I really like the JP trigger but it can be adjusted down to the 'nth degree. Which I did a little too much. So after about 30-40 rounds it went full auto!!!    Surprised the you know what out of me!!!

More reasons for the 5rnd mag limit.

More reasons for the 5rnd mag limit.

I would prefer to empty a 30 round mag full auto. 

I was not going to get into too much detail, but since we are discussing it....

SNIP

Thank you for going into that!  Always good information.   

While you may be "new" to ARs, I bet you've seen quite a lot with the frequency you shoot and with your buddies.  While I have shot thousands of rounds, my guns are pretty vanilla.  I'm not really into mods, particularly triggers and I shoot only factory ammo.  That eliminates, or at least reduces a number of "variable gremlins".  I have shooting buddies who absolutely LOVE to tweak this, or tweak that.  One in particular also reloads and loves to tweak stuff there as well.  Well, shooting matches and in training, he was getting various malfunctions.  One was eventually found to be too light a trigger spring, but that took a bunch of my factory ammo to rule out primer issues on his reloads.  Then his homemade holsters were hitting the mag release, so the mag would unseat upon draw or even come flying out of the gun on the draw.  It was actually kind of funny at times to see the mag go flying out.  I mean, I mostly don't mess with that stuff due to time and I definitely don't look down on him for his experimentations.  Just that I've also some to realize that with that experimentation comes a lot of troubleshooting and doubt entering into the equation. 

Thank you for going into that!  Always good information.   

While you may be "new" to ARs, I bet you've seen quite a lot with the frequency you shoot and with your buddies.  While I have shot thousands of rounds, my guns are pretty vanilla.  I'm not really into mods, particularly triggers and I shoot only factory ammo.  That eliminates, or at least reduces a number of "variable gremlins".  I have shooting buddies who absolutely LOVE to tweak this, or tweak that.  One in particular also reloads and loves to tweak stuff there as well.  Well, shooting matches and in training, he was getting various malfunctions.  One was eventually found to be too light a trigger spring, but that took a bunch of my factory ammo to rule out primer issues on his reloads.  Then his homemade holsters were hitting the mag release, so the mag would unseat upon draw or even come flying out of the gun on the draw.  It was actually kind of funny at times to see the mag go flying out.  I mean, I mostly don't mess with that stuff due to time and I definitely don't look down on him for his experimentations.  Just that I've also some to realize that with that experimentation comes a lot of troubleshooting and doubt entering into the equation.

I have had steadfast rule for myself over the years. And that is that I can mod/tweak whatever on any gun in my collection except my self defense gun(s). In which case I use only factory ammo and a stock (unmolested) revolver. I test the two every couple of years and rotate in new ammo. In my mind this combination is about as reliable, maintenance free and as a repeatable combination there is.

As far as the mag popping out, I have modded my Glock with an extended mag release so I don't have to reposition the gun in my hand in order to drop a mag. And it works in my holster just fine. My problem came about when I first got it I would shoot with my thumb touching the side of the mag release. And while shooting the mag would just mysteriously drop out. At first I thought I had adjusted it so the mag was not held in securely under fire. But after a little testing I found it was due to operator error. 

Variation #1 - Click of breaking of trigger - bang - still holding trigger to rear - release trigger - bang (does the second bang occur on the reset?)
Variation #2 - Click of breaking of trigger - bang & bang - still holding trigger to rear - release trigger - dead trigger (bolt is forward, but hammer is not cocked?)

I would say 1 but can't rule out 2 based of my recollection of events. Usually 1 happens and I have to recock the next round by pulling back the charging handle a bit without ejecting the next round.

It's difficult to determine which in Johnny's video because he's filming at 30 fps and the slam fire can happen between frames.

I'll play with it Thursday using ren's plan. If it happens with the PMC ammo, then I'll reinstall the stiffer trigger spring. If it happens with the Fed primers I previously loaded, then I'll switch to CCI 400 or something.

I very much appreciate all of the advice.

Then his homemade holsters were hitting the mag release, so the mag would unseat upon draw or even come flying out of the gun on the draw.  It was actually kind of funny at times to see the mag go flying out. 

That's an old cliche in many comedy western movies but never thought it could actually happen.

If you say that you have to recock the hammer after the double, then I would say you may have a problem with sear engagement.

Wouldn't rule out soft fed primers. They are known to have issues in ARs.

Maybe, (rifle completely unloaded pointed in a safe direction no ammo anywhere around, yadayada) you could cycle it by hand, letting the bolt slam home, and see if the trigger resets every time, or if the hammer falls home without you re-pulling the trigger, to see if your hammer is falling off the sear?


Maybe check carefully down in the trigger group, to see if there is any crud or burrs that might be effecting proper function?

If you say that you have to recock the hammer after the double, then I would say you may have a problem with sear engagement.
Wouldn't rule out soft fed primers. They are known to have issues in ARs.
Maybe, (rifle completely unloaded pointed in a safe direction no ammo anywhere around, yadayada) you could cycle it by hand, letting the bolt slam home, and see if the trigger resets every time, or if the hammer falls home without you re-pulling the trigger, to see if your hammer is falling off the sear?
Maybe check carefully down in the trigger group, to see if there is any crud or burrs that might be effecting proper function?

