Light trigger can cause AD?

[curt]

Recently i saw a post that cautioned about using reduce trigger plunger springs. I thought that the post was here but danged if i can find it so i'll just post a new thread.

The concern was that with a reduced plunger spring that if the rifle was struck on the ground butt first with the bolt held back by the BHO, that the bolt would go forward and that the hammer would follow. since i've reduced the pulls on two of my fals i thought i'd give it a try.

FAL #1 is a 18 inch lightweight carbine with a pull that averages 4lb 14 oz with a crisp break. bolt went forward hammer did not follow.

FAL 2 is a 20 inch STG kit with a 4lb 6 oz pull. bolt went forward and with the safety off the hammer followed, with the safety on it did not.

What this means i'm not sure. The poster that i can't remember implied there might be circumstances where one might drop a FAL with the bolt held back and have a discharge. I don't have any primed cases around or i would have tried them to see if the following hammer would cause discharge. Even if it did i'm not sure it is a problem as no BHO will hold a bolt on any of the guns, garand/ar/m1a etc, i have and dropping a loaded gun with the safety off is generally considered a bad idea.

any thoughts?

[NewtoFals]

That was me that posted about that. I replaced the trigger plunger spring and fixed the problem. I figured that a bit heavier trigger is a better trade off than a hole in my melon. Problem was that just setting the rifle down just a little bit hard would cause the hammer to go forward.....problem isn't the bolt hold open. I do not like to handle weapons that are that delicate. Yes dropping a loaded rifle isn't recommended but who's to say that it won't fall when you lean it against a table or what not. The safety will NOT keep the hammer from going forward in a some cases.

To me it just wasn't worth having a lighter pull and sacrificing safety.


I recommend replacing both trigger and sear springs unless it's obvious that the hammer to sear engagement surfaces aren't right. If your trigger group is FSE in the 'unsafe' rifle you might want to see if they are marked MO2 if they are they might be defective.....does the rifle double at all? I had an FSE mo2 sear that was too short causing it to double after 280 rounds. FWIW on i had fired many rounds in the rifle that had the weak trigger spring and i pretty much found out that the hammer would go forward by accident when tapped on the ground.

SAFETY FIRST!!!!!!!!!!!!

[Radio]

"The safety will NOT keep the hammer from going forward in a some cases."

This might be a slight typing error, but the truth is, THE SAFETY WILL NOT KEEP THE HAMMER FROM GOING FORWARD IN ANY CASES!!

The "safety" on an FAL is nothing more than a trigger block. The only thing keeping the hammer from going forward if cocked is the sear engagement in the hammer notch. Keep THAT in mind the next time you try a trigger job on your FAL.

If any rifle has a hammer follow problem, either you have a bad h/t/s or you have tweaked the springs too much. Many builders have reported problems when reducing the trigger return spring under four pounds, or getting the trigger return spring and sear spring too far out of balance.

--Radio

[ByronF]

What Radio said. Does the safety block sear movement at all? Can't recall. But it certainly doesn't hold the hammer back. Light hammer-sear engagement on an FAL is not worth the danger.

Byron

[cliffy109]

Would somebody explain to me how a lighter than spec trigger return spring could allow the hammer to fall in the above described situation? I certainly could be missing something here, but it would seem to me that the trigger return spring only affects the resetting of the trigger. If the hammer followed the bolt when dropped due to a light trigger return spring, wouldn't it do the same thing when fired intentionally?

Further, if the above described situation happened and the rifle fired, wouldn't that mean you could make a full auto by doing nothing more than replacing the trigger retun spring? Obviously not, but I would like a few more details on this.

[curt]

Okay so maybe i didn't remember newtofals post correctly. The test i did was with the bolt held back by the BHO, when FAL2 was dropped i got hammer follow. However, with the bolt forward, not held back, i don't get hammer drop with the safety off and banging the butt. So i guess i don't have a problem?

I agree cliffy that if you're relying on your return spring to prevent a AD then you're in trouble. I think that what is happening with FAL 2 is that maybe the engagement is towards the min side and the jarring from the bangin AND the bolt slamming is sufficient to dislodge it.

FWIW i did not reduce the engagement, i took out some of the tool marks on the sear with a stone and hit it with a polishing buff. HTS was the latest from FSE, i think they are M10?

I likes my triggers.

[Radio]

There is a little confusion here because we are talking about several things at once.

