View Full Version : FAL bolt won't cycle

May 29, 2008, 20:55
i have an Imbel FAL thet won't cycle the bolt regardless of regulator position.
when it first started malfunctioning, went home and completely disassembled and cleaned thouroghly the barrel, gas system, bolt and carrier, chamber, gas port, you name it. you know, the usual things you do when they don't autoload every round.
back to the range, no luck. this time won't even eject spent round. sometimes extracts them 25%, sometimes not at all.
i'm thinking 'surplus ammo too old'? no, chronoed south african, australian and portugese ammo, all good.
now i'm thinking hard extraction(tip from former canadian infantryman). back to the bench for another chamber cleaning. same result. working the cocking handle manually extracts them fine
'did i turn the gas tube in too far, partially blocking gas flow'? no joy there.
an email to the builder with a similar explanation came a reply "i think you have a gas flow problem". no s..t dick tracy! though i'm wondering if it could be something else.
help please!

May 29, 2008, 21:25
Check that the gas tube retaining pin is indeed in the proper position. Unscrew the gas regulator all the way and you will be able to see it. If it is missing, it's likely the gas tube could have rotated to cut off the gas flow.

Be sure the bolt and carrier move freely. Since you said it cycles by hand just fine, I'd assume this is not the problem.

May 29, 2008, 22:22
yes the tube retaining pin is properly located.

Mosin Guy
May 29, 2008, 22:58
http://www.falfiles.com/forums/showthread.php?s=&threadid=108077 Among the most common symptoms of FTF/FTE (failure to feed, failure to extract) are the following:

1. Bolt riding over the cartridge either causing a jam or missing the cartridge altogether

2. New cartridge only partially chambers, spent casing extracts and may or may not eject

3. New cartridge jamming against back of receiver

4. No apparent movement of bolt or carrier regardless of gas setting

5. Partial extraction of spent casing regardless of gas setting, casing jams hard in chamber

6. Gas tube blows out of gas block

7. I've done all the stuff to get more gas but my FAL STILL won't cycle properly.

8. Bolt closes easily on headspace guage but will not chamber round. Jams up tight.

FIRST, have you checked and made sure that your extractor hasn't broken?

I will deal with them in order.

Before you do anything, ensure that the rifle is assembled correctly and there are no broken parts.

1. Bolt riding over the cartridge – This is a FTF problem and can almost always be traced to three common problems.

a. First, check to see if the magazine is being held in the mag well tightly. If it is loose, your problem is most likely a mag catch that is too short. The solution is to replace it with one with an extended mag catch. Tapco offers extended mag catches for about $10. Alternately you could weld a small bead on the end. In either case you will have to “file to fit” for a good tight hold.

b. Second, take the bolt and carrier out and remove the dust cover and close the rifle. Insert a mag with at least two cartridges into the mag well. Now look at the mag from the top of the receiver to see if the mag looks like it is symmetrically positioned in the well, especially near the front. Most often it is well used mags that have this problem which will manifest itself as a FTF from one side of the mag or the other. Also, check the mag for a weak spring. In either case. Get a new mag and throw this one away. (Yes, you can replace a weak spring if you have another bad mag laying around but at $10 each for new mags, it is hardly worth it.)

c. Third, look for long fairly deep scratches in the cases of cartridges that have jammed. This is usually caused by sharp edges on the feed plate at the top of the mag well and more often on cartridges that feed from the left than the right. Polish the edges of the feed plate with 400 grit wet or dry or finer.

2. New cartridge only partially chambers, spent casing extracts and may or may not eject

a. If the spent casing eject reliably, check to see if the bolt carrier moves easily in the rails. Imbel GL (gear logo) receivers are well made but a common problem is that the receiver rail is directly beneath some of the lettering stampings and occasionally gets distorted from an over zealous machine operator. Gunplumber suggests taking a small bastard file and gently but firmly filing the “hump” off.

b. If you have an aftermarket HTS (hammer, trigger, sear) combo installed, remove and replace them with the pieces that were provided with the kit for troubleshooting. Century is not known for tight adherence to tolerances and their HTS will often cause FTF problems because they drag on the bottom of the bolt or carrier.

c. Make sure that the recoil tube is straight and undamaged and that the spring and recoil plunger are lightly greased. A small amount of grease will not cause the rifle to lock up.

d. Check for weak recoil spring. R&R as necessary.

e. Perform gas checks in Number 4. c, d, e, f, and i.

3. New cartridge jamming against back of receiver

a. This is most common with Century receivers. I have bad news, there is a problem with the design of the feed ramps that cannot be fixed easily. Polish the feed ramps with a felt tip and rouge on a Dremel and it may fix it. Others have suggested MIG welding or brazing a small ramp and Dremeling it to shape. Proceed at your own discretion.

b. This can also be a problem caused by a slightly out of spec barrel. The barrel around the chamber cut should have a bevel about 1/8" wide. You can widen it slightly with a small file and polish it with fine sandpaper and then a felt tip and rouge on a dremel.