Appreciate the advice. I haven't had any issues with the trigger except during the slam fires. It's all cleaned out. My guess is that it's a combination of light trigger spring and soft primer. I'll find out Thursday at the range. I plan to be there early to set up my new chrono.

I have had steadfast rule for myself over the years. And that is that I can mod/tweak whatever on any gun in my collection except my self defense gun(s). In which case I use only factory ammo and a stock (unmolested) revolver. I test the two every couple of years and rotate in new ammo. In my mind this combination is about as reliable, maintenance free and as a repeatable combination there is.

As far as the mag popping out, I have modded my Glock with an extended mag release so I don't have to reposition the gun in my hand in order to drop a mag. And it works in my holster just fine. My problem came about when I first got it I would shoot with my thumb touching the side of the mag release. And while shooting the mag would just mysteriously drop out. At first I thought I had adjusted it so the mag was not held in securely under fire. But after a little testing I found it was due to operator error. 

For guns for defense, I'm pretty close to the same.  I've done minor tweaks on my Glock 17s.  Sights, mag release, and slide stop. They have a grip plug, but I could do without those.  I've played around with the disconnect on my Glock 34, but that's pretty much only for competition.  Not sure I like that enough where I would consider changing on my 17s.  For the most part, I tend to stay away from trigger stuff on defensive guns, including my ARs.  Reliability is the main consideration here and I am more concerned that my "bubba'ing" of stuff will have things malfunctioning like my "mod happy" shooting friend.  I tend to not like having more questions when I am at the range. 

I've seen people inadvertently have their thumbs on the slide stop/release, but not the mag release.  You must be special.   

I've seen people inadvertently have their thumbs on the slide stop/release, but not the mag release.  You must be special.   

I have long fingers. I'll let you infer whatever you want from that... 

I have long fingers. I'll let you infer whatever you want from that... 

That you're trying to justify why your "tools" feel smaller in your hands???

 

Appreciate the advice. I haven't had any issues with the trigger except during the slam fires. It's all cleaned out. My guess is that it's a combination of light trigger spring and soft primer. I'll find out Thursday at the range. I plan to be there early to set up my new chrono.

you have to isolate the problem. It is either the trigger or the ammo.

That you're trying to justify why your "tools" feel smaller in your hands???

 

Due to the large frame size of my "tools" it takes two very large hands to get a grip on them properly. 

Due to the large frame size of my "tools" it takes two very large hands to get a grip on them properly. 

....
This thread is about bump firing.....oh wait....never mind

....
This thread is about bump firing.....oh wait....never mind

Accidental discharge. . . 

If you say that you have to recock the hammer after the double, then I would say you may have a problem with sear engagement.

Wouldn't rule out soft fed primers. They are known to have issues in ARs.

Maybe, (rifle completely unloaded pointed in a safe direction no ammo anywhere around, yadayada) you could cycle it by hand, letting the bolt slam home, and see if the trigger resets every time, or if the hammer falls home without you re-pulling the trigger, to see if your hammer is falling off the sear?


Maybe check carefully down in the trigger group, to see if there is any crud or burrs that might be effecting proper function?

I agree with Heavies.  i think your double fire issue is a result of either a malfunctioning disconnector, or inadequate trigger/hammer engagement surface area or tension.

did you install one of those grip screws that push up on the trigger bar?  like this:  https://www.joeboboutfitters.com/JoeBob_s_AR15_Grip_Screw_Trigger_Adjuster_p/jb-triggeradjuster.htm

when you shoot, do you normally do a full trigger follow through and then wait for the full trigger reset? or do you have a tendency to slap the trigger?

if the two questions above don't resolve your issue, then i suspect that you're getting hammer follow due to inadequate trigger/hammer engagement surface area or tension.

what kind of trigger do you have?

Can you check the springs on the trigger?  This guy has a similar issue as you.  Info on trigger spring starts at about 5:00m.

https://youtu.be/L50Mj3XTD-w?t=5m

He kinda rambles..  lol

Someone commented that if the hammer spring is not strong enough, it can cause the hammer to bounce off the disconnector, instead of the disconnector catching it, causing the rifle to double or even worse.

I agree with Heavies.  i think your double fire issue is a result of either a malfunctioning disconnector, or inadequate trigger/hammer engagement surface area or tension.
did you install one of those grip screws that push up on the trigger bar?  like this:  https://www.joeboboutfitters.com/JoeBob_s_AR15_Grip_Screw_Trigger_Adjuster_p/jb-triggeradjuster.htm
when you shoot, do you normally do a full trigger follow through and then wait for the full trigger reset? or do you have a tendency to slap the trigger?
if the two questions above don't resolve your issue, then i suspect that you're getting hammer follow due to inadequate trigger/hammer engagement surface area or tension.

I installed the grip screw but removed it. I pull then wait. It doesn't usually happen immediately afterwards. More like when I start to reset the trigger.

Anyways, I decided that the slam fire problems were with my trigger. I shot the PMC Bronze ammo and had a few slam fires, so it's probably not just the Federal primers. Interestingly, I only had two slam fires out of the 100 rounds of TAC and Fed primers I shot. I plan to replace the trigger soft springs I installed with the stock springs and see if the problem goes away.

I plan to replace the trigger soft springs I installed with the stock springs and see if the problem goes away.

I had the opposite issue with a .308 build.  Went soft on trigger springs and the thing would not reliably fire NATO surplus.  Had to go back to heavy stock springs.