Building a Remington 700 in 7.62×39 mm Russian

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:

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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.

223 donor bolt Rem 700 7.62x39

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.

dialing in bolt for SAKo Rem 700 7.62x39

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.

machined out bolt nose 2 Rem 700 7.62x39

A boring bar is used to machine off the rim and widen the bolt face.  I normally open this cut up to approximately .625″.

bushing fit in bolt Rem 700 7.62x39

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.

bushing blocks ejector Rem 700 7.62x39

The bolt is removed from the lathe.  As shown in the photo above, the bushing will block the ejector plunger hole.

machined bushing

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.

heat control paste Rem 700 7.62x39

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.

silver solder set up Rem 700 7.62x39

The heat control paste is packed around the lugs.  Comet flux is applied to the bushing and areas of the bolt nose that will be soldered.

mapp torch Rem 700 7.62x39

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.

bolt soldered Rem 700 7.62x39

The bolt after the bushing is soldered in place.

machining new bolt face Rem 700 7.62x39

The bolt is placed back into the lathe and dialed in.  The new bolt face is machined with a high-speed steel boring bar.

bolt done on lathe

The bolt face is now the correct size.  Time to install a new Sako extractor.

bolt on mill sako Rem 700 7.62x39

The bolt is secured in a Sako machining fixture on the milling machine.  The centerline and front edge of the bolt are located.

machining extractor groove sako Rem 700 7.62x39

An end mill is used to cut the pocket for the extractor.

drilling extractor sako Rem 700 7.62x39

A .120″ hole is drill through to the center of the bolt.  This retains the extractor in place.

test fit extratcor Rem 700 7.62x39

Now is a good time to test fit the extractor to ensure everything lines up.

drilling ejector spring Rem 700 7.62x39

The bolt is mounted vertically and a hole is drilled for the extractor spring.

7.62x39 green mountian unturned 310 groove blank

The blank is 1.375″ in diameter and 24″ long.  Quite a heavy and impressive piece of steel.

310 blank in chuck

The blank is mounted in a four jaw chuck and indicated to the bore.

60 degree piloted counterbore in 310 barrelA piloted 60-degree piloted center drill is used to bore a mating surface for the dead center.

barrel ready for centerNote the A view of the 60-degree counterbore left by the center drill.

profiling set up

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.

turning the profile between center note feeds and speeds

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.

heavy profile cuts continued for rem varmint contour

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.

pile of lathe shavings

All the turning makes for an impressive pile of shavings!

measuring blank for comparison

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.

measurement sheet

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.

step cuts on profile

This is what the barrel looks like after the series of step cuts.

step cuts second view

Another view of the step cuts.  The black line indicates the end of the straight part of the shank.

file smooths cuts

A lathe file allows me to smooth out the profile.

end of muzzle

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.

blank off of lathe

The barrel when it leaves the lathe.

barrel spinner

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.

barrel spinner on belt

The barrel is held in the spinner and run against a belt grinder.  I start at 120 grit and gradually move up to 240, 320 and 400 grit belts.

left hand slows spinner

My left hand is used to slow down the rotation of the barrel as it is held in the center.

finsihed remington Varmint barrel blank

The finish barrel barrel looks pretty sharp.  A big change from when we started.

measuring actionM700 7.62x39

The action and bolt are measured to determine the headspace and barrel tenon dimensions.

dialing in M700 7.62x39

The barrel is secured in the lathe and dialed in so the bore is concentric with the lathe.

barrel tenonM700 7.62x39

The tenon is cut to accept the recoil lug.

threading tenon M700 7.62x39

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.

finished threads M700 7.62x39

The carbide tool does a great job on the barrel threads.

est fitting action M700 7.62x39

The action and recoil lug are test fit on the tenon.

bolt nose recess M700 7.62x39

The bolt nose recess is cut with a high-speed steel boring bar on the lathe.  This will accept the bolt nose.

test fitting action and bolt M700 7.62x39

Test fitting the lug, action and bolt.

reamer M700 7.62x39

A PTG adjustable reamer stop is mounted to a Manson solid pilot reamer.

cutting chamber 2 M700 7.62x39

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.

bolt closes on go M700 7.62x39

When the bolt closes on the go gauge

bolt stays open on nogo M700 7.62x39

And stays open on the NOGO, the chamber has been cut to the proper depth.

finished barrel tenon M700 7.62x39

After the chamber is cut to the depth, the outside edge of the recess and chamber are broken to aide in feeding.

muzzle dial in M700 7.62x39

To begin work on the crown and muzzle brake, the opposite end of the barrel is dialed in on the lathe.

tenon for Badger FTE M700 7.62x39

A tenon is cut for the Badger FTE brake that will be installed.

threading badger FTE M700 7.62x39

Threads are cut 5/8″-24.

test fitting brake M700 7.62x39

The brake is test fitted to the barrel.  At this point the muzzle brake installation process is complete.

tightening action M700 7.62x39

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.

Bolt in fixture M700 7.62x39mm

The bolt is secured in a fixture on the lathe.  The fixture I am using here is made by PTG.

center drill bolt handle M700 7.62x39mm

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.

cutting off bolt knob M700 7.62x39mm

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.

turning down tenon M700 7.62x39mm

The tenon is turned until it is .313″ in diameter.

threading bolt handle M700 7.62x39mm

A 5/16-24 die is secured in a floating die holder.

completed threads M700 7.62x39mm

As the lathe is run the die advances up the tenon cutting the threads.

finished threads and shoulder M700 7.62x39mm

A high-speed steel 35 degree profile tool is used to clean with the tenon’s shoulder.

test fittimh bolt handle M700 7.62x39mm

The handle fits well.  This is a Badger Ordnance miniature tactical bolt handle.

7.62x39 700blast cabinet

The barreled action is heated, degreased with Brownells TCE, and blasted with Aluminum Oxide media.

preheat 7.62x39 700

After the part is blasted, I take the time to heat it again.  This will help remove oil from the steel.  I use a curing oven to heat my parts.

spray gun 7.62x39 700

The metal is degreased again and Cerkote applied.  I’ve been using this baby spray gun from NIC Industries (the company that makes Cerakote).  It works great!

cure 7.62x39 700

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.

parts out of oven 7.62x39 700

After a couple hours in the oven I can check my work.  This thing is really red!  A red rifle for a red cartridge!

test fit 7.62x39 700

I left the rest of the parts black for a contrast- I may be painting a conservative color….

7.62x39 700 1 7.62x39 700 5 7.62x39 700 close up 1


Build parts are:

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.

best group .918 inches

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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