4. No apparent movement of bolt or carrier regardless of gas setting

a. Check that the gas plug is in the “A” position.

b. You DID remember to put the gas piston back in, didn’t you?

c. Check to make sure the gas tube is pinned in place and has not rotated. Ideally, the exhaust ports in the gas tube should be at 8 o’clock and 4 o’clock but if they are at 10 and 2, it will not affect operation.

d. Ensure that the gas port is not obstructed.

e. Check that gas piston is not undersized or worn. Proper diameter is between 0.429” and 0.431”.

f. Excess leakage around gas tube, see No. 6

g. Check that the bolt carrier “rat tail” is straight and in the recoil plunger detent and not jammed against the back of the lower receiver when closed.

h. Take the gas piston spring out and roll the piston on a flat surface to check for straightness. Reinstall the gas piston with the bolt and carrier removed. The piston should fall freely through the gas cylinder and gas nut. If not check gas tube and gas nut for roundness and damage.

i. Check for cracked gas block.

j. Make sure you haven't put a metric gas plug in an inch gas block. A metric gas plug is about 3/16" longer than the inch plug. The gas plugs are not interchangeable.

5. Partial extraction of spent casing regardless of gas setting, casing jams hard in chamber

a. This is most often a problem of not enough gas. What is REALLY happening is that the spent casing is going back a small distance and then being pushed back forward into the chamber and shares solutions with No. 4. c, d, e, and f above.

b. Check that the gas piston moves freely. See 4. h above.

c. Check that carrier moves freely. See 2. a, b, and c above.

6. Gas tube blows out of gas block. This is a common problem in the G1 kits and the solution is both simple and cheap.

a. First, clean the thread of the gas block and gas cylinder and spread a small amout of solder flux on the threads.

b. Install and pin the gas tube with the exhaust ports at 4 and 8 o’clock on the rifle as if you are preparing to shoot it without the gas piston or spring installed.

c. Using Mapp gas, heat the threaded area and apply silver solder (preferably high temp silver solder because it is stronger) until it flows into the joint.

d. After the area cools, clean the excess flux off the area (some flux is acid based) and you may file the high spots off the solder with a small file if your solder job isn’t too pretty or interferes with the gas regulator.

e. With a Dremel cut off wheel, cut the gas tube off about 2 inches from the back of the tube (the end closest to the receiver) and discard it. Use sandpaper to smooth the end off.

7. I've done all the stuff to get more gas but my FAL STILL won't cycle properly

a. Okay, one more trick to get more bleed gas. Remove the gas plug, piston, spring and tube. put a 1/4" wooden dowel down the barrel.

b. Starting with a #41 or so drill bit insert it BY HAND through the bleed hole in the gas block and use it to determine the size of the gas port hole in your barrel.

c. Once you have determined the approximate diameter of your gas port hole, take the next larger drill bit and use it to ream the hole out. Keep the drill speed slow and use plenty of cutting fluid and you will be less likely to break your drill bit off in the hole.

d. Test the function of the rifle once you have gone up a couple of sizes. You should see some improvement. You can increase the size of the hole up to about 0.125" untill you get enough gas for proper operation.

8. Bolt closes easily on headspace guage but will not chamber round. Jams up tight.

a. Does a cartridge fit into the chamber when you feed it by hand?

No. Clean chamber thoroughly. Ensure cartridge is in spec. Lastly, you may need to ream the chamber slightly.

Yes. It could be the top rear edge of the bolt binding up against the top inside of the carrier. Put a piece of Playdoh or some other putty on the inside top rear of the bolt carrier and then put the bolt in the carrier. Put them both in the receiver and try to push it closed with a cartride in the bolt until it binds. Pull the bolt and carrier out and observe the Playdoh. Is it pinched all the way to the carrier? If so, file a small amount off the top rear of the bolt until it clears.

May 29, 2008, 23:06
What barrel length?
Could this simply be a rifle with a shortened barrel, and a too-small gas port?

I've never heard of a gas tube being screwed-in so far that it obstructs the gas port. If you think there is any chance of this, I suppose you could file the notch on the forward end of the tube a little deeper. Still, I'd be very, very surprised if that is the problem.

The correct method of installing a gas tube is to screw it in until it bottoms out. Then unscrew the tube until the flat edge of the threaded end is in the proper position for the gas block to receive the gas-tube retaining pin.

For gas tube assembly, see generally:


May 30, 2008, 02:42
"A" on the gas plug is on the top, right?

May 30, 2008, 06:15
weapon has a normal 21" barrel, and has been properly assembled.
my gas piston measures .432".
i believe i've tried with no magazine but can't remember. i'll go out back this evening and try with no mag and different one, though they feed fine when cycled manually.
functioned flawlessly for 5 years and hundreds of rounds on a regulator setting of 4.5 to 5.
by the way the weapon was built by AZEX.

May 30, 2008, 11:33
Originally posted by thedrickel
"A" on the gas plug is on the top, right?

^ It would help to check this before you proceed any further. :D