Building a Hybrid Yugoslav M70B1 from a Stub with Screws

Building a Hybrid Yugoslav M70B1 from a Stub with Screws

George Spafford is building a replica of the Yugo M70B rifle using a stub parts kit. A new installment will appear here every Friday

Install the Barrel—Part 2

The Yugo extractor protrudes from the front of the bolt significantly. Therefore, the bolt must be stripped to headspace the rifle accurately. Stripping the bolt is actually very easy and simply requires a small punch and hand pressure to remove the two retaining pins.


Once the groove in the barrel for the pin aligns with the holes in the trunnion, it is time to check headspace. It is always a good idea to use real headspace gauges to be safe. If there is too much headspace, the resulting slop on the end can cause cases to bulge and even rupture. When I first started building AKs, I invested in a set of Manson Precision Reamer gauges—Go, No-Go and Field. They have worked great for me over the years and are a good investment.


With the Yugo bolt, the extractor is so large that the bolt must be disassembled to test headspace. Despite looking daunting, the M70 bolt actually disassembles with hand pressure by removing first the bottom pin and then the crosspin. I like to do this on a table to make sure I don't lose any little parts and then I put the parts in a container out of the way. A little organization can save some grief down the road.

Use a small tray to hold the bolt parts. They are small and very easy to misplace.

I like to perform headspace tests with just the bolt and no carrier. This way I can see exactly what is going on. First, I use the Go gauge to verify that the bolt will close properly. I insert the gauge in the chamber and then slide the bolt forward rotating it so the lugs begin their lockup.


The bolt should be able to rotate fully. If it does not, the barrel must be pressed back out. Methods include a long bolt with a double brass nut on the end to protect the breech, the use of a long socket extension with a stack of copper pennies taped on the breach to protect it and so on.

Second, I use the No-Go to verify there isn't excessive headspace. Again, I insert the gauge in the bore, install the bolt and proceed to rotate it. The bolt should stop short of full rotation. Now this is an estimation on my part, but I would say mine stop at around 80-90% of the rotation. We're talking differences in the thousandths of an inch, so I really am watching to make sure it doesn't go all the way—that is the important part. If it does, then the barrel must be pressed in further.

Most likely, with a worn M70 like mine, you will need to press the barrel in further. Any time you change the location of the pin from the original means you will need to use an oversize pin. This is done by making sure everything is in the right location and then drilling a new oversized hole with a sharp cobalt bit that is .002" smaller than the pin.


For this build, I had too much headspace, so I pressed the barrel in and opted to use 19/64 (.297") drill rod and M size drill bit (.295"). Once it was pressed in, I confirmed the headspace one more time before moving on. It's always good to play it safe.

GET THE NEWSLETTER Join the List and Never Miss a Thing.

Recommended Articles

See More Recommendations

Popular Videos

Performance Center M&P Shield M2.0

Performance Center M&P Shield M2.0

From Smith & Wesson, the M&P Shield M2.0 is a great option for a carry gun with optics option.

American Suppressor Association (ASA)

American Suppressor Association (ASA)

ASA is the unified voice of the suppressor industry and a leading subject matter experts on suppressors and suppressor related advocacy.

New Bushnell Prime 1700 and Nitro 1800 Rangefinders

New Bushnell Prime 1700 and Nitro 1800 Rangefinders

Jake Edson of Bushnell Optics tells OSG's Lynn Burkhead about the brand new Prime 1700 and Nitro 1800 rangefinders.

Kyle Lamb and Eric Poole talk SIG pistols

Kyle Lamb and Eric Poole talk SIG pistols

G&A Editor Eric Poole and Viking Tacticals's Kyle Lamb talks about 2 new pistols from SIG Sauer and a Lipsey's Special of the P365.

See More Popular Videos

Trending Articles

CRKT makes 17 different knife models exclusively for Ruger, from fixed hunting knives to tactical folders, and many of their models are offered in several different styles. Accessories

Ruger CRKT Knives Review

James Tarr - July 08, 2019

CRKT makes 17 different knife models exclusively for Ruger, from fixed hunting knives to...

Want the “Holy Grail” of AR-15 rifles? Brownells has made that possible with their BRN-Proto retro rifle. Rifles

Brownells BRN-Proto Retro Rifle

Patrick Sweeney - July 02, 2019

Want the “Holy Grail” of AR-15 rifles? Brownells has made that possible with their BRN-Proto...

No one can restore receptivity to another Trump term with these disaffected gun owners but the president himself. 2nd Amendment

2020 is Trump's to Blow with Gun Owners

David Codrea - July 09, 2019

No one can restore receptivity to another Trump term with these disaffected gun owners but the...

The last of Germany's infamous Elefant tank destroyers. Historical

World War II German Elefant Tank Destroyers

Neal S Shera - July 12, 2019

The last of Germany's infamous Elefant tank destroyers.

See More Trending Articles

More Gunsmithing

Lone Wolf Distributors are now offering the Advantage Arms .22 Conversion Kit for Glock pistols. Gunsmithing

Lone Wolf Advantage Arms .22 Conversion Kit

SGN Online Editors - April 16, 2014

Lone Wolf Distributors are now offering the Advantage Arms .22 Conversion Kit for Glock...

In the second part of this series, we examine how to build the barrel assembly on an AR-15 varmint upper. Gunsmithing

Building a Heavy AR-15 Varmint Upper Part 2: Barrel Assembly

Gus Norcross - December 31, 2013

In the second part of this series, we examine how to build the barrel assembly on an AR-15...

This fully adjustable stock and comb for AR-15/M16/AR-Style .308 rifles readily adapts length of Gunsmithing

Brownells AR-15/M16/AR308 PRS Buttstock Kit

SGN Online Editors - September 15, 2014

This fully adjustable stock and comb for AR-15/M16/AR-Style .308 rifles readily adapts length...

YouTuber, GunCraft101, builds an AR-10 from used brass casings. Gunsmithing

YouTuber Builds AR-10 Receiver from Used Brass Cartridge Cases

Jim Grant - July 06, 2018

YouTuber, GunCraft101, builds an AR-10 from used brass casings.

See More Gunsmithing

GET THE MAGAZINE Subscribe & Save

Temporary Price Reduction.

SUBSCRIBE NOW

Give a Gift   |   Subscriber Services

PREVIEW OUR CURRENT ISSUE

GET THE NEWSLETTER Join the List and Never Miss a Thing.