This is the mil-spec Yugo barrel from Centerfire. It comes in the white.
I had my new barrel hot-blued before this installation proceedure.
I have never attempted this before.
It was difficult to know where to start, but,
It's arbitrary at this point.
I took a long straight edge and drew a
rudimentary centerline with a silver sharpy. It's not perfect, it will serve
as a visual start point on the chamber cut-out. You will note from your
old chamber the orientation of the extractor cut-out. It looks to be
in the 12 and 3 o'clock position. Draw a centerline on the old barrel
across the barrel pin slot and RSB slot. You will note that
the top cut-out corner is left of 12 o'clock by just a smidge.
Scribe this difference onto the new barrel proceeding from
the centerline mark.
After you have established this point, hold up your old Yugo
barrel chamber to the new one and scribe or mark the boundary
line of the lower corner to the new barrel.
Next, to establish the depth of the extractor cut-out area.
I used my calipers to make the actual scribe mark.
.050" is an average I took from 4 different yugo barrels.
There are variations on this cut between barrels as much as .015"
I decided to remove the metal with a tungsten-carbide burr bit
in a dremel. This took it out really fast.
Get the barrel end set up for your own comfort zone so you can
maintain control of the removal process. Take it down almost to the
scribe mark and then leave the rest for file work and clean up.
The roughed-in cut. Use a small file to clean it up.
To demonstrate the fact that the bolt and extractor don't make
contact with this area. Dummy round is inserted for this photo.
Chapter 2, the larch....the larch.
Installing the rear sight block RSB. Center this over the
centerline mark on new barrel. Compare orientation with old barrel
assmbly by looking at the face of extractor cut-out and how it's
oriented under the back of the RSB. Make sure the new alignment
looks to be the same.
Scribe small alignment marks on the barrel and RSB collar
so that you can maintain position while setting it up for
Measure and scribe a line for the RSB's final resting place.
Pressing the RearSightBlock. Make sure and use a softer metal
to separate the ram from the barrel surfaces. I'm using a block
Chap 3.5 Gas Block
Find the placement of the gas-block by installing gas-tube and locking
it in place. Stick GB into tube and hang it outside the barrel to get a
reference scribe mark. This mark is not super critical at this point.
Before pressing on the GB, check visually. Look for parallel lines
across the side with the RSB.
Pressing the gas-block. Press until you reach your scribe
mark. Then remove and install gas tube to insure it will
fit. I had to back the GB off the first time, it was too
tight and would not fit. Don't get it too loose either,
a nice snug fit.
Chap 4 Front Sight Block
Pressing FSB. This takes more acute visual alignment. Sight across
the top and across the sides looking for parallel planes.
Scribe a mark 1.80" back from the face of the threaded barrel end.
This will be the mark to line up the back of the FSB with.
Check alignment after pressing. I screwed on a slant break
after this step just to make sure I didn't have an ugly gap
between it and the FSB after locking into the detent pin.
Chap 4.5 Drilling for Pins
(I sense many builders are nervous about drilling for pins)
forget about it.....
Let's start making chips, .156" bit (shank measurement)
is used on the RSB. Use a new sharp bit for this and
check visual alignment from various angles.
The bit will tend to want to follow the RSB holes because
the barrel is softer. Don't be nervous, this step goes
quickly. I drilled from one side across to the other, it should
zip right across. If it gets hung up, then you must stop
and correct the situation. I've never had a problem with
Drill for the small pins on the FSB and GB, all 4 are the same.
I used a bit .096" (shank measurment) for this.
I used a nail set for the small pins. They should go in fairly easily
just like they came out.
Install muzzle detent spring and pin first before driving side pin.
Chap 5 Hand Guard Retainer
Time for the layout of lower HG retaining pin notch.
I aligned a finished barrel parallel with the new one and
squared across to get a couple marks.
Use a round file to start the notch. Go slow and don't get
sideways. I used the carbide burr to open it up once I got it
Chap 5.5 Drilling Gas Port
I use a hand held drill. Trust the force Sam, or Fred.
You will need a # 27 bit (.142")
Go slow and easy
, keep it in alignment with the GB ports.
Use cutting oil if you want. Make sure not to ram the bit thru
into the opposite side of barrel when it breaks through.
Take a brass bore brush and clean out burrs from drilling.
I had a hangnail in the bore and had to use the blunt, non-sharp end of the
rod to break it loose. Do this very very
gently, this is a new
Finished barrel assembly ready for final pressing, headspacing and drilling
for barrel pin. Mine will be for an M70AB2 Yugoslavian Underfolder,
semi-battlefield pick up look.
Chapter 6 Barrel pressing
Barrel will press into receiver as normal. I lightly apply anti-seize paste to the
inner surface of trunnion. I use Xebec's press kit. The new barrel pressed in
very nice. I edged it in at the front of trunnion where the crest of the chamber
was almost flush with front face of trunnion.
Remove from press and check the headspacing. Insert a No-go gauge and see what
I got it right the first time. Showing a strong 1/2" gap of the bolt refusing to move
forward with the No-Go gauge. I next checked it with a Go gauge. The bolt
closed easily with no resistance. Next, I chambered a dummy round and
it went into battery easily. This is the headspacing method I use on the
7.62 x 39 AK's It has proven reliable on dozens of builds.
Chap 6.5 Drilling for the barrel pin
This will be a replay of the previous pin drilling only on a larger scale.
The stock Yugo bbl pin dia. is .275"
I used an 'I' drill bit (.270") for this step.
Don't get excited. Use a fresh new bit, go slow because the tendency for
the bit to overheat is greater here than before.
I did use cutting oil to keep it cool, and I turned it over and drilled from both
sides to belay the tendency of the metal surface to self harden from
drilling. The trunnion steel is very hard stuff and kept the bit on track beautifully.
I poked a Q-tip with a bit of anti-seize down the pin hole and proceeded to
press. The pressing went very smoothly with just the correct amount of tightness.
Chap 7 the finished build
Battlefield pickup look with new barrel. The scope mount I fabbed myself.
You can do it!