* Bolt Hold Open: This has NOTHING to do with your hammer/trigger/sear. If you have a good engagement between the bolt and the BHO, the bolt will usually remain open even in case the rifle is jarred (up to a point). If you have a less-than-good BHO surface or bolt surface and this marriage is NOT a good one, the bolt can be jarred forward. That's it.

* Trigger Return Spring: This will affect whether your trigger re-sets, not whether the hammer falls prematurely. Don't confuse this with the...

* Sear Spring: This will affect whether, or how positively, the sear engages the notch on the hammer. If this spring is too heavy, it will take a bear of a trigger pull to force the sear out of the hammer notch; if too light, the sear may only partially engage the notch... or be overpowered by the hammer return spring and not engage at all.

The problem with modifying these springs out of their designed relationships is that you create for yourself a rather grim trigger pull, AND/OR you reduce the safety and reliability of your sear engagement. The trick is to follow the advice of experienced gunsmiths who have blazed these trails already and KNOW what spring strengths work.

* Full-Auto Conversion: I saved this for last because of its complexity. First: You are NOT going to be able to do this by replacing or tweaking a spring. You absolutely will need a sear-cut receiver (you don't have one) and a safety sear (you can't use this part), period. This is STRICTLY illegal unless you already own a pre-86 machine gun, or are licensed to manufacture post-samples. Or you're a government agency. A falling hammer won't make your rifle go full-auto, anyway.

In the FAL design, the bolt locks into battery while the carrier is still moving forward; thus the firing pin is blocked by the carrier briefly. This was to allow time for the carrier to trip the safety sear, which controlled the hammer. Originally, it was the safety sear which released the hammer, whether in semi-auto or full-auto operation.

In full-auto, the trigger is pulled once and held back; this forces the nose of the "regular" sear down and away from the sear notch at the rear of the hammer, preventing it from engaging the hammer; ONLY the safety sear holds and releases the hammer from its notch in the front. In semi-auto, the trigger is not depressed as far, which allows the "regular" sear to engage the hammer FIRST before the safety sear engages the front notch; then, when the bolt trips the safety sear, the hammer is STILL held in place by the "regular" sear, until the trigger re-sets and is pulled again.

The "safety" factor came into play as the hammer was held by the safety sear UNTIL the carrier was fully forward and had unshrouded the firing pin; thus the safety sear had more than just the simple function of operating the rifle in full-auto. It is a testimony to the greatness of the FAL design that it still functions well even WITHOUT the safety sear.

Because the carrier is blocking the firing pin UNTIL the rifle is fully in battery, it is usually very difficult to get an FAL to fire OUT of battery. Also, a rebounding hammer will normally expend much of its energy on the carrier, usually leaving insufficient force when striking the firing pin to fire a round (though it might dimple the primer). ADs are more likely with softer, commercial primers, but still less frequent in an FAL than in many other rifle designs.

It is late and I am wiped out. Hope this has made some sense to you.

--Radio

[cliffy109]

You can relax Radio. I assume you were referring to my post. You must have been tired the first time you read it. Go back and take a look. I indicated that I am well aware that one can not convert to full auto by the replacement of the trigger spring. I was pointing out that if the gun could fire when the bolt slammed forward without pulling the trigger, this situation would also create a full auto rifle. This, of course, is not what is really happeneing, especially not as a result of replacing the trigger return spring.

[elbo]

Originally posted by Radio
* It is late and I am wiped out. Hope this has made some sense to you.

There's so much wrong with this that I don't have time at lunch to sort it out.

[Radio]

I had just travelled 400 miles in 100+ degree heat with no air conditioning in my Suburban. I drank over 1.5 gallons of water and went to the bathroom only once all day. Now I have had some decent sleep and feel a little more clear-headed.

cliffy109: I saw your "obviously not"; stand down, sir. I was not addressing you personally but rather the many others who cruise the Files and have these questions, heaven knows they ask these things often enough. I also agree with you that replacing the trigger return spring is NOT the problem as described.

Hammers will fly forward because the sear didn't hold it back. The sear didn't hold it back because something is wrong with the physical engagement between the two (badly machined parts or improper tweaking by the builder) or because a too-weak sear spring caused the sear to only partially catch the hammer in the sear notch. Either case makes the assembly susceptible to disengagement during jarring, by the whacking of the bolt as released by the BHO, or the banging of the rifle butt against the ground/etc, or both, or ANY sufficient blow to the rifle.

