UPGRADE: Multi-Caliber Rifle Chassis

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The centerline of this .338 Norma Mag case sits in the magazine, allowing the bolt to chamber the round closer to the chamber’s centerline.

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The monopod-equipped stock can fold to the left or right side. When folded to the right, the stock secures the bolt in place.

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Unfold the stock, and the length of pull and cheekpiece height are fully adjustable.

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The multi-caliber rifle chassis’ bottom metal is part of the dedicated action block. this is one of the components that make up the “insert rifle” concept.

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The Picatinny rail enables a repeatable zero when removing/ replacing the scope.

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For the author, the hefty weight of the rifle facilitated fast follow-up shots, even with the high-power .338 Norma Mag load.

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The chassis system is designed so that it can be disassembled with a minimum of tools. Here the operator uses a bullet to disengage the pistol grip from the chassis.

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The hand screw on the bottom of the chassis holds in the “insert rifle.” With the rifle on its butt and the muzzle skyward, removal of insert rifle is simple.

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Vin Battaglia, principal of BML Tool, demonstrates the Multi-Caliber Rifle Chassis. Note the built-in muzzle brake that is compatible with Gemtech suppressors.

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Starting out as a shop in a two-car garage in 1968, BML Tool & Manufacturing is now, over 55 years later, operating out of a 38,000-square-foot facility nestled in the hills of western Connecticut. BML’s roots in tool and die making are deep.

Throughout the facility, you’ll hear tool bits buzz in a wet slurry of cutting fluid as CNC machines reveal familiar shapes from aluminum forgings. Metal stamping machines the size of small buildings pound steel into magazine components.

BML is a precision metal craft vendor that makes critical parts for the military and commercial markets. It is also into small-weapons research and development with an eye on a modular weapon system. Parts manufactured by BML are used in aircraft, medical devices and small arms.

Accurate-Mag
If you are a shooter of ARs and precision tactical rifles, you may have used a weapon with a component manufactured by BML. To say that magazines made by Accurate-Mag, a BML company, are the Cadillacs of rifle magazines is an understatement. Accurate-Mags are single-stack, metal, centerfire-rifle magazines that meet all mil-spec and NATO Stanag requirements. These magazines fit all M24- and M40-type service rifles as well as Mk 13 and NATO variants.

OEM rifle manufacturers like Colt, Savage, Ruger, McMillan, Remington and others use Accurate-Mags. (Look for the Accurate-Mag cartouche on the magazines for Ruger’s Gunsite Scout rifle.) BML’s Accurate-Mag is also the proprietary manufacturer of magazines for the U.S. military’s XM2010 sniper rifle system.

The magazines are built from steel, heat-treated and coated with Teflon. On long-action box magazines, the feed-lip configuration allows the bolt to chamber the round closer to the centerline of the chamber. The feed lips also have a spring action that helps to spit the cartridge out from the magazine and into the chamber as the bolt is pushed forward into battery. This pantented system results in the fastest round-release time for a center-feed cartridge delivery system.

Accurate-Mag also manufactures bottom metal kits for short and long actions. The kits include a magazine and of 6061-T6 aluminum bottom metal that fit OEM rifles manufactured by Remington, Savage, and among others. These kits allow an internal magazine to be replaced with a high-capacity, detachable box magazine.

Multi-Caliber Chassis
Taking shape in Accurate-Mag’s CNC machines is the Multi-Caliber Rifle Chassis System, which was developed based on military requirements. The center section of this three-piece chassis system is built in short- and long-action configurations. The other two components of the chassis system are the buttstock and forend.

Since 1988 the U.S. military has fielded the M24 Sniper Weapon System, a version of the Remington Model 700 action chambered in 7.62x51mm NATO and mated to a McMillan A5 stock topped with a 10x42mm, fixed-power Leupold Ultra M3A optic. This is an excellent weapon, but as it has been fielded with more frequency, it has shown some limitations.

Military specs calls for the barrel to maintain 0.35-MOA accuracy for up to 10,000 rounds. Between training and in-field use, there are times when the rifle needs to be repaired, which requires the weapon to be pulled out of service and shipped to an armorer. But modular chassis systems can keep a weapon in the field indefinitely because they can be maintained in the field by the shooter. In September 2010, the U.S. Army awarded Remington a contract for the M24E1 Enhanced Sniper Rifle, which has since been renamed the XM2010.

The XM2010 differs from the M24 in a number of ways: The XM2010 is chambered for .300 Win Mag and has a detachable five-round magazine, a fully adjustable chassis to fit any user, a suppressor and a muzzle brake. But as much as the XM2010 has helped advance the sniper rifle, it still needs to be maintained by an armorer.

