Workbook

discoloration at the joint. Shut the torch off and repeat the steps above. If the barrel still does not

move, you are stuck and will have to find someone to do it right, using a hydraulic barrel vise and a

form-fitting receiver wrench.

To avoid marring the barrel, you must use a fitted wrench on the flats in front of the receiver face. 1-

1/16" and 27mm are pretty close and can be filed to an exact fit. Ideally, it will be so tight you

actually have to tap it with a small hammer to get it on the flats. A poorly fitting wrench will slip and

round out the flats. In most cases, a crescent wrench is too loose. If you insist on using one anyway,

select the largest you can find - 12" or longer handle. Tighten the crescent wrench around the barrel

flats. Then remove the wrench and tighten it a tiny bit more. Then tap it on. You can also file the

barrel flats to fit whatever size wrench you have. Although still marring the barrel, it is not as

unsightly as gouges from pipe wrench jaws. Follow the same heating procedures, if necessary. After

the barrel is off, clean the crud from the barrel threads and degrease it.

Make sure you have the handguard retaining ring (socket, rear handguard) on first. Can't count the

number of times I did a perfect barreling job, then noticed the retaining ring still sitting on the bench.

You can pull the front sight on inch/metric to install from the front, but you must pull the barrel again

to install the Israeli heavy barrel. All receiver rings are not the same size. Test fit first. The Israeli

FALO is different from the standard metric, and Commonwealth and Belgium styles vary slightly.

Spin the barrel on and note where it stops.

Ideally, you will fabricate a receiver wrench such as the ones shown, or following the plans included

in the schematics section of this workbook. If you are putting the receiver in a vise, have the stripped

bolt carrier (slide assembly) and cocking handle slide in place so you don't pinch the rails. Two bolt

carriers, the front one a paratrooper or standard with rat-tail removed is better. The barrel should end

at 11'oclock. If it doesn't do the following:

GENERAL. I never was particularly good at math, but there are some calculations that may

put into perspective what we are doing when timing a barrel. There are 360 degrees in a

circle. There are 12 points to a clock, therefore the distance between 11 o'clock and 12

o'clock is 30 degrees. Your barrel is 1" in diameter and threaded at a pitch of 16 threads per

inch. The distance peak to peak on each thread is 1/16 inch, or .0625". Therefore each

complete rotation of the barrel moves it .0625" closer to the receiver. When the barrel

shoulder is flush against the receiver and torqued down, but the front sight is not pointing

directly up at 12 o'clock, then the barrel is "out of time" either too short or too far. You

change the timing by removing (or adding) material to the shoulder. Since .0625" is one

complete revolution, each degree of timing is approximately .0002" of shoulder material, and

each clock position (30 degrees) is approximately .005". At approximately 100 foot pounds

of pressure, the barrel will turn a bit less than 30 degrees past the point where it stops under

hand pressure. The barrel should hand tighten to approximately the position shown in the

photo below. A one degree error manifest as approximately 3" off at 100 yards.

INCH PATTERN. Select an appropriate sized breeching washer from your extensive supply

or go to hardware store and purchase a few steel washers with a 1" inner diameter. Steel

shim stock can also be used. If thin enough, you can cut with shears. Sand or grind the

outside diameter of the washer to 1.25" or about 31mm. Then flat sand washer until barrel

will stop a bit past 11 o'clock, between 15 and 30 degrees short of top dead center. Change

the direction of sanding frequently and do both sides to keep it flat and parallel (who needs a

surface grinder!). If your wrench turns the barrel past 12 o'clock, then start over testing the

fit more frequently. If not far enough, keep sanding.