I trust this helps elbo with my admittedly incomplete post of last night. Sorry I wasn't more articulate, though I don't claim to be an expert in any case. I look forward to any clarifications you can add.

--Radio

[curt]

Radio, i'm not sure i'm following, or maybe that you're following . FAL #2 does not drop the hammer with the bolt closed and safety off even with vigourous buttstocks against the carpeted floor. If i did not have sufficient sear engagement it seems to me that the hammer would drop.
It will however, allow the hammer to follow the bolt if the same thing is done with the bolt held back by the BHO.

I disagree that the fact that the BHO won't hold the bolt while buttstocking the ground is a problem. Since most rifle BHOs that i'm familiar with are spring loaded to release the bolt all it takes is a moment of letup of the bolt's preasure against the BHO to release it. In fact that is what is supposed to happen. you pull back on the bolt to release preasure and if the mag follower is not pressing the BHO, the bolt drops.

[elbo]

Originally posted by curt
I disagree that the fact that the BHO won't hold the bolt while buttstocking the ground is a problem. Since most rifle BHOs that i'm familiar with are spring loaded to release the bolt all it takes is a moment of letup of the bolt's preasure against the BHO to release it. In fact that is what is supposed to happen. you pull back on the bolt to release preasure and if the mag follower is not pressing the BHO, the bolt drops.

Yes, FALs and ARs. Used to be quite a game in basic training, kick the rifle slung on the shoulder in front of you and attract him some attention.

But like Radio says the only thing that should release the hammer is a pull of the trigger. Weak springs and miscut faces can let the sear slip off of the hammer. Miscut faces with weak springs 90% cause, badly miscut faces won't need weak springs.

My Unified Theory:
The sear spring has little to do with the trigger weight, it should be as heavy a spring as you can install.
As you pull the trigger the sear is to the rear on the trigger pin, the hammer spring has pushed it back. The shelf on the rear of the trigger is pushing the tail of the sear up, sliding the nose down off of the hammer. When the two surfaces have cleared each other they move in opposite directions. The sear spring causes the sear to jump forward and the hammer spring causes the hammer notch to rotate back and up.
The jump forward allowed the tail of the sear to fit below the trigger shelf so the nose can raise enough to recatch the hammer(semi only, in AUTO the trigger moves the sear further and catching the hammer is left to the safety sear).
The limits on the spring weight are, the hammer spring must compress it and the trigger spring must be able to pop the sear back over the shelf.

[curt]

Originally posted by elbo

Yes, FALs and ARs.

And M1As and M1 carbines as well. Yeah elbo i don't find anything about your theory to disagree about. Note: the only spring i changed to get these triggers was the trigger return plunger spring which i substituted a sear spring for.

Anyway i don't think i have a AD problem which was my first concern.

[xcpd69]

* Bolt Hold Open: This has NOTHING to do with your hammer/trigger/sear. If you have a good engagement between the bolt and the BHO, the bolt will usually remain open even in case the rifle is jarred (up to a point).

Up to a point.

When you "jar" a rifle by striking the butt on the ground, or a hard surface, the sudden stop of the rifle causes the bolt to continue downwards, against the recoil springs, from inertia. Once this happens, the BHO is retracted by it's spring, as the pressure from the bolt on it is released. The bolt, once the rearward movement is stopped by the compression of the recoil springs, is now driven back forward and with the BHO no longer in place, slams home.

No malfunction, just simple physics.

I have a "Smilie Face" scar on the tip of my left index finger, from a practical demonstration of this phenomenon, combined with a dose of stupidity.

[elbo]

Originally posted by xcpd69

1. simple physics.
2. "Smilie Face"scar
3. practical demonstration

Contradictory oxymorons


1. You havn't read Steven Hawking. (he has a 'Big Bang' theory too)
2. I've never had an experience leave a scar and a smile. (sober)
3. Did it feel practical? (right up to the end I'll bet)

I do admire your dedication. Nothing makes a lesson stick with a student like being splashed with blood.

[xcpd69]

Originally posted by elbo


Contradictory oxymorons


1. You havn't read Steven Hawking. (he has a 'Big Bang' theory too)
2. I've never had an experience leave a scar and a smile. (sober)
3. Did it feel practical? (right up to the end I'll bet)

I do admire your dedication. Nothing makes a lesson stick with a student like being splashed with blood.

