The 7.62×39 mm Russian cartridge has a strong following in the United States. While most shooters encounter it in the SKS or AK47, it is also available in more refined rifles like the Ruger Mini-30, Model 77, or CZ 527. Unfortunately for the M700 shooters among us, Remington never offered a 700 chambered in it. Well, I always wanted one chambered in 7.62×39 mm (I have a couple cases of ammo left over from when I owned an AK), so I decided to build one.
The 7.62x39mm Russian requires a .4545″ bolt face. This is commonly referred to as a PPC bolt face. (It should be noted that the 6mm PPC uses the 220 Russian as a parent case, which in turn uses the 7.62×39 mm Russian as its parent case! Perhaps we should refer to it as a 7.62×39 bolt face?) Remington 700 bolts are most commonly encountered in 223 (.3991″), 308 (.4861″), and magnum (.5471″) bolt face sizes. This leaves a the rifle builder with a few options; buy an aftermarket bolt with the right bolt face, try to use a standard bolt face and see if it ejects (some PPC guys report decent results with this), or modify the bolt face of an existing rifle to the correct size. I’ve had mixed results with the aftermarket bolts I’ve purchased from PTG, so I passed on that option. Initial testing with the 7.62×39 mm Russian on a standard Remington bolt face showed ejection was a problem, so that was out. That left the final option, bushing the bolt face to the proper size and installing a Sako extractor- which is what I elected to do for this build.
Selecting the barrel was a bit of a chore. Due to its widespread proliferation and popularity, reaching consensus on 7.62×39 specifications can be difficult. Ammunition and firearms for it are manufactured all over the world. For instance, for shooters in the United States, bullets in .308″ and .310″ diameter are often encountered. The Sporting Arms and Ammunition Manufactures’ Institute (SAAMI), which governs voluntary industry standards for the shooting industry in the US, suggests a groove diameter of .310″ and bullet diameter of .310″ (-.002″). This means both the .310″ and .308″ diameter bullets will be within specification and can be used.
Anticipating what ammunition will be used, seems like the prudent choice before selecting a barrel. Since I plan on mostly shooting Russian steel case ammunition with .310″ bullets, that helped guide my decision. Rather than use a match grade, .308″ groove barrel, I decided to order a Green Mountain chrome moly barrel. The barrel has a .300″ bore, .310″ groove, 1:9.5 twist barrel blanks. Had I planned on loading Lapua brass with Sierra bullets, I would have selected a different barrel.
The rifle was built with the following parts from Brownells:
- Green Mountain barrel blank, .310 bore
- Remington 700 short action receiver
- Modular Driven Technologues (MDT) HS3 chassis system
- MDT AICS style magazine
- MAGPUL PRS stock
- Timney 517 trigger
- Harris bipod
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The work will start with modifying the bolt face to work with a PPC sized cartridge. I’ll be modifying a factory Remington bolt that came with a .223 Remington bolt face. The bolt is secured in a LaBounty fixture.
The bolt is dialed-in on the lathe. Factory Remington bolts are made from three pieces, a bolt head, bolt body and handle. I prefer to indicate off of the bolt head, if you look carefully at the bolt you can see where the body and head join one and other.
A boring bar is used to machine off the rim and widen the bolt face. I normally open this cut up to approximately .625″.
A bushing made of scrap barrel steel fits inside this cut. I turn these bushings in advance. The bushing will be soldered in place and turned to the correct size.
The bolt is removed from the lathe. As shown in the photo above, the bushing will block the ejector plunger hole.
By notching the bushing, the ejector path is cleared. I did this on a milling machine with a 1/4″ four flute end mill, however, a file or rotary tool would work as well.
Since the soldering process introduces heat to the bolt, the hardened surfaces of the bolt lugs need to be protected. I use Brownells Heat Stop, heat control paste for this.
I like to use Hi-Force 44 solder for this task. It flows at a relatively low temperature, 475F. I like to use a portable MAPP torch to heat the area.
The bolt after the bushing is soldered in place.
The bolt is placed back into the lathe and dialed in. The new bolt face is machined with a high-speed steel boring bar.
The bolt face is now the correct size. Time to install a new Sako extractor.
The bolt is secured in a Sako machining fixture on the milling machine. The centerline and front edge of the bolt are located.
An end mill is used to cut the pocket for the extractor.
A .120″ hole is drill through to the center of the bolt. This retains the extractor in place.
Now is a good time to test fit the extractor to ensure everything lines up.
The bolt is mounted vertically and a hole is drilled for the extractor spring.
The blank is 1.375″ in diameter and 24″ long. Quite a heavy and impressive piece of steel.
The blank is mounted in a four jaw chuck and indicated to the bore.
The barrel is now mounted between centers. I am looking for a finished barrel length of 16″ long, so I will be profiling 17″ of the blank. Since I will be using the rest of the barrel for a barrel length and velocity experiment, this excess material is passed through the headstock. The live center in the tailstock supports the chamber end of the blank.
I don’t work on chrome moly barrel as much as I work on stainless. As any machinist will tell you, speeds and feeds are key when machining. On this pass, I was experimenting with spindle speed. On the left the spindle speed was 220 RPM, on the right 360 RPM, all other settings were the same. Note the superior finish on the right side of the cut.
