Building a Custom 308 Precision Chassis Rifle – PART 2- Barrel preparation and threading

This is the second post in a three-post series about building a Custom 308 Precision Chassis Rifle, the first post, can be found here: Building a Custom 308 Precision Chassis Rifle- PART 1

In part one of this series, we started converting our Remington 700 SPS into a custom rig. We stripped the action and trued it as well as the bolt face. In this post, we’ll finish it up.

Before we get to the work, please take a look at the following disclaimer:

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I ordered the following tools and parts from Brownells to complete this project:

In addition to these parts, for this build I selected a MDT ESS chassis system. The MDT ESS chassis system offers a series of advantages over a fiberglass stock. It is readily adjustable to fit a wider range of shooters and optics and in this configuration it comes with a continuous top rail for use of additional equipment; and most importantly, the ESS chassis is easy to install.

Since we are going to do a lot of barrel work, we need to use a lathe- not really a way around it when you are building off of a rifle blank. This is my lathe (when it was new, it is way filthier now). It is a Precision Matthews PM-1440GT. I’ve found it to do everything I could ask of it exceptionally well.

As a reminder, this is where we are starting this post, trued action in hand. Time to take some measurements so I can start work on the barrel.

I’m using a stainless-steel Shilen #7 Select Match barrel blank with a 1:10″ twist.

I like to cut off the last 1″ or so of the barrel on a bandsaw before I bring it over to the lathe. When i get to the lathe I mount it with a four-jaw chuck with the muzzle hanging out the opposite side of the headstock and supported by a spider. I first “dial” the barrel in concentric to the spindle on the outside diameter and face the breech end.

Once this is done, I insert a “range rod” which is a custom ground hardened steel rod that fits the bore. I then use a dial indicator to dial in the barrel off the axis of the bore. This is important since the bore of a barrel is seldom perfectly centered in the barrel.

Now I cut the tenon to the length and diameter I need. I like to fit the tenon to the lug I am using. I normally make this cut with a 35 degree high-speed steel profile tool and proceed slowly.

When the recoil lug fits over with a slight drag, you know you have a good fit! Note the chamfer I cut on the back end of the taper. This makes installing a tight fitting recoil lug easier, I also find it makes for a better finished product after the threads are cut.

I coat the tenon in some Dykem. Then, I move over from the shoulder and cut a groove in the tenon. This separates the tenon into two sections, the unthreaded section that supports the recoil lug and the threaded section that screws into the action.

Another look at the tenon, this time with the recoil lug in place. I manufacture the lug shown in the image. It is cut from 17-4 900H steel and then double disk ground.

With the tenon cut to spec, it is time to start working on the threads. In this case I am using a laydown style threading tool. I like to make a light scratch pass first to check the pitch with a thread gauge. If a mistake was made in the setup of the lathe, now is the time to figure it out.

I take my time and always cut my threads slowly. I like to fit them precisely to the action. Once everything fits nicely, I can move onto cutting the counterbore. I’ll pick up with the cutting the counterbore in PART-3 of this series!