Accurate-Mag’s Multi-Caliber Rifle Chassis is designed for the next evolution of the XM2010. The system can be maintained by the shooter in the field with a minimum of downtime. The innovative inserts attach to a barreled action, like a Savage or Remington bolt action, allowing the user to change out a barreled action in mere minutes. Accurate-Mag refers to the resulting weapon as an “insert rifle.”

Insert rifles employ a dedicated action-block that is bolted to the action receiver and barrel. These action blocks are designed to fit like a glove on either a Savage, Remington or M14 action. Other action blocks for the .50 BMG, non-lethal weapons and high-tech weapons like user-guided grenades are in development. Each action block is unique to a manufacturer’s barreled action. What all action blocks share in common are trunnion tracks on the left and right side of the action block. These trunnion tracks mate to the trunnion pins in the chassis.

Vetting The System
On a cold day in January I traveled to an old, private club in Chappaqua, New York, to put the Multi-Caliber Rifle Chassis through its paces. Accurate-Mag 10-round magazines were loaded with .308, 175-grain Black Hills Match HPs with a factory velocity of 2,600 fps. The chassis held a Savage M10 action with an experimental 17.75-inch barrel.

The stock was completely ambidextrous with a length of pull that was adjustable from 13.5 to 15 inches. The cheekpiece had a 2-inch adjustment range and the buttstock can also be folded. (Some models can fold to the left side of the chassis or, in this case, to the right side, which secures the bolt handle.)

At a bench and using a Harris bipod, I centered the reticle of the 6.5-20x50mm Leupold Mark 4 ER/T dead on the target at 200 yards. Savage AccuTriggers are sweet, and I hit black with the first round. I did not zero the scope, nor was I able to test for muzzle velocity or accuracy, but the subsequent nine rounds clustered between 5 and 6 o’clock. Some bullets shared the hole of a previous bullet.

Then I tried a magazine in another .308 barreled action tuned by RW Snyder Gunsmithing. It was based on the Remington design, and again, 10 rounds, 10 holes. As before, I hadn’t adjusted the Leupold to my dope but kept shooting to a spot. This time I saw hits at 1 o’clock.

Even though it was cold enough to hear pond water freeze, I was pleased. I liked the V-shaped notch in the stock. With my non-shooting hand I was able to push the stock, using the V-shaped notch, into my shoulder while pushing forward on the pistol grip with my shooting hand to lock the rifle in place. I varied the pressure, and the groups on the target show that, but I’m sure with another box of ammo I could find the right balance. I ran an additional magazine through each action again and consistently hit a metal plate at 200 yards even though the tip of my nose was numb. Bang a gong—get it on.

Vin Battaglia, the principal and vice president of operations at BML, demonstrated how easily it is to swap out the barreled actions of the Multi-Caliber Rifle Chassis System. Vin pulled the bolt from the action and removed the scope. He then pressed the detent pin in the chassis with a bullet tip, pulled back on the pistol grip and removed the upper forend rail. Placing the rifle on its butt and pointing the muzzle skyward, he unscrewed the hand screw with a wrench, pivoted the Savage barreled action on the trunnion pins and pulled the action out of the chassis. He replaced it with a Savage M110 in .338 Norma Mag in the same chassis and reassembled the components, also adding a Gemtech suppressor. (It takes more time to describe how to swap barreled actions than it takes to actually do it.)

The .338 Norma’s ballistics are mighty different from those of the .308: The .338 Norma pushes a Sierra 300-grain BTHP with a muzzle velocity of 2,660 fps. I aimed for a spot, and Vin called the shot while looking through a Kowa spotting scope. I adjusted my aim, and the .338 Norma made the steel sing.

Back at the BML facility, Vin again swapped the action out of the chassis with an M14 barreled action. Within minutes, the rifle that was set up for long-range precision use now had an M14 insert setup for suppression fire. There is no need to check headspace or to make any mechanical checks to get the rifle on line. This does mean shooters will need an entire barreled action with an insert block at their disposal. But considering the amount of time a more traditional tactical weapon can be out of service (weeks or months) while it is being re-barreled by an armorer, the Accurate-Mag system’s ability to enable shooters to be back on line in minutes is a real boon. And when a shooters know the zero for their optic for different rounds, there will be no need to sight in the weapon again.

The Colt Competition M2012 rifle and Accurate-Mag’s’s new Special Service rifle employ Accurate-Mag’s high-tech Rifle Chassis System, which itself will be available to the commercial market in late 2013—the tactical rifle has evolved. For more information, visit accurate-mag.com or call 203-880-9485.