Thompson/Center Arms Dimension Rifle Review

Part 5 - Internal Features

December 1, 2012

Thompson/Center Dimension Rifle Review

So far, I have covered most of the external and operational features of the Thompson/Center Dimension Rifle.  This part of the review will focus on features that I would consider internal in nature.  I have also tried to provide many photos so that you can study them and form your own opinions on what you see.

 


Receiver Assembly

I show the receiver assembly with the trigger assembly still attached, but in reality removing the trigger assembly is simple and I have shown it removed further below.  The receiver is made from 7075-T6 aluminum alloy and comes with a black anodized finish.  The rear stock mount bolt hole has a threaded steel insert to prevent from wearing out the threads in the aluminum alloy.  The Weaver-style mounts are also made from some type of aluminum alloy.  I'm not sure of the type, but any alloy would be sufficient for this purpose.

Figure 1
Thompson/Center Dimension Rifle Review

Figure 2
Thompson/Center Dimension Rifle Review

The forward lower side of the receiver has a notch in it to allow the lower V surface of the barrel extension to nest in the V block mounted in the stock and allow the forward stock bolt to thread directly into the barrel.  You can also see that the scope mount holes are fully threaded into the top of the receiver.  Since this is an aluminum receiver, you need to be careful not to over torque these screws and strip the threads in the aluminum receiver.

Figure 3
Thompson/Center Dimension Rifle Review

Figure 4
Thompson/Center Dimension Rifle Review

This next photo gives you a good look at the forward lower side of the receiver.  The U notch in the threaded area for the barrel nut is what mates with the pin on the barrel extension to ensure consistent alignment of the barrel and receiver.  There is a very small amount of play (looseness) in this fit, so I recommend always making sure the play is fully to one side each time you torque the barrel nut.  Since you tighten the barrel nut by turning it clockwise, I also recommend that you rotate the barrel in the clockwise direction when trying to get all the looseness to one side.  This way, as you tighten the barrel nut, doing so would not rotate the barrel.

Figure 5
Thompson/Center Dimension Rifle Review

Every time I look at the pin that holds the bolt stop lever in place, I think the pin has backed out too much to be correct.  When installed to it's full depth, the pin sticks out of the receiver by the amount shown in these photos.

Figure 6
Thompson/Center Dimension Rifle Review

One area that I have immediately started to see some wear is on the edges of the receiver where the bolt installs in the rear of the receiver.  Since the edges form a sharp corner, the steel bolt will have a tendency to wear the surface finish off the bolt unless you are extremely careful each time you remove and install your bolt.

Figure 7
Thompson/Center Dimension Rifle Review

In this photo below you can also see where the bolt handle touches the receiver and has worn some of the anodized finish.  I don't feel this is a show stopper by any means, but it is something you should expect to see over time.

Figure 8
Thompson/Center Dimension Rifle Review

Based on the geometry of the part, most likely the receivers are machine from a round billet of aluminum.

Figure 9                                                               Figure 10
Thompson/Center Dimension Rifle Review   Thompson/Center Dimension Rifle Review


Trigger

The Dimension rifle comes with an adjustable trigger assembly which has a two position safety.  The two photos below show the safety in the "safe" position (left) and "fire" position (right).

Figure 11                                                             Figure 12
Thompson/Center Dimension Rifle Review   Thompson/Center Dimension Rifle Review

There is a round window on the left side of the trigger assembly that allows you to see the sear engagement.

Figure 13
Thompson/Center Dimension Rifle Review

The trigger comes with the standard tamper proof coatings to prevent you from changing sear engagement and over travel.  The front of the trigger also comes with ridges to give your finger a textured surface.

Figure 14                                                          Figure 15           
Thompson/Center Dimension Rifle Review   Thompson/Center Dimension Rifle Review

Removing the trigger assembly was extremely easy and can be done by just pushing out the two pins with a small punch.  Actually I was able to push these pins out with a paper clip.  At the lower side of the safety selector, you can see a cone tip spring loaded button that provides the force against the safety to make the safety want to stay in either the safe for fire position.

Figure 16
Thompson/Center Dimension Rifle Review

On the top of the trigger assembly is the adjustment screw which allows you to adjust the trigger from 3.5 to 5 pounds.  For this rifle, the lightest trigger adjustment possible was 4 pounds.

Figure 17
Thompson/Center Dimension Rifle Review


Frame Assembly with Trigger Assembly Removed

Since I removed the trigger assembly, I decided to show some more photos of the receiver.  T/C calls this receiver their "universal receiver" because this same receiver is used to accept small, medium and long action calibers.

Figure 18
Thompson/Center Dimension Rifle Review

Figure 19
Thompson/Center Dimension Rifle Review

Figure 20
Thompson/Center Dimension Rifle Review


Bolt Assembly

The bolt assembly is made from steel and has a blued finish.  The bolt stop lever rides in the groove on the left side of the bolt which is used to maintain the open position of the bolt as you pull the bolt rearward.  The length of this groove varies based on the caliber being used (small, medium or large action).  For example, the distance from the front of the bolt to the end of the slot is 1.80" on the "B" series bolt.  This same distance measures 2.25" on the "A" series bolt.

Figure 21
Thompson/Center Dimension Rifle Review

The body of the bolt is fluted which adds to the look of the rifle as well as helping to reduce weight.  The bolt handle has a slightly oversized feel which I think allows for firm gripping and quick cycling.

Figure 22
Thompson/Center Dimension Rifle Review

The bottom of the bolt has a machined flat surface which appears to be another weight reduction feature along with providing for a flat surface for marking the caliber series for the bolt.  The bolt shown is marked with "B" and is used for my .308 Win configuration rifle.

