Several American companies have offered switch-barrel rifles through the years, but none has come close to the commercial success of Thompson/Center. It all started in Rochester, New Hampshire, in 1967 with Warren Center’s Contender pistol. The action was eventually fitted with a buttstock and a longer barrel to give us the Contender Carbine. In 1983 a totally new single-shot rifle called the TCR 83 was introduced, and it was later improved a bit and renamed the TCR 87. The Encore came along in 1996.
Continuing T/C’s switch-barrel tradition is the bolt-action Dimension. Far more than a run-of-the-mill switch-barrel design, its Locking Optimized Components concept makes it virtually a switch-everything rifle.
Barrels of various calibers can be interchanged, but so can the appropriate bolts and magazines for them. The system is chock full of excellent details that make the system easy to use. For example, all bolts and screws that are loosened during a switch are of captive design, which means they won’t mysteriously disappear as gun parts are prone to do. Tools required for going from one caliber to another come with the rifle.
The stock is designed to be used with different families of component packages, with each part within a specific group identified by a letter of the alphabet. For example, barrels in .223 Remington and .204 Ruger are permanently marked “A,” as are the bolt, magazine and magazine housing that are compatible with them. The other components families are “B” (.243 Win., 7mm-08 and .308), “C” (.270 Win. and .30-06) and “D” (7mm Rem. Mag. and .300 Win. Mag.). The .22-250 requires its own magazine but uses a “B” housing. To prevent an incorrect parts combination, the bolt from one family will not work with a barrel from another family.
The blued chrome-moly barrels fit both right- and left-hand receivers and are 22 inches long for standard calibers and 24 inches for magnums, all with five-groove rifling. Bolt length is the same for all cartridges, but bolt travel is modified for cartridges of various lengths by machining the bolt-stop groove in the body of the bolts to different lengths—short (.223), medium (.308), a bit longer (.30-06) and longer still (.300 Magnum). The counterbored head of the bolt contains a spring-loaded extractor and a plunger-style ejector. A cocked firing pin is indicated by protrusion of the cocking piece from the rear of the bolt shroud.
The fluted body of the bolt is the same diameter as the locking lugs. The use of three lugs reduces bolt rotation to about 60 degrees, allowing a scope to be mounted quite low. It also increases the cocking cam surface angle, which requires a bit more effort to rotate the bolt compared with a two-lug design. The long handle with its large knob—along with an occasional dab of lubricant to the cocking cam surface—goes a long way toward making the bolt of the Dimension easy enough to operate.
The bolt is removed by first retracting it to the rear, then, while depressing the release located on the side of the receiver, rotating it clockwise until its handle touches the side of the stock, at which point it is free to be retracted completely from the receiver. When removing and installing the bolt, you will eventually scratch the comb of the stock with the sharp edge of the bolt shroud, at which point you will thank T/C for going synthetic rather than French walnut.
An AR Influence
Utilizing the AR-15 method of attaching the barrel allows ounces to be trimmed away by using an extremely light receiver machined from Type 7075 aluminum. The barrel is screwed into a 13/4-inch-long steel extension, which slides into the front of the receiver. The barrel is indexed to its proper position when a steel pin at the bottom of the extension engages a notch in the face of the receiver. Turning a nut—or torque collar, as T/C calls it—onto the threads of the receiver holds the barrel in place. Closing and rotating the bolt engages its locking lugs with shoulders machined into the interior surface of the barrel extension.
A conventional recoil lug is replaced by a better idea. A wide slot machined through the bottom of the receiver ring exposes a V-shaped surface machined into the bottom of the barrel extension. It mates with a steel lug of the same shape rising up from the floor of the stock, and the two are drawn tightly together when the front action bolt is tightened. In addition to resisting recoil, the “V-within-a-V” fit orients a barrel precisely the same each time it is removed and then reinstalled.
This, along with using the supplied tool to apply the prescribed amount of torque to the action bolts when installing the barreled action into the stock, ensures a return to zero when barrels are switched, and it also resists rotational force applied to the receiver each time the rifle is fired. The tang of the receiver rests atop an aluminum pillar embedded in the stock.
The fire-control system is the same as on the T/C Icon, and the bolt can be rotated with the two-position safety engaged. Trigger pull weight is user-adjustable within a range of 31/2 to five pounds.
The detachable, single-column magazines of all calibers hold three rounds that feed into the chamber as smoothly as greased pigs. Pressing a latch at the front of the magazine allows it to drop freely from the rifle of its own weight. The exposed latch with its light-tension spring is one detail I’d like to see improved. A bump while moving through brush or banging the rifle against the frame of a backpack could result in a lost magazine.
The Dimension comes with a two-piece, Weaver-style base attached to its receiver. Since points of impact will differ for barrels of different calibers, a scope with accurate repeatability of adjustments will make life easy. You simply zero the scope for one of the barrels and then record windage and elevation corrections that have to be made when the other barrel is installed. Another possibility is to have one scope zeroed for the .308 deer barrel and a scope of higher magnification zeroed for the .223 coyote barrel. Although the Weaver-style mount is renowned for its ability to return a scope quite close to zero when it is removed and reinstalled, a few confirming shots on paper before heading to the hunting grounds are still a good idea.
