Rebarreling a Winchester Model 70

Originally introduced in 1936, the Winchester Model 70 is an icon of the American rifle market. The two most notable features of the original Model 70 were it’s three position safety and non-rotating controlled round feed extractor. In 1964, Winchester redesigned the rifle and changed it from controlled to push feed. These newer Model 70s, known as “post-64” rifles, were produced until 2006. Frowned upon by the pre-64 Model 70 fans for its less refined construction and lack of controlled round feed, the post-64 Model 70s can serve the rifleman well.

My friend brought over his post-64 Model 70 243 Winchester rifle. The gun spent most of its life serving an across-the-course high power rifle shooter. The mix of the overbore 243 Winchester cartridge, years of competitive use, and high round count resulted in a shot out barrel. He didn’t have a new barrel blank, however, he did have an old factory take-off Remington 308 Varmint barrel to install. Taking a quick look at the barrel and action, it looked like the project would work, so we decided to give it a shot. REMchester anyone?

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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.

For use in this project, the following items were ordered from Brownells:

All lathe work is conducted on a Grizzly gunsmith’s lathe.

Before we can install a new barrel the old one needs to be removed. On this rifle, the threads were soaked in Kroil (a penetrating oil that is an essential item for gunsmithing) for a couple of days to make removal easier. The outside of the barrel is coated in rosin to prevent it from rotating in the barrel vise.

The Brownells barrel vise we’ll be using to remove the barrel from this action holds barrels with interchangeable aluminum bushings to match different barrel shank diameters.

The barrel is secured in the vise and an action wrench is used to unscrew the action. It is important to make sure the action wrench fits well against the action. In this case I am using the Brownells action wrench with the universal jaw. It grabs the flat bottom of the front of the Winchester action.

Note the tight fit of the bushing against the barrel.

The factory barrel tenon is measured to determine it’s length and headspace.

A quick check with the thread pitch gauge confirms the threads are 16 teeth per inch.

The action is also measured with a depth micrometer to check the barrel tenon dimensions. This serves as a check against the dimensions recorded from the factory barrel tenon.

The factory Remington barrel tenon (left) compared to the factory Winchester tenon (right). The Remington tenon is longer, has 1 1/16″-16 threads and a .150″ deep bolt nose recess on its face. The shorter Winchester tenon has 1″-16 threads and no counterbore.

Barrel tenon’s dimensions in hand, we can start fitting the barrel. The first step is to remove the old tenon. I like to use a cold saw. A cold saw is basically a miter box for steel, the one I have uses a special carbide blade. It makes short work of barrels, gives a fairly smooth finish, and does not induce heat into the part.

The barrel is mounted in the lathe. Since we only removed the threads from the barrel, the front part of the chamber is still in the barrel. A dial indicator is used to dial the barrel in on the lathe.

A facing cut is made across the breech end of the barrel with the high-speed steel 135-degree profile tool.

The tenon is cut to length and diameter. This cut was made with a 135-degree high-speed steel profile tool.

The tenon is coated in Dykem and the end chamfered.

Since I’m threading against the shoulder, I decided to use a lay down carbide threader (left), instead of the high-speed steel insert threader I normally use (right). Comparing the shapes, the carbide tool can cut closer to the shoulder.

While I normally prefer using the high-speed steel cutter, the carbide does work well.

A test fit shows the action can screw snugly against the barrel tenon.

The chamber is now cut with a Manson live pilot reamer. The reamer is fed with a MT3 blank held in the tailstock. This pusher set up allows the reamer to float in the bore and follow what remains of the factory chamber.

The headspace is initially checked with the go gauge and a depth micrometer.

As the headspace gets closer to the final dimensions, it can be measured with feeler gauges measuring the space between the bolt and action screwed onto the barrel with the go gauge in place.

A view of the tenon after the chamber has been cut to depth.

The bolt handle should close easily on go gauge, and stay open on the nogo gauge (above).

The last step is to cut a small radius on the end of the chamber to aid in feeding.

The barrel can now be installed on the action. For this task the barrel is secured in a barrel vise and the action wrench is used to torque the action on.

One last headspace check. For final inspection I use a .001″ match headspace gauge set. In this case, the bolt closes easily on the 1.630″ gauge (SAAMI minimum) and stays open on the 1.631″ gauge (.001″ over SAAMI minimum)- the rifle is chambered to minimum headspace.

The assembled rifle looks good pretty good. One day we will do something about the green paint on the barrel.

The real question is how does it shoot? When he headed to the range with the REMchester, the first few groups weren’t too shabby!165 grain Sierra GameKing over Varget, looks like a keeper!

A 200 yard ladder test with the 165 grain Sierra GameKing and H4895 showed promise as well (below).

The project came along better than we had expected. What a great way to give new life to a worn out rifle and keep a used barrel from ending up in the scrap bin.