Figure 23
Thompson/Center Dimension Rifle Review

The bolt has a three locking lug design along with a fairly standard plunger ejector and extractor.  Also, down the body of the bolt is a slot which will help to vent gasses in the event of some type of case rupture.

Figure 26
Thompson/Center Dimension Rifle Review


Barrel Assembly

The barrel has an extension similar to AR style rifles.  It is this extension that provides the locking lugs on the barrel along with setting the correct head space when used in conjunction with the bolt.

Figure 25
Thompson/Center Dimension Rifle Review

I believe this barrel extension lies at the heart of the Dimension rifle when it comes to producing consistent shots when you swap barrels.  The barrel extension has a lip that indexes the depth of the barrel into the receiver and also acts as the bearing surface for the force applied by the barrel nut.

Figure 26 - Top
Thompson/Center Dimension Rifle Review

The barrel extension comes with a vent hole on both the right and left side.  Since the receiver has a hole on the right or left, depending on wether you purchase a right handed or left handed rifle,  the barrel extension having a vent hole on both sides is proof that the barrel assemblies are designed to function as either a right or left handed rifle.

Figure 27 - Left
Thompson/Center Dimension Rifle Review.

The bottom of the barrel extension has an alignment pin used to index the correct rotational position of the barrel in the receiver.  The bottom of the barrel extension also has two machined flat surfaces that form a V shape.  In between these two surfaces is the forward stock bolt attachment hole.

Figure 28 - Bottom
Thompson/Center Dimension Rifle Review

Figure 29 - Right
Thompson/Center Dimension Rifle Review

My speculation is that the "2" shown on the barrel extension represents that this extension will work for the "B" series calibers, yet the extension is not truly caliber specific within the series.  I feel fairly confident that this is the case because the barrel extension on my .223 Rem barrel is marked with a "1".  The barrel extension also has a feed ramp and I would say that the rounds feed very nicely into the chamber from the magazine.

Figure 30
Thompson/Center Dimension Rifle Review


Barrel Nut

The barrel nut is made from steel and the geometry of this part makes me think it is a forged part.  The outside of the nut has 60 gear teeth used for tightening the nut.  The torque applied by the barrel nut to hold the barrel in place is about twice that applied by the Torque Tool due to the differences in diameter of the barrel nut versus the torque tool gear.  This means the barrel nut is tightened to about 110 in-lbs of torque.

Figure 31
Thompson/Center Dimension Rifle Review

Figure 32                                Figure 33                               Figure 34
Thompson/Center Dimension Rifle Review   Thompson/Center Dimension Rifle Review   Thompson/Center Dimension Rifle Review


Stock

The stock is made from a rigid polymer material and "features ARMORSOFT® coating, which adds durability and noise reduction when hunting in dense vegetation".   The thing I liked most about this coating is that it gives the stock a slight rubbery feel.  The stock also comes with two gray areas (forend and pistol grip) which are molded rubber ribbed areas that do add a considerable amount of gripping texture to the stock.

Figure 35
Thompson/Center Dimension Rifle Review

Figure 36
Thompson/Center Dimension Rifle Review

Figure 37
Thompson/Center Dimension Rifle Review

The receiver and barrel are mounted to the stock with two screws.  The forward screw attaches directly to the barrel extension inside the receiver.  The V surface on the barrel extension mates up with the V block molded into the forward end of the stock.  The V block in the stock appears to be made from steel (magnetic) and is integrally molded into the stock.

Figure 38
Thompson/Center Dimension Rifle Review

Figure 39
Thompson/Center Dimension Rifle Review

At the rear of the stock attachment area is an aluminum pillar that is molded into the stock.  I feel the steel V block and aluminum pillar provide good support to the barrel and receiver and should provide for consistent accuracy.  The forward stock screw is held in place by a rubber O-ring.  The rear stock screw is held in place by a star shaped retainer that is pressed in the screw hole in the bottom of the stock.

     Figure 40                                                          Figure 41
Thompson/Center Dimension Rifle Review   Thompson/Center Dimension Rifle Review


Buttpad & Shims

Even though the spacers look similar in shape, there are some contour differences.  If you were to shorten your length of pull by 1/2", I believe T/C intended for you to remove the black spacer.  The spacers are made from a hard polymer material.  The buttpad has a hard polymer material core and is then surrounded by soft ventilated rubber.  Having already shot this rifle, I can say first hand that the recoil pad does a good job of reducing felt recoil.

Figure 42
Thompson/Center Dimension Rifle Review


Magazine Adapter

The magazine adapter is an all polymer part (probably glass filled nylon) and comes marked with the part number and caliber series (in this case B).  When the rifle is assembled, the adapter is held tightly in place with no rattle.  The front of the adapter is cutout so that the magazine catch engages against the stock and not the adapter.

Figure 43
Thompson/Center Dimension Rifle Review

Figure 44
Thompson/Center Dimension Rifle Review

Figure 45
Thompson/Center Dimension Rifle Review

Figure 46
Thompson/Center Dimension Rifle Review

 

Thoughts

I liked the Dimension Rifle's pillar system for mounting the receiver/barrel assembly to the stock.  The more I study this rifle, the more it makes me think of a bolt action version of an AR style rifle.  If this rifle continues to be a popular platform, I would expect to see tactical variants in the future.  Even though the thought of changing calibers by taking the rifle apart and reassembling it may seem complicated, T/C had done a good job of keeping it simple.

For more detailed photos and commentary, make sure you check out the other parts of this review and feel free to leave comments on my Reader's Comments page.  The following links are provided to help you see other parts of this review. 


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