A factory Remington Varmint contour barrel has a slight taper on the tube. It measures .950″ in front of the shank, and .850″ at 26″. In this case, I’ll be cutting a modified Rem Varmint taper and the entire barrel forward of the shank, .950″. I like to take a heavy pass, .040-.050″ at a time. Since I don’t have a lot of distance between centers, I didn’t need a steady or follow rest to get decent results. I’m cutting from left to right, towards the tail stock. Cutting in the opposite direction could cause the barrel to slide into the headstock.
All the turning makes for an impressive pile of shavings!
To determine the dimensions for the shank, I measure a barrel that I’d like to copy. This is a Bartlein with a Rem Varmint profile from another project. I mark the barrel in .100″ increments forward for the straight shank. I then record the measurements.
The measurements allow me to formulate a cut list needed to duplicate the profile. In this case, the list shows how far in I need to cut from the outside diameter of the blank. The number in the left column indicates how far from the shank I need to stop the cut. For instance, 1.5 indicates I need to take a cut .088″ deeper than the shank and stop 1.500″ from the beginning of the shank.
This is what the barrel looks like after the series of step cuts.
Another view of the step cuts. The black line indicates the end of the straight part of the shank.
A lathe file allows me to smooth out the profile.
This is the muzzle section of the barrel that was held in the chuck when the profile was turned. As stated earlier, I’d normally just chop it off, but I want to get some barrel length and velocity data with it. Before leaving the lathe, I’ll turn it down closer to the finished diameter of the barrel.
The barrel when it leaves the lathe.
The barrel is mounted in a barrel spinner. The barrel spinner supports the barrel between two ball bearings with a set of nylon centers. You can make or buy a barrel spinner, this one is a Clymer I ordered from Brownells.
My left hand is used to slow down the rotation of the barrel as it is held in the center.
The finish barrel barrel looks pretty sharp. A big change from when we started.
The action and bolt are measured to determine the headspace and barrel tenon dimensions.
The barrel is secured in the lathe and dialed in so the bore is concentric with the lathe.
The tenon is cut to accept the recoil lug.
The tenon is coated in Dykem. A groove is cut to seperate the area that will support the recoil lug and threads. The threads will be cut with a carbide insert tool.
The carbide tool does a great job on the barrel threads.
The action and recoil lug are test fit on the tenon.
The bolt nose recess is cut with a high-speed steel boring bar on the lathe. This will accept the bolt nose.
Test fitting the lug, action and bolt.
A PTG adjustable reamer stop is mounted to a Manson solid pilot reamer.
A view of the chambering set up. A MT3 blank is used to push the reamer into the chamber. Using a flat faced blank allows the reamer to float and follow the barrels bore.
When the bolt closes on the go gauge…
And stays open on the NOGO, the chamber has been cut to the proper depth.
After the chamber is cut to the depth, the outside edge of the recess and chamber are broken to aide in feeding.
To begin work on the crown and muzzle brake, the opposite end of the barrel is dialed in on the lathe.
A tenon is cut for the Badger FTE brake that will be installed.
Threads are cut 5/8″-24.
The brake is test fitted to the barrel. At this point the muzzle brake installation process is complete.
The barrel is secured in a barrel vise and an action wrench is used to tighten it in place. This is a good time to confirm headspace is correct. The bolt should close on the go gauge, and stay open on nogo.
This rifle will also be equipped with an oversized tactical bolt knob.
The bolt is secured in a fixture on the lathe. The fixture I am using here is made by PTG.
The handle is aligned by eye, I’ve never had luck measuring here. A center drill is used to drill a hole for the lathe’s live center.
The bolt handle is removed. I cut towards the tail stock- this is important. The bolt handles on factory Remington bolts are soldered to the bolt body. If you put too much stress on the handle it can snap off. By cutting towards the tail stock, less pressure is put on the handle.
The tenon is turned until it is .313″ in diameter.
A 5/16-24 die is secured in a floating die holder.
As the lathe is run the die advances up the tenon cutting the threads.
A high-speed steel 35 degree profile tool is used to clean with the tenon’s shoulder.
The handle fits well. This is a Badger Ordnance miniature tactical bolt handle.
I painted the barreled action USMC Red. I don’t know if I love the color, but it has a great name! Back into the curing oven.
After a couple hours in the oven I can check my work. This thing is really red! A red rifle for a red cartridge!
I left the rest of the parts black for a contrast- I may be painting a conservative color….
Build parts are:
- Remington 700 short action receiver
- Green mountain .310 groove 30 caliber blank turned to sporter contour
- Timney 517 trigger
- MDT HS3 chassis
- MAGPUL PRS stock
- Spuhr mount
- Nightforce NXS 5.5-22×56 mil/mil scope
- Badger FTE brake
- Badger mini tactical knob
The gun feeds and extracts well. Ejection has been a problem with some cases failing to clear the ejection port. I changed the spring on the ejector and the increase tension helped, however, it still requires a little bit of tuning.
This is the best group I was able to fire with steel cased ammunition, 5-shots Brown Bear 123 grain JHP, .918″ (.877MOA).
Between the weight of the rifle, small cartridge and brake, the gun barely moves when you shoot it. I’m in the process of acquiring better ammunition to test with.
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