By Dennis Sandoz, GCA Silver Member
Two Yugo Model 48 Mauser rifles with original barrels had found their way into my gun safe. Unfortunately, they both had bad barrels, evidenced by visual inspection and a 50 yard group (pattern?) size in excess of 12 inches with iron sights. The only lathe in my home shop is a ShopSmith Model 10ER manufactured in 1952 so I decided to modify it to be able to cut metal and enable the fitting of two new fully chambered barrels to the existing actions.
Fortunately for this project a cargo container of original replacement barrels manufactured by Zastava in Kragujevac, Serbia, during the 1960s, was imported into the USA during 2012. I was able to purchase two of these new barrels with the original military contour for a total of $80. This was my first barrel fitting project so I made a number of phone calls to Jack Landis for technical advice as the project progressed.
The Barrel Vise and Action Wrench used in this project were purchased from Brownells (catalog part numbers 080-860-205 and 080-800-098, respectively). The only other tool I needed was a cheater bar to remove one of the actions. An old piece of galvanized pipe served admirably and this step of the project was routine.
Truing the front of the receiver was accomplished with the mandrel purchased from Brownells (catalog number 080-098-001). In the picture on the left below you can see the set up with the ShopSmith used for this step of the project. Converting the ShopSmith wood lathe for metal applications involved mounting a Harbor Freight 6″ Cross-Slide Vise on a steel plate clamped to the ShopSmith carriage and the purchase of a mini-lathe tool post and cutting tool set.
I made a fixture from a piece of scrap angle iron to hold the action in my bench vise for lapping the bolt lugs. Brownells catalog number 080-097-198 Bolt Lapping Tool set for the Large Ring Mauser was used with 600 grit lapping compound to obtain about 80% engagement on each lug.
The next step was to assemble the barrel and receiver and check the headspace. One thing many people are not aware of is that in 1980 the specification for the 8mm Mauser chamber shoulder angle changed. When you order a new headspace gauge today it is made to the current specification which is not appropriate for a rifle made to the old specification such as a WW I or II Mauser or the new barrels I purchased that were made in about 1960.
The old specification drawing is very hard to obtain so I have included both drawings here for reference. (CLICK HERE to download these full size drawing as a pdf file. The page size is 8-1/2 by 11 inches so you can easily print and keep this reference. — editor)
The first rifle I assembled had acceptable headspace without any additional machine work! This is pretty rare but with a Mauser action three things need to match up so I still had some machine work to do. When fitting a barrel to a Mauser action it is necessary to have the breech end of the barrel hand tight against the internal receiver ring with a 0.002″ gap between the front of the receiver and the barrel shoulder. This needs to be accomplished in addition to acceptable headspace.
After careful measurement and consulting my ‘go to’ expert I concluded that I was about 0.003″ out of specification and needed to remove about this amount from the end of the barrel where it butts against the internal ring in the receiver.
The question was how to accomplish this with the equipment and tools on hand. I decided to use my ShopSmith and a very fine file to accomplish this task.
The breech end of the barrel was supported by the lathe tail stock containing a copper pipe fitting packed with grease that was used as a bushing to center the barrel in the tail stock and not ruin the barrel finish. A dial indicator was mounted in a vise to center the barrel muzzle in the 4 jaw chuck.
Next, I put the barrel in the barrel vise and tightened the receiver so that the 0.002″ gap between the front of the receiver and the barrel ring disappeared. This 0.002″ of crush is the specified tightening torque for the barrel to the receiver.
The next step is to mark the location of the extractor slot that must be cut in the breech end of the barrel.
Now I was ready to mark the extractor slot location and mill out the slot.
The Harbor Freight Cross-Slide vise worked very well for milling the extractor slot. I simply unbolted the barrel vise from the bench and clamped it in the cross slide vise. I set up the ShopSmith with its drill chuck and used an end mill bit. Using a 7/16″ or ó” cutter would allow the work piece to be shimmed vertically just once.
The photo above shows my Yugo 48 project rifle with a Karsten adjustable cheek rest installed. The only things left to do are install a recoil pad and apply a finish to the new barrel. I fired a total of 10 rounds to completely sight in the new scope at 50 yards. The target below includes the last 5 rounds.
The center to center group size for five rounds is 0.675,” for four rounds the distance is 0.360″ and for three rounds the distance is 0.281″. Not bad considering the rifle at this time still had the standard military trigger, far from ideal with a trigger pull of 5.5 lbs.
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