FAL G1 problem

[roysha]

I cannot get this G1 to cycle. The rifle will fire and sometimes the bolt will move, perhaps 1/2"-3/4", but most of the time it doesn't make any discernible movement. However, the action operates freely when the fired case is ejected manually.

It is a gun built using a very good condition G1 parts kit and a new DSA G1 receiver.

I have built quite a few FALs, both metric and inch, over the years and have never had one that would not function reliably, until this one.

Here is what I have done to try to figure this out:

Before someone comes up with this stroke of wisdom, YES the "A" on the gas plug is up. But just for boogers and giggles I turned it to see if it would make any difference. Nope.
Checked the rat tail and it is not bent or dragging anywhere in the action cycle.
Pulled the gas block to make sure the port in the barrel and block were clear and properly aligned. Checked port diameters and they are in spec. Inspected for cracks or anything else that could lead to a leak.
New gas tube which indexes tightly, with the notch in the proper position and holes a 10&2.
Piston slides freely through the gas tube and receiver.
Unscrewed the action spring tube and made sure the notch was properly located.
Cleaned everything squeaky clean and lightly lubed.
Polished the chamber incase there was a bit of roughness even though the cases did not indicate any.
Tried several different magazines incase there some was issue there.
Test fired with some HOT Portuguese military surplus ammo that has never failed to function any auto loader I have fired it in (except this one) and that has been some pretty ratty guns on occasion. Also test fired with factory, National match and some reloads I use in my other G1.
Test fired with the gas adjustment nut full closed and full open on the theory that perhaps it was getting too much gas and trying to open the bolt while the chamber pressure was too high.
The gas block is correct metric and has the correct gas plug which fits as well as any FAL that I have ever built so I don't think there is a gas leak there.
Tested with both new Tapco and original MIL gas piston.
As I stated above, the action operates freely, manually, with no binding anywhere.
Searched the internet for advice and found a lot, which I applied. but to no avail.

Quite simply, I'm at wits end. Any suggestion would be greatly appreciated. (I don't need the one that says just find someone that wants the rifle more that I do because there isn't anyone. I really want to get this rifle operational)

[MtGun44]

Clearly the gas piston is not punching the carrier hard enough, so
let's look at what can be wrong. Since you have changed the piston, I
suggest that somehow the cylinder is oversized or the gas is leaking
at the joint between barrel and gas system. These seem to be the
only things left, assuming I read your post correctly.

Bill

[roysha]

Thanks for the thought but I have done the tissue paper test with no indication of any leakage. Piston clearance in the block is, according to my measurements, less than .001" so I don't think it is leaking around the piston head.

[45 2.1]

Are you sure gas is getting to the piston?

[randyrat]

Obstruction before the gas tube?

[Del-Ray]

Do you have any more parts kits maying around, or another rifle you could switch a few with? My FAL is an FN paratrooper and I'm stumped as to what it could be after everything you've said.

Could your bolt lockup area have a burr or something else that is holding up the bolt long enough that the pressure in the system has bled down too low to properly open the bolt? That's the only thing that I can think of right now.

[Artful]

If you got another G1 I'd start swapping parts

Also try http://www.falfiles.com/forums/index.php

[roysha]

Indeed, I have checked the alignment of all the various holes and can run a wire through everything into the bore.

I have another gas block that appears nearly new. I also have another DSA G1 upper. First I'm going to swap out the gas block. I have avoided doing this simply because I was hoping there was something simple I had overlooked. Apparently not. If that doesn't help then I'm going to tear down the upper assembly and install the other G1 upper. If that doesn't help then I am going to incrementally open up the port in the barrel. According to one site, I can open it as much as 1/8" although that will be a last resort since there is no return from that.

If there are any burrs or other boogers that might impede the cycling, I sure can't see or feel them. As I stated above, it cycles smoothly and easily, manually. That is what is so puzzling to me. It feels very similar to my other G1, an acquaintance's SA58 and another fellow's Imbel.

[Postalpaul]

Headspace ??

[MtGun44]

Short oprod/gas piston? Is there a spec on the protrusion of
the oprod rear face, similar to firing pin protrusion specs?
Seems like a oprod spring with a few too many coils could
stop it by going solid too soon.

Compare # coils and fully compressed length of a couple of
springs. Remove the gas plug and push the piston all the
way back until it hard stops. Remove spring and see how far it
can protrude, see if this is the same as one that works.

Bill

[gew98]

Any chamce you have a bad barrel with a chamber flaw and or a too small gas port drilled in it ?.

[Multigunner]

Do the rims of those cases that do extract show damage that would indicate premature attempt to open before residual chamber pressure has dropped?

Australia used only single base powders for their FAL clones because ball powders generated a too high gas port pressure. Don't know about the Canadian FAL ammo but Canada uses single base powders for their 5.56 mm ammo to avoid the same problems with their AR clones.



Test fired with some HOT Portuguese military surplus ammo that has never failed to function any auto loader I have fired it in (except this one) and that has been some pretty ratty guns on occasion. Also test fired with factory, National match and some reloads I use in my other G1.
Matchgrade ammo I fired from a STG58 consistently showed rims nearly torn off due to premature unlocking. Some Portugese 7.62 ammo I broke down was badly degraded. Don't know for sure but I've heard they used some old stores of German powders for some of their 7.62 production.

Try fresh M80 Ball or if possible the Australian equivalent.