Had a double fire at the range today.

[CZB1962]

I just built an AR in 7.62x39 and it was finally nice enough to go try it out today. Everything was going super well until my son was shooting and all of the sudden bam,bam....two in a row.

What we discovered was that if you let off of the trigger very slowly, the hammer disengages and fires. As long as you let of reasonably fast everything is OK. We were able to recreate this every single time we let off slowly.

The really odd part about this was my son just had the exact same thing happen on his latest AR build. Mine was a PSA polished trigger kit and his was an Anderson Arms polished kit.

Could this have something to do with the way these companies are polishing their triggers?

 

[EvilKidsMeal]

My understanding was that polishing triggers increases the likelihood of double fires since it can loosen the specs a bit. This is why I haven't polished triggers. They polish naturally with use so I can only see that problem getting worse.

 

[Vigilant]

Polish should have something to do with it, as could improper assembly, or out of spec parts? Hard to diagnose over the net, but "polished" would be where I start?

 

[EvilKidsMeal]

Polish should have something to do with it, as could improper assembly, or out of spec parts? Hard to diagnose over the net, but "polished" would be where I start?

Yea I'd swap in a mil-spec fire control group, if you have one, and see what happens.

 

[CZB1962]

Yea I'd swap in a mil-spec fire control group, if you have one, and see what happens.

I plan to send PSA an email tonight and see what they have to say. Anderson sent my son a new FCG and it was OK. I just thought is was odd that we both had the same issue within a month of each other and two different companies.

 

[Vigilant]

I plan to send PSA an email tonight and see what they have to say. Anderson sent my son a new FCG and it was OK. I just thought is was odd that we both had the same issue within a month of each other and two different companies.

Not necessaril two different companies. Many companies source their parts from the same place, and brand them with their own name. I can call Monday, and with the right amount of cash, xpcan have uppers, lowers, LPK's, magazines, etc. made with my name on them. Difference comes with the specs you provide to the actual manufacturer! I can get cheap, mil-spec, mil-spec+, etc. depends on cash, and desired price point to the end user!

 

[17 squirrel]

Do you run your builds through a test procedure before you shoot it ??
There are some simple tests to go through that will tell you if your build is safe / user friendly when you are still at the workbench.
Google is your friend..

Also, check and recheck all the spring positions in the lower, if one is on the opposite side of where it belongs, you can get a double or worse.

 

[Tydeeh22]

The hammer is polished a bit too much. The hook that keeps ot from being full auto isnt big enough to grab reliably. Change out hammers.. keep shooting.

 

[RobbyMaQ]

My first AR did this after about 500 rounds. The builder mentioned having done some polishing/trigger work. At the time I dind't know any better, by my understanding now, is that this causes more wear as the hardened coating is now stripped. I replaced the trigger group with a new one from an LPK and it's fixed.

 

[1911ly]

The disconnector should have prevented a double fire even with a polished trigger. Somethng is wrong with that FCG. Definitely send it back.

 

[CZB1962]

Do you run your builds through a test procedure before you shoot it ??
There are some simple tests to go through that will tell you if your build is safe / user friendly when you are still at the workbench.
Google is your friend..

Also, check and recheck all the spring positions in the lower, if one is on the opposite side of where it belongs, you can get a double or worse.

I did check operation. I even checked to make sure the hammer stayed back on trigger release. What I did not do was release the trigger slowly which is when it happens. I will be adding this check to any future builds.

I am sure the springs are correct. I have assembled several ARs in the past.

 

[M67]

The disconnector should have prevented a double fire even with a polished trigger. Somethng is wrong with that FCG. Definitely send it back.

Yup

 

[sloughfoot]

It's called a bumpfire. It will happen anytime the shooter doesn't pull the trigger all the way back through recoil. It cost me 10 points once in a Garand match because I was milking the trigger.

Teach your son proper trigger control and the problem goes away. I kicked myself hard enough to make a bruise.

Or your disconnector is messed up. But if it was, the rifle would be full auto. It is a bumpfire.

 

[CZB1962]

It's called a bumpfire. It will happen anytime the shooter doesn't pull the trigger all the way back through recoil. It cost me 10 points once in a Garand match because I was milking the trigger.

Teach your son proper trigger control and the problem goes away. I kicked myself hard enough to make a bruise.

Or your disconnector is messed up. But if it was, the rifle would be full auto. It is a bumpfire.

Is is most definitely NOT a bumpfire. I can recreate it at will by holding the trigger as long as I want after a shot and letting it reset very slowly. If you let the trigger reset quickly there is no issue.

 

[sloughfoot]

OK. I believe you. Your disconnector is messed up. There can be no other answer. Polish of the sear surfaces can have no effect.

 

[sloughfoot]

Unless the sear engagement has been altered drastically. If so you should be able to recreate the hammer falling on trigger release with the upper and lower separated. You should be able to see it.

Sorry for the discombobulated responses. It's how I approach things sometimes.

Mount your trigger group on the outside of the lower and watch it real close. If it is not a bump fire, you should have no trouble recreating it. Good luck.

 

[17 squirrel]

Unless the sear engagement has been altered drastically. If so you should be able to recreate the hammer falling on trigger release with the upper and lower separated. You should be able to see it.

Sorry for the discombobulated responses. It's how I approach things sometimes.

Mount your trigger group on the outside of the lower and watch it real close. If it is not a bump fire, you should have no trouble recreating it. Good luck.

yep.. test and verify..

 

[midget]

Almost guarantee it is the hammer's sear face geometry.

 

[CZB1962]

Got home tonight and no response to the email I sent Saturday. I know they are not the best at shipping fast but I'm a little irked that they did not respond to my email.