Building a Custom Ruger American Rifle

When I reviewed the Ruger American Rifle, I mentioned that it was a “mixed bag” firearm that had “good bones”.  The good bones are the 3-lug action with reasonable bolt lift in a rifle that cost me less than $400.  I felt the accuracy potential of the rifle suffered from the manner in which the stock was constructed, but the potential was there.  When Modular Driven Technologies (MDT) introduced their ESS chassis system for the American, I knew there was great potential for a custom precision rifle.

So why build a custom rifle on a “cheap” rifle (I prefer inexpensive) like the American?  It is one of the few 3-lug actions I’m aware of at this price point and the twin V-block bedding system seems like it would work exceptionally well when integrated into a chassis system.  Couple that with the low cost and you have a winner.

My American was a Predator chambered in 6 Creedmoor.  I plan on making it into a custom 6.5mm rig, but not a 6.5 Creedmoor!  How about a 6.5×47 Lapua?  While the 6.5x47L isn’t as popular as the Creedmoor, it is a neat cartridge.  I’ve found it easier to load for and capable of extreme accuracy; plus, I already have brass and dies for it.  (for more about cartridge selection, see  Why not 308? The battle between 6.5 Creedmoor, 6.5×47 Lapua, 260 Rem, 243 Win, 6BR, 6×47 Lapua, and 6 Creedmoor)

There are a couple of downsides associated with the American, most notably that Ruger makes heavy use of MIM and plastic parts.  The bolt stop and firing pin cocking piece (above) are noticeable examples of this.   While they function fine, they do seem out of place on a custom rig.  The plastic bolt shroud is fairly cheap looking. I realize other manufacturers use them, the Tikka T3 for instance, but I can’t say that I am a fan (later changed in the T3X).

Before we get moving on our build, let’s take a few minutes to read the following disclaimer:

The contents of are produced for informational purposes only and should be performed by competent gunsmiths only. and its authors, do not assume any responsibility, directly or indirectly for the safety of the readers attempting to follow any instructions or perform any of the tasks shown, or the use or misuse of any information contained herein, on this website.

Any modifications made to a firearm should be made by a licensed gunsmith. Failure to do so may void warranties and result in an unsafe firearm and may cause injury or death.

Modifications to a firearm may result in personal injury or death, cause the firearm to not function properly, or malfunction, and cause the firearm to become unsafe.

I’ve also ordered the following from Brownells for this project:

Let’s begin by removing the barrel from a safe and empty rifle.

When you take a look at the Ruger American’s action, it looks like it isn’t round at first glance.  This isn’t the case.  The outside diameter is ~1.35″, the same as a Remington 700.  It does have two flats machined on the surfaces, but at the end of the day it is basically round.  This means a Remington 700 action wrench will fit on it, as shown above.  Since I don’t want the wrench to slip and rub the action, I coat the mating surfaces with rosin to prevent slipping.

Unfortunately, the barrel nut for the Ruger American is smooth.  It had an outside diameter of approximately 1.225″.  I didn’t have a wrench that would grab this.  I could have machined a wrench, but I decided to avoid the barrel nut all together and grab the barrel shank forward of the nut.  I held the barrel with a set of 1.175″ aluminum shims in a barrel vise.  Again, I coated the surfaces in rosin.

I posted the video below on my Facebook page to show how loose the fit is on the factory barrel to the action.  This is by far the loosest fit I’ve encountered on any rifle.  It is worth noting that the donor gun still shot well for the money!

“Breaking” the action off was fairly straight forward.  It was actually easier than any other factory rifle I had removed a factory barrel from to date.

With the barrel off you can get a better view of the action.  Most importantly, note how the flats cut into the side of the receiver limit the maximum diameter of the barrel you can install.  These flats limit your new barrel diameter to approximately 1.225″.

Here is a view of the barrel tenon and nut assembly.  This is a 1″x16 thread and the barrel doesn’t have a counterbore.

Further inspection of the barrel nut system shows some differences from other systems on the market, such as Savage.  Note the threads are a smaller diameter than the shank and the barrel nut has a recess in it to slide over the barrel shank.  This would give it a more finished appearance.

This is another look at the barrel nut.  Note the recess on the top edge.  This is what slides over the barrel tenon.

I’m going to be fitting a 6.5mm 1:8″ twist  Shilen Select Match barrel with a Remington Varmint contour on this rifle.  The shank on this tube is 1.249″.  You may recall the action flats won’t allow for a barrel above 1.225″ in diameter, so I went ahead and turned down the shank on the lathe.

With the shank turned down, I can get the barrel ready for the chambering process.  I cut 1″ off the end of the tube and secure it in a spider.  Sometimes I’ll use a four-jaw chuck or a Set-Tru 3-jaw; I’ve found all of the methods work.  I use a round range rod to dial in the bore.

I measured my action to determine the dimensions of the barrel tenon.   For this particular action the tenon will be .689″ long.  I begin by cutting the tenon to .998″ in diameter and .689″ long.  I also chamfer the end.

The tenon is coated with Dykem to make it easier to see the threads.

I get the lathe set up for threading.  I’m using a carbide insert, however, a high-speed steel insert tool would work just as well.  I make a light pass and check to make sure everything is set up correctly.

After the threads are cut, I use a high-speed steel 35 degree profile tool to clean up the shoulder of the barrel tenon.

At this point I can get set up to cut the chamber.  I use a variety of methods to hold reamers on the lathe.  In this case I hold the reamer in a Manson floating reamer holder. I coat the reamer with Do-Drill cutting oil and take light passes with a spindle speed of 70 RPM.  After I make a cut, I stop the lathe, back out the reamer, clean it, oil it and take another pass.

As the depth of the cut increases I can start checking headspace.  I leave a “go” gauge in the chamber and screw on the action with the bolt.  The gap between the front of the receiver and the rear of the barrel tenon is the depth that the chamber still needs to be cut.  I measure this with a feeler gauge and take a series of light passes.

When the action closes on the “go” gauge and stays open on the “no go” gauge, the chamber is cut to the proper depth.

Finally I break the inside edge of the chamber with a boring bar and some abrasive cloth.  If you don’t do this, rounds can hang up and brass will get scratched.

The muzzle on this gun will get a simple crown.  The barrel is dialed into the head stock the same way it was for the chamber end.  In this case I used a high-speed steel boring bar to make a recess at the end of the crown.  I think this looks pretty nice!  Alternatively, a form tool could have been used.

A quick pass on the belt grinder with a fine belt blends all of the surfaces.  I hold the barrel in a barrel spinner.  My left hand is used to keep the barrel from spinning too quickly from the grinder while the right hand moves the entire fixture back and fourth.

At this point the action can be installed on the barrel.  I use the same action wrench as before.  I am grabbing the barrel in a Farrell barrel vise.  The Farrel vise uses a set of aluminum V-blocks that doesn’t require shims.  It works well for applications like this.  To remove stuck factory barrels, the Brownells vise shown earlier is a better choice.

If you take a look at the embedded video from my Facebook page below, you’ll see the fit of the action to the barrel (first video) and how well the action fits into the stock (second video).

The barreled action is secured in the MDT ESS chassis and BOOM!

The rifle is finished off with a Timney trigger (excellent), Spuhr ISMS scope mount, MDT polymer magazine and Nightforce base with NXS F1 3-15×50 scope.

It looks great and shoots like a champ with Sierra 123 and 142 MatchKings!  The action is fast!  I’ll be posting more about it in another review.

To learn more about when Modular Driven Technologies (MDT) introduced their ESS chassis system for the American, click here!

Buy a Ruger American at Brownells!