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View Full Version : Here we go again - Unwanted full auto on a semi.


yankytrash
September 09, 2001, 13:48
Broke out my L1A1 after a month and half in the safe. Right from the git-go on the range, it went full-auto all the time.

First, I thought it was just(?!?) a burst, from the grease being cold and trigger group getting a little sticky. We giggled and I tried again. Three shots. I decided to cinch up my nads and try to hold the trigger through a mag, or until it stopped. It went full-auto through a full 20-round mag. I tried another magful - same thing.

That was fun as hell, but I better fix it before the neighbors start calling the three-letter fearies.

This gun functioned flawlessly went I used to shoot it alot. I've put about 2500 rounds through it, and it's been fine. I thoroughly clean it and oil/grease it after every shooting session.

When I got it back home, I searched the archives here and found a few things to check. Problem is, I can't get it to do it again through working the action by hand.

Is there something else I should check or replace? I've looked for burrs, chunks of crap in the lower, rust spots, broken springs, and sticky areas. I've found nothing. I suspected slamfire from a bent pin, but the pin and spring are fine. I'm duped.

Could something be wore out or need adjusting after only 2500 rounds? This gun is a brand new (when I bought it) Century L1A1 on an Imbel receiver. I've heard bad things, but up to this point I have yet to have an accuracy or function issue.

If I can get some good leads, there's a gunshow coming up this weekend where I can probably find a couple replacement parts.

Mosin Guy
September 09, 2001, 13:54
It has to do withe the engagement of the Centry hammer trigger and sear,its an easy fix just change out your Centry trigger group(Junk) with a new FSE(Very Good) trigger group they are about $50.00 and Tapco has them or you can buy them direct from FSE.

Derby FALs
September 09, 2001, 14:00
If you have a FN sear laying around, try it first.

yankytrash
September 19, 2001, 18:44
Alright, I have a completely new trigger/sear, hammer, and selector lined up. I'm gonna pick it up this Saturday.

While I wait, I decided to try to fix it myself. I figure it's messed up, so all I'd be doin is messin it up more, right? Right:

I know it's gotta be the sear and hammer engagement. The hammer notch looked a little more beat up than the sear tip, so I started there. I filed the notch slightly.
I put it all back together and tried some dry firing (this thing ain't gonna see the range again until I get the new trigger group).
Now it releases the hammer on both the trigger pull and the trigger release as I work the action.

Now, I understand how the complete lower works and synchronizes, but I can't understand for the life of me how the thing can release the hammer on every trigger release, regularly like it was meant to do it or somethin.

Can anybody shed some mechanical light on this? Meanwhile, I'm gonna start filing the trigger sear. :D

yankytrash
September 19, 2001, 19:02
I think I might be onto something.

The tip of my trigger sear is at a bit of a forward angle. I decided to try filing that back. You know how hard that metal is?!? VERY hard. After just barely filing the pointiness off the sear, I gave up.

I put it all back together and decided to try a few dry-fires. Works fine now. Now I'm even more confused.

Is this sear elongegating?

:confused:

Brian in MN
September 19, 2001, 19:23
Quit with the full auto, yankee. It is not safe to fire them without an auto sear.

W.E.G.
September 19, 2001, 19:28
Very unsafe.

Out-of-battery discharge is quite possible under this condition, and will likely damage your rifle and may cause personal injury.

yankytrash
September 19, 2001, 21:06
Erruhhh, "quit with the full auto"?, "out-of-battery firing is quite possible"?

Did you read my first post? The out-of-battery firing and full-auto bursts ARE the problem. I'm trying to find fixes here, thus the filing.

I started filing certain areas that I thought may be a problem, and the problem seems to have gone away. Although I have a fairly good idea about what's happening, I wanted to be sure. I only wanted somebody's opinion on what exactly was happening with the hammer releasing when I let go of the trigger - to make sure I know what the fix is if it does this again.

I've never considered a 'fix' to be "replace all the parts until it goes away". If that were the case, another easy fix would be "don't buy $500 Century guns, only buy $1500 DSA's". A fix is finding the problem and solving it to save money, not spending mounds of money to replace unbroken parts.

I have a Century L1 on a LEGAL Imbel receiver. There have been no modificatrions at all to this gun, unless you count a rear sling swivel as a modification.

I don't mean to sound like a jerk here, but come on guys. I posted a legitimate problem and wanted a fix for it.

I see now why I have to spend hours in the shop tinkering with things to make them work again - there's no help out there for a guy like me that really needs it.

Go back to your elitist kit guns, I guess I'll just have to mind my own business from now on. If anyone has an honest observation about my problem, and why filing the trigger sear tip fixed it, please email me. I haven't been back on this board for awhile now, and I'm remembering why now.

W.E.G.
September 19, 2001, 21:17
Easy there. You might bust the sphygmometer!

