Trigger slap questions

[Bill Bryant]

1) Have you ever encountered an AR with trigger slap?

2) What part(s) would have to be out of spec to cause this?

3) In what way would the parts have to be out of spec? Too big? Too small? Too much or too little metal where?

[Bill Bryant]

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[C4IGrant]

1) Have you ever encountered an AR with trigger slap?

2) What part(s) would have to be out of spec to cause this?

3) In what way would the parts have to be out of spec? Too big? Too small? Too much or too little metal where?

I am not sure that "trigger slap" is the correct term.

What is the trigger doing?

Trigger slap generally means that the user is coming off the trigger and then re-engaging it (instead of just leaving their finger on the trigger).



C4

[BufordTJustice]

Do you mean trigger slap as in AKM/AK47 trigger slap? I have never heard of this in an AR, tho I suppose it's possible. Time to see a gunsmith if you suspect this is happening.

[Bill Bryant]

I am not sure that "trigger slap" is the correct term.

What is the trigger doing?

Trigger slap generally means that the user is coming off the trigger and then re-engaging it (instead of just leaving their finger on the trigger).



C4I used "trigger slap" to mean a fault in a fire control mechanism that transfers enough energy back through the system from the bolt carrier that it "slaps" the finger and makes it sting. I've seen a couple of comments here and there in reference to ARs, suggesting that this can happen if lower parts aren't to spec.

The trigger isn't doing anything at this point. I'm building up a carbine from parts. So far I have only a completed lower (Stag lower receiver, Stag/CMT LPK) so I can't test anything.

My question comes as a result of my study of the fire control system and my curiosity about what makes safe/fire selectors impossible to insert after the FCG is installed in some lower receivers and what makes them go in just fine in others. There was an earlier thread about this (https://www.m4carbine.net/showthread.php?t=19126) that got me to thinking about what this difference could do if it got too severe (tolerance stacking)--if the recoiling hammer had to move not just the disconnector but the trigger as well in order to engage the disconnector.

I'm new to the AR world but not new to the engineering and repair of complicated mechanisms.

(I'm typing all of this at my desk while students do homework. Hope it makes sense. I'll write more tonight.)

[Bill Bryant]

Do you mean trigger slap as in AKM/AK47 trigger slap? Yes, that's what I mean.

[Bill Bryant]

Here's a reference to "trigger slap."

http://www.interpolsolutions.com/catalog.php?category=AR-15%2FM-16%20Internal%20Parts

[BufordTJustice]

Yes, that's what I mean.

In the AK mechanism, it's usually the overly-long 'tail' of the disconnector that is pushed down against the trigger shelf by the hammer and/or bolt carrier coming into pre-mature contact with it during the cocking of the mechanism. I'm not familiar enough with the AR fire control group yet to point you to some corresponding parts. Maybe a call/email to Bill Springfield, Jard, or Timney is in order?

On a side note, what class are you instructing? I'm always happy to see people in the education profession who have an interest in firearms. As with many of today's workplaces, schools/universities are a place of near-phobia toward firearms. Good for you. :)

[C4IGrant]

I used "trigger slap" to mean a fault in a fire control mechanism that transfers enough energy back through the system from the bolt carrier that it "slaps" the finger and makes it sting. I've seen a couple of comments here and there in reference to ARs, suggesting that this can happen if lower parts aren't to spec.

The trigger isn't doing anything at this point. I'm building up a carbine from parts. So far I have only a completed lower (Stag lower receiver, Stag/CMT LPK) so I can't test anything.

My question comes as a result of my study of the fire control system and my curiosity about what makes safe/fire selectors impossible to insert after the FCG is installed in some lower receivers and what makes them go in just fine in others. There was an earlier thread about this (https://www.m4carbine.net/showthread.php?t=19126) that got me to thinking about what this difference could do if it got too severe (tolerance stacking)--if the recoiling hammer had to move not just the disconnector but the trigger as well in order to engage the disconnector.

I'm new to the AR world but not new to the engineering and repair of complicated mechanisms.

(I'm typing all of this at my desk while students do homework. Hope it makes sense. I'll write more tonight.)

