel 35 degree profile kit (080-000-836)
• 1/2″ threader (080-000-839)
• Starrett Dial indicator (749-007-761)
• Badger FTE muzzle brake (093-000-040)
• Spuhr 34mm IDEAL mount (100-011-208)
• Nightforce ATACR 5-25 SFP Mil/Mil (100-012-575)
• Jewell HVR trigger (100-002-559)

Bartlein Barrels supplied a tight-bore barrel for this project.  Bartlein’s 30 caliber tight-bore barrels have a bore diameter of .298-.299″ (ours is .299″), versus .300″ in a standard bore.  The groove diameter is similar, .3065-.3080″in the tight-bore .30 caliber, versus .308″ in the standard.  Tight-bore barrels are very popular in Palma matches, with shooters often reporting increased velocity over a standard bore diameter.

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The use of a custom action and chassis system greatly simplifies construction of this rifle.  If this was a factory Remington 700 action, I would blueprint the action (article: Blueprinting a Remington 700 Action) and install an external bolt stop.  Neither of these operations are required with a precision action like this.  Likewise, if I were using a fiberglass stock, such as a McMillan A5, I would be have to bed the barreled action into it.  With the AICS AX 2.0 chassis, this isn’t required.

I’ve mentioned this elsewhere, but it bears repeating.  I’ve chambered barrels many ways, and I think each system has its advantages and disadvantages .  Currently, I dial in both ends of the barrel through the head stock of the lathe. Without actually trying a few different methods, don’t believe that one way is superior purely because someone put it in a video.  Actually try different methods and see what works for you.

I turn the barrel at 360 RPM, thread at 220 RPM and ream the chamber at 70 RPM.  My preferred lubricant is Viper’s Venom cutting oil.

I chambered this barrel before I built my pressurized flush system.  I take light cuts at 70 RPM, stopping the lathe, retracting the reamer, cleaning and re-lubricating it every .025″ or so.   I’ve tried pre-drilling chambers, and running a boring bar to remove material and it works well, but, I wasn’t in a rush.

Off to paint- in this case; Cerakote, graphite black.  An overview of how I coat my rifles can be found here, Cerakote firearm refinishing.

I selected the excellent Jewel HVR trigger for this rifle.  The Jewel is a very nice target trigger.  It does have a lot of screws and e-clips on it: I do not recommend it for heavy field use.

Since the rifle is sitting in an Accuracy International AICS AX 2.0 chassis, the stock work is completed once the barreled action is bolted in.    The optic is a Nightforce ATACR 5-25 Mil/Mil SFP scope mounted in a Spuhr ISMS.

Final assembly parts:

• Badger FTE muzzle brake (093-000-040)
• Spuhr 34mm IDEAL mount (100-011-208)
• Nightforce ATACR 5-25 SFP Mil/Mil (100-012-575)
• Accuracy International AICS AX 2.0 chassis 
• Sierra 7 bipod  (100-013-079)
• Jewell HVR trigger (100-002-559)

You maybe wondering about the Aimpoint T1 red dot sight on the Spuhr ISMS mount: it’s there to quickly find targets when the ATACRs magnification is dialed up (narrow field of view).

For initial load development, I worked up some loads with virgin Norma brass, H1000 powder, WLRM primers and the 208 A-Max. All shooting was done prone, from a bipod with a rear bag.

Load	Bullet	Powder	MV FPS	SD	Shots	Distance (yards)	Size (inches)
1	208 A-Max	H1000	2628	8.5	3	100	.421
2	208 A-Max	H1000	2672	16.3	3	100	.538
3	208 A-Max	H1000	2714	15.8	3	100	.412
4	208 A-Max	H1000	2735	14.1	3	100	.897
5	208 A-Max	H1000	2753	17.6	5	100	.402
Fed 190 Gold Medal	190 SMK		2908	16.1	5	100	.999

For what it’s worth, in my mind, I don’t weigh 3-round groups as heavily as 5-round groups.  I think they are functional for load development and determining if a rifle can shoot: however, I try to shoot 5 or 10-round groups as load development progresses to fully evaluate a rifle and cartridge combination.

The rifle, as shown above, weighs 18.14 pounds: Yikes!  The up side to big and heavy, is very manageable recoil in a belted magnum.

I am quite pleased with the initial results.  I’ve done further testing and load development with the 210 SMK and will be posting about it soon.