I wouln't conclude that your file work "fixed" the h/t/s problem until you run it with live ammo. That creates a catch-22, as the rifle may be unsafe with live ammo.

We're just regular guys around here. Were you looking for something more? If you find it elsewhere, let us know. I'd like to check it out.

floatingFAL
September 19, 2001, 21:32
Does make you wonder doesn't it.The replies that is.You were very clear about trying to fix the problem if they have no more attention to detail than that their advise
might not be so good.You're on the right track with the new pieces but if you want to
keep messing with the old use a stone not a file.Works much better.Good Luck
Ryan

usmc326
September 19, 2001, 23:27
What's with a few guys suddenly having
an attitude? Bill has been MIA since he got spanked in Dumping Brass.

Anytime ANY firearm goes full-auto the first suspect is the sear. A classic example is the 1911 .45ACP when a novice trys to smooth up the action.
NEVER use a file on the H/T/S, as it removes too much, too fast, and doesn't leave a smooth finish even if it looks smooth. India stones, or the
multi-stones from a Lansky-type knife sharpener will do. Only stone any burrs on the metal faces, do not do it just to smooth the trigger, as it takes an experienced smith, familiar with THAT firearm to do it correctly.

Century rifles used Hesse H/T/S's, and
Federal Arms might still sell them. Those that bought them found the parts to be out-of-spec, with elongated or not quite centered holes, and "soft".
Even FSE experienced problems with some of their FAL & AK H/T/S's not being properly heat-treated. The FSE
sets now available are fine.

My guess is that your Hesse components
have finally worn just a tad to alter
the Sear's face, causing the rifle to go full-auto. Buy an FSE H/T/S set from Tapco or RPB. I'd lean towards Tapco, as their service is better.
Even some DSA's & custom rifles have
experienced broken hammers, from 70-2,500 rds. It's kind of the "luck of the draw", but the "smiths" at Century butchered alot of the internals to get the parts to fit, not to get the guns to fire. You missed all of the guys that had to return their's for 3 months of warranty work.

I think the Century rifles were a best
buy, as the only problems were bending gas pistons & the occasional internal problem, all of which can be replaced for well under $100. So, for $600, half the cost of having one built, you
have an FAL.

Derby FALs
September 19, 2001, 23:50
Save yourself some hassle and grab a set from RPB USA (http://www.rpbusa.com/FNFAL/FNFALs.html)

These parts are US and dropin.

herman07
September 20, 2001, 00:12
I has the same problem with my Century h/t/s. Mine started at assembly and never got to the range for the "go fast" like yours did.

I fit and filed and cursed the parts until they worked properly dry, then test fired. No problems yet after about 1500 rounds. It appears that problems may develop later though. The FSE parts were not readily available at the time of my build (or I was not aware of them yet), but I think that I will invest in a set to keep in case the Century parts exhibit the problems you mentioned.

Good luck.

yankytrash
September 20, 2001, 05:32
Thank you. I went against my normal policy of 'think twice, post once' when I posted that last one. I apologize for blowing off at the handle and being a total jackass. The trouble and the fix was confusing me enough, and when I thought I was being wrongfully accused of converting my baby to full-auto, it sent me.

I'll finish off the sear and hammer with my honing stone, as suggested. I'm still gonna pick up that lower kit this weekend, just in case.

I'm sure that my sear and/or hammer must be softer than some, because I was able to look inside an FAL parts bin at the gun show last weekend (droooooollll). All the hammers and trigger sears looked and felt to be more hardened than mine. They had a *ping* instead of a *clunk* when tapped with a metal object. I'da picked up the parts I needed there, but I believe I need US parts. Mine are all marked with the "C", designating US internals (correct?). She'll have my US internals this weekend.

ByronF
September 20, 2001, 07:18
Hey YankeeTrash. I think it was Gunplumber who described how a semi FAL can go FA instead of just having the hammer follow the bolt home. I probably won't describe it as well as he did but I'll try. And I could be flat wrong. If this is correct the credit goes to GP.

If your hammer/sear engagement was sufficient your rifle would work fine when cycled by hand as well as under live fire conditions. If your engagement was total crap it'd fail when hand-cycling the action and the hammer would never hold back long enough to fire a round.

However, with marginal hammer/sear engagement your rifle will seem fine when cycling it by hand and dry firing it. The problem will only show itself when shooting. What happens is the carrier cocks the hammer, which is barely held by the sear. When the carrier then smacks the bolt into battery the impact jars the hammer free of the trigger, going FA. When you let off of the trigger the cycle will stop because the sear captures the hammer on that other notch, which has not yet been buggered up by the FA firing.

This type of failure would seem to be progressive and will get worse, although it sounds like you've reached the zenith of hammer/sear failure. I replaced my set when it first started to double and triple but I'm sure it would have eventually reached your condition.

W.E.G.
September 20, 2001, 09:18
I could never get my Century hammer to work. I use it for a fishing sinker now.

