The Gunsmithing Story

The customer asked us to make a custom barrel chambered 300 Blackout for his Remington 700 action. He also wanted the new barrel to accept the same suppressor that he was using on his Thompson Center break action rifle. His goal was for this 700 bolt action and suppressor combination have the same performance as his Thompson Center and to be able to shoot the exact same reloads in both guns.

Using the barrel blank, we machined the front of the barrel to match the Thompson Center and threaded the back end to match the 700 action.

To begin recreating the front of the barrel, we measured the entire barrel and chamber of the Thompson Center. Then, to measure the twist rate (rifling) we took a fixed length brass cleaning rod and pushed it down the barrel. Using the length of the rod and how many times it turned, we calculated the twist rate.

After writing down all of the measurements and drawing a roadmap (similar to a blueprint) on a piece of paper, we began the machining process.

We started by threading the barrel to fit the Remington 700 action, timing it, and chambering it in 300 Blackout.

Then, we began the frontend duplication process. We contoured the barrel to fit the suppressor. This suppressor, instead of attaching to the end of the barrel, goes over top of the barrel enabling the user to have both quality sound suppression and a short overall length. Because of the suppressor’s design, the contour was relatively complicated with its various features. Luckily, we recently purchased a CNC lathe which makes machining complex profiles easier. Plus, it’s five horse power so it removes material way faster than my trusty old Southbend.

Finally, to finish duplicating the front end of the barrel, threaded it to fit the suppressor and milled ports into the barrel to allow the pressure to release into the silencer.

To complete all of the threading necessary to duplicate this new rifle barrel, we used our new chuck. But it’s not just any chuck—it’s the True Bore Alignment System from Straight Shot Gunsmithing. This chuck is designed by a gunsmith and built specifically for gunsmiths. It solves many of the problems with traditional chucks and allows gunsmiths to have the perfect concentric alignment necessary for thread jobs.

Problems with Traditional Chucks

There are several issues with using a traditional three or four jaw chuck for threading barrels. Especially when threading for suppressors, alignment is extremely important. The threads must be concentric to the bore or else the accuracy of the gun will be affected. On a thread job, the threads need to be perfectly concentric with the bore of the barrel—not the outside diameter of the barrel.

The three main problems are:

Inconsistent clamping force
Flexing material to achieve axial alignment
Time required to dial in the barrel

Three jaw chucks don’t have individually adjustable jaws—they both hold the material in place and adjust the alignment. Gunsmiths, therefore, can’t get the barrel perfectly true and so the barrel doesn’t spin concentrically.

While a four jaw chuck might be a little better and enable more adjustment, it’s still not perfectly true in both radial or axial alignments. On four jaw chucks, each individual jaw is adjustable which enables the gunsmith to spin the barrel radially true, but it doesn’t solve the problem of the barrel spinning out of axial alignment. That is, the gunsmith has no control over the back end of the barrel. This can cause the barrel to wobble resulting in threads which aren’t aligned parallel to the bore.

To put a band-aid on this problem, many gunsmiths use a spider—a mini four jaw chuck—on the other side of the headstock which enabled them to dial in the backend of the barrel. But, this causes the barrel to flex. Though it’s better, it’s still not perfect because the barrel will flex back once removed. Using this method, also takes an extremely long time to dial in because both jaws must be adjusted. So, it’s a lot of back and forth because each adjustment affects the other jaw.

Finally, in the case of a four jaw chuck, adjustment is also the clamping force. Thus with each adjustment, the clamping force differs. But, the clamping force must be overlooked in order to get the alignment right.

True Bore Alignment System Benefits

The True Bore Alignment System solves all of these problems and has three features which individually address each of the issues with traditional chucks. These features enable a gunsmith to make different adjustments on the barrel which are key to ensuring perfect threads.

Clamping Force

First, it has a six jaw chuck. This chuck is solely dedicated to clamping the barrel. Like a three jaw chuck, none of the jaws are adjustable so each jaw applies consistent force. But, with six jaws, it enables more accuracy. The six jaw chuck is then mounted and aligned to the True Bore Alignment System which has two individual parts which account for axial and radial alignment respectively.

Axial and radial Adjustments

The gunsmith first adjusts the axial alignment by pivoting this part into perfect axial alignment. After ensuring the bore spins perfectly parallel to the lathe, the radial alignment is adjusted to be perfectly true to the bore.

It’s safe to say that this was one of the best purchases our shop has made. Not only does it make our work more precise, but it also saves me an incredible amount of setup time. If you’re a gunsmith interested in purchasing this product, click here.

Next Up

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Threading with the True Bore Alignment System