OK, I'll tell the whole story, from a post in 2001, funny in retrospective. Not so funny at the time:

YOU MIGHT BE A WECSOGER IF YOU GET FAL FINGER INSTEAD OF M-1 THUMB

Or "Bolt hold open latches...DON'T."

Or never try to diagnose why your gas piston is slightly sticking, by removing the dust cover, locking the bolt back, putting the piston(minus the spring) in the gas tube, and then moving it up and down to see where it sticks, by pushing the protruding end up and down with the tip of your left index finger, while holding the rifle in your right hand. And when it inevitably sticks, NEVER gently try bouncing the butt of the rifle on the floor to unstick it.

Remember, "bolt hold open latches...DON'T" especially when rifle is bounced on floor lightly.

If you have ignored all the above, you now have blown the end out of your left index finger, which is still shut in the action, and hopefully your right hand is still holding the rifle, leaving you with the interesting problem of retracting the bolt without the use of a third hand, or dropping the rifle.

Carefully set the butt of the rifle on the floor, and grasp the rifle with the remaining fingers(if any) of the left hand, then reach around and retract the bolt with the right, freeing what is left of your finger.

Set the rifle aside, and go to the bathroom and staunch the bleeding, and apply first aid, and bandaging. Then go back and clean all traces of blood from the rifle, before it damages the finish. Hopefully you'll get this done before the finger starts to REALLY throb.

You might consider going to the emergency room, especially if any bone shows through. Mine didn't, but when I finally went to the doc two days later, he said I probably should have had 3 stitches, but by now it was two late. It took about two weeks to heal. I now have a "happy face smile" on the tip of my finger.

Needless to say I won't repeat that stupid stunt. I'll think up something equally stupid.

__________________

[Radio]

My "something equally stupid" was an attempt to remove a stuck dust cover... simply WOULDN'T come off from the back... by sticking my fingers in the ejection port and trying to PUSH it off instead of PULL it off.

The ejector left a deep, bloody gash in three of my fingers. Took a LONG time for those scars to disappear. Since they have, I guess that's a "horseback" way of supposing they weren't deep enough to require stitches.

Since then I've used properly padded vice-grips in similar situations.

On the BHO, "up to a point" means just that, and not an attempt to ignore physics. What I was referring to are the "touchy" BHO/bolt combos that disengage just by breathing on them. Although, for what it's worth, my Type-II DSA has a somewhat "sticky" BHO that darned well keeps that bolt retracted until I darned well pull the BHO down. I got to actually like it before I had time to correct it.

--Radio

[elbo]

Originally posted by xcpd69
OK, I'll tell the whole story, from a post in 2001, funny in retrospective. Not so funny at the time:

Always funnier when it doesn't happen to me.
I thought a FAL finger something else. Good thing it wasn't THAT finger as a "happy face smile" there would be very confusing.
Like on the back of some trucks, DODGE RAM. I always dodge.

I've never cut myself using a rifle. Mostly Exactos and a Beretta .25 once.
Two grooves across my left thumb. Two hand holds don't always make you more accurate. Sometimes they make you pack up and go home.

[xcpd69]

Originally posted by elbo
I've never cut myself using a rifle. Mostly Exactos and a Beretta .25 once.
Two grooves across my left thumb. Two hand holds don't always make you more accurate. Sometimes they make you pack up and go home.

My dearly beloved, once did the same thing with her then current pistol. A Beretta 70S in 22lr.

We were at an indoor range, and I was helping her familiarize herself with the Beretta. Showed her the two handed hold, which she promptly screwed up by placing the thumb of her off hand, across the web of the shooting hand.

I stopped her before she could fire, and warned her to move her thumb, as the slide coming back would hit it. Corrected, she proceded to shoot at the target. Satisfied, I turned to my own pistol, and after a few shots, realized I needed to adjust the rear sight, and had forgotten my screwdriver. Seeing she was doing OK, I stepped out for a bit to borrow a screwdriver. Gone maybe 2 minutes.

When I stepped back in, she was holding her hand, and the pistol was down on the table.

Railroad tracks across her left thumb. Sigh.....

No major damage, but she had it impressed upon her that the off hand thumb does NOT go behind the slide on a semi-auto. In a way that was remembered far better, than my words of warning that day.

[elbo]

I would have been safer in front of the gun.
Seeing blood always helps the memory. Thankfully I had no witnesses.