But the Century trigger and sear work swell with the foreign hammer. Probably the best trigger "feel" I have (on a FAL). Smooth, consistent, and not real heavy. Better than DSA. Better than FSE.

While we are talking about triggers, I find the DSA to be inconsistent. The two-stage feature really isn't perceptible. I usually just feel one stage of heavy creep, and it eventually lets go. Sometimes there is no creep and it just "breaks" when I put moderate pressure on the trigger. I actually have a couple of these. Both have noticable overtravel. One is noticably better than the other, but still nothing to write home about.

The FSE seems to be the opposite. I can very much feel the two stages. In fact it feels almost like three stages (reminds me of the "match" trigger on a Bushmaster). The first stage is light and springy. I can feel consistent creep in the second stage. The trigger then seems to "bottom out," requiring a good bit more pressure. Then, without further perceptible movement, it breaks. But, at least it is consistent. It has absolutely no perceptible overtravel.

I've been able to live-fire one of the DSA's quite a bit. The FSE has only seen dry-fire duty. The FSE and the better DSA will get some live-fire testing in 47 hours.

[ September 20, 2001: Message edited by: gary.jeter ]

usmc326
September 20, 2001, 09:25
Yanky: We all have made posts we regret. I was surprised a bit myself at the responses you got, as no one here normally pulls your leg unless you're an old hand.
I think alot of people are "losing it"
over stuff that wouldn't ordinarily bother them, since 9-11-01. The second by second coverage on every channel sure doesn't help. Everybody is tired, stressed, unsure what to say, etc., wondering about the next attack, or if
our retaliating will trigger a Jihad,
with no end in sight.
Keep busy & build some awesome FAL's,
and prove they have a sporting use this Fall. 2-3 yrs. ago guys used to post their deer and elk photos, with the FAL prominently featured. I'd like to see that tradition return.
Lighten up everyone...we'll give Bill an "atomic wedgie" when he resurfaces. ;)

ByronF
September 20, 2001, 09:39
Originally posted by usmc326:
<STRONG>we'll give Bill an "atomic wedgie" when he resurfaces. ;)</STRONG>

I dunno...you have to have SOME slack in the waistband to give an ATOMIC wedgie.

yankytrash
September 22, 2001, 10:22
Happy to report my problem is fixed with no parts replacement.

Just to share my results, here's what I did:

With a file, I ground off 1/32" off of each notch face on the hammer. I used the stone descibed below to VERY gently softened the bottom edge of the notch where it disengages form the trigger sear, to help with the rouhg trigger pull I had before. (Happy to report THAT was a success, too, but it is not for the faint of heart -you can potentially ruin the hammer with only one extra stonestroke)

On the trigger sear, I filed just a tad (again, 1/32") of the forward angle off the forward tip.

To do a preliminary dry-fire test of my results, I cocked the gun and slammed the butt to the floor repeatedly. I also slammed my fist as hard as I could to the rear of the handgaurd repeatedly. When it stopped misfiring, I stopped and brought to the range (with my file and stones in my pocket).

As suggested to me by floatingFAL, I finished off the damage with my 70's generation USMC knife sharpening stone.
Those measurements were purely luck of the draw, and your results may vary - don't use a file, use a stone.

As with any gun fix, use common sense and be honest with yourself. Can you handle machine-work, are you mechanically inclined, and do you completely understand the problem you are about to attempt to fix? Only you know the answer, and if you are, at the least bit, unsure of yourself, go to a smith.

Good Luck.

TooTech
September 22, 2001, 14:33
Hey Yanky,

How's the trigger pull after all that work?

yankytrash
September 25, 2001, 04:16
Trigger pull is beautiful now. I used to have a hard spot after the slack was pulled from the trigger. Now, for all intensive purposes, it's one smooth motion. The first pull of the trigger was so smooth, I actually thought it fired out of battery again - until I made a conscience effort to feel the amont of trigger pull.

I blame that cure on the filing/honing of the forward face of the hammer notch (when the gun is cocked).

How long will it last? I don't know. I have the 'new' h/t/s set ready to drop in if/when it does wear out and goes back to a firing-out-of-battery condition. My feeling is that these parts can only be honed so many times before permanent damage is done, but I'll enjoy the competition-like trigger pull I have for now.

I plan to run this sucker rampit with about 400-500 rounds this weekend. That should determine if this is a permanent fix or just putting off the inevitable.


I guess the FAL's trigger pull can only really be described in terms of 'smoothness', as opposed to pounds of pressure. Too many springs and synchronizations going on in the bolt action to get messin with the actual weight of the trigger pull.
I thought of maybe cutting a loop or so off the trigger spring, but stopped myself when I realized it would only bring back the rough secondary stage of the trigger pull. I like what I have now - and if it ain't broke, don't fix it.
;)

[ September 25, 2001: Message edited by: yankytrash ]