Available at extra cost is a bridge-style mounting base, the front of which clamps securely to slotted dovetail cuts in the top of the barrel. Its rear end is vertically split into two parts, one of which attaches to the receiver. To use it, the two-piece base that came attached to the rifle is removed, and screws from the rear section are used to attach the rear base of the bridge-style mount to the receiver. After it is installed, a large bolt draws the two halves together.
Attaching a scope to each barrel is convenient, but this system does position a scope much higher off the rifle than the standard base. Because the receiver wall is quite thin, there are not many threads in two holes drilled and tapped for the bases, so regardless of which mounting system is chosen, the screws should be coated with liquid thread lock prior to installation. Otherwise they will quickly vibrate loose.
Pulling a Switch
With how the Dimension works behind us, let’s first remove the bolt and magazine, then move on to switching barrels. If the rifle has the bridge-style scope mount, the rear bolt is turned out until its half of the base is loose. Next use the torque tool to break loose the front and rear action bolts, then switch to the other wrench for turning them out far enough to free the barreled action for removal from the stock. After attaching the V-block wrench through the bottom of the receiver and into the barrel shank, insert the shaft of the torque wrench into the hole of the V-block marked “L” (for “loosen”) while engaging the teeth of its gear with those on the barrel nut. Insert the torque wrench so its handle and the handle of the other tool can be squeezed together like pliers. With the barrel nut loose, remove the two tools and screw it all the way off the receiver. The barrel is now free to be removed.
After inserting another barrel, hand-tighten the barrel nut, then install the two tools, but this time insert the shaft of the torque wrench into the hole of the V-block marked “T” (for “tighten”). Squeeze the handles together until the handle of the torque wrench slips with a loud click, indicating that the correct amount of torque has been applied to the barrel nut.
If a switch is being made from one family of cartridges to another, now’s the time to swap magazine housings in the stock. When installing the stock, use the torque wrench to first tighten its front bolt all the way, then move to the rear bolt. If the barrel is wearing a bridge-type mount, its rear bolt is tightened last. Be sure and tighten all three until the torque wrench slips with a loud click. Insert a magazine and bolt for the cartridge you have switched to and the rifle is ready to go.
Form Meets Function
The entire surface of the stock feels a bit tacky in the hands, and that along with soft rubber panels at the sides of the wrist and forearm offers a no-slip grip, even during a rainstorm. Posts fore and aft for quick-detach sling swivels are there, and length of pull is 13⅜ inches; two removable spacers beneath a very cushiony one-inch-thick recoil pad allow pull length to be reduced to 12⅞ and 12⅜ inches.
The stock is designed to be used with varmint-weight barrels of heavy contour, which are in the works, and sizing the channel in the stock to fit them leaves a big gap all around a standard-contour barrel.
A couple of strips of black electrical tape will prevent the entry of rain, snow and woods debris, and the deer, elk and prairie dogs that get shot with the rifle will never know. Total weight with a .308 barrel is 7¼ pounds, and a longer magnum barrel adds a couple of ounces. A light scope, a carrying sling and a loaded magazine bring the hunt-ready heft to about 8¾ pounds.
I had three barrels but only two bridge mounts, so I accuracy-tested the .308 Winchester barrel with the rifle wearing the Weaver two-piece mount and attached the bridge mounts to the .223 Remington and .300 Winchester Magnum barrels. I then zeroed those two barrels three inches high at 100 yards. I fired five three-shot groups with one, then switched to another and continued switching until I had shot each with three different loads. I did so to prove to myself that each barrel would return to zero, and that’s exactly what happened. No stopwatch was handy, but I’m sure I was doing a barrel switch in less than a minute toward the end.
I must be honest: The exact opposite of “pretty” was the first word that came to mind when I got my first look at the buttstock with its rainbow-shaped comb and belly. After I had fired a few rounds, the stock felt so darned comfortable I have now forgotten what there was about it that I didn’t like.
There were no feeding issues with either of the three cartridges, even when the rifle was used as a single-shot as I usually do when shooting prairie dogs. Just toss a cartridge through the loading port, close the bolt and shoot. The trigger had a tiny bit of creep and broke at a four-pound average with a variation of three ounces between pulls. It was so nice and crisp that I didn’t bother to reduce its weight.
What we have here is an extremely versatile rifle that’s fun to shoot and interesting to boot. During winter it’s just the ticket for big-game hunting. Come spring, a barrel switch transforms it into a varmint rifle. Its length-adjustable stock along with interchangeable barrels in calibers generating various levels of recoil make it a rifle that can be used by the whole family.
The Dimension’s hunt-ready weight with a scope, sling and loaded magazine runs around 8¾ pounds.
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