To date, I have never had happen to me what you are describing and have also never known anyone have this issue.

So I would not worry about it.


C4

[m4fun]

I have experience this and know this is common "only" in 9mm M16s/ARs.

This happens due to the lack of ramping of the 9mm BCGs(one unit for 9mms) As with the firing of a round, the BCG is forced back via blowback(as opposed to DI) Now, without ramping, the hammer is not pushed back gracefully as with all the M16 and varying AR15 BCs. It is pushed down sharply(more sharply than normal) and the push on the trigger can really suck. Disconnector has nothing to do with this as I've done this on full auto. Ouch!

Solution is to have your BCG ramped to match the angle of an M16 BC. Side note is that this stress on the hammer also can cause "egging" out of the hammer pin and even trigger pin holes on your receiver. This really has created quite a market for not just rampling of 9mm BCGs, but KNS pins as well. All cheap insurance for you $$$ registerd receiver.

[Blankwaffe]

We had a similar issue to the "trigger slap" on some Armalite M15A2's with notched hammers and ramped carriers back around 2000.
The sting to the finger was traced to the notched hammers being out of spec(I personally suspected the gutted carriers as well) and was hanging the spool of the AR15 firing pin with unshrouded carriers.
Evidence was bent FPRP and chewed AR15 firing pin spools with a service life of 400 rounds or less.The condition worsened as the ramped carriers wore and peened at the ramp eventually leading to locking the weapon.One rifle was so bad that the hammer actually sheared a new FPRP in less than 100 rounds and ejected the firing pin.The trigger would sting the finger just as "trigger slap" would be described in some of the Tapco AK FCG threads a couple years ago.
Fast fix was to install a shrouded carrier which solved the issues altogether.Later the FCG was changed to a quality set.

[hillmillenia]

Yes I have experienced trigger slap in an M4 build I put together. I swapped out the FCG for another brand and everything thing works fine. I susposed I could have started filing and polishing but I'm not a good enough smith for that. And yes slap will give you a sore trigger finger just like the Romanain SAR's did back when...

[Bill Bryant]

Yes I have experienced trigger slap in an M4 build I put together. I swapped out the FCG for another brand and everything thing works fine. I susposed I could have started filing and polishing but I'm not a good enough smith for that. And yes slap will give you a sore trigger finger just like the Romanain SAR's did back when...
If you don't mind saying, what FCG gave you a problem, and what FCG fixed it? Also, if you happened to notice, did the problem FCG also prevent you from installing the selector after it was installed?

[hillmillenia]

Bill,
The parts that gave me a problem were CMT and I don't really know if it was the trigger, the disconnector or even possibly the hammer. I messed with it for quite some time. I had never had any problem with builds before, but as I said, I'm no smith. I can slap the parts together and if they're spec, they always worked. If I have to start fitting parts...filing and polishing, well...As to your question, I didn't have any problem with the selector after the other parts were in. Someone on arfcom suggested it was the disconnector "tail" and another recommended filing the hammer down though I don't know why that would have any effect on slap...mabey the carrier running over it. Either way I replaced only the trigger, disc and hammer with RRA parts and no problem since. I think CMT makes a good part, Just gotta bad one.

[Bill Bryant]

Bill,
The parts that gave me a problem were CMT and I don't really know if it was the trigger, the disconnector or even possibly the hammer. I messed with it for quite some time. I had never had any problem with builds before, but as I said, I'm no smith. I can slap the parts together and if they're spec, they always worked. If I have to start fitting parts...filing and polishing, well...As to your question, I didn't have any problem with the selector after the other parts were in. Someone on arfcom suggested it was the disconnector "tail" and another recommended filing the hammer down though I don't know why that would have any effect on slap...mabey the carrier running over it. Either way I replaced only the trigger, disc and hammer with RRA parts and no problem since. I think CMT makes a good part, Just gotta bad one.
I wish I could see pictures of the parts that caused you trouble.

[hillmillenia]

I sold the parts to someone with more ability than me. Well he hasn't complained anyhow :) Here's a link to the complete rifle.
http://m4carbine.net/showthread.php?p=450991#post450991