AR doubling

[Uncle Alvah]

Hello!
I have a friend with an AR that is sometimes "doubling", that is, fireing two shots with one pull of the trigger. Happens maybe once in a 30 round mag, although he's not shot it much(purchased used, Del Ton upper on a Bushy lower), 'cuz of this problem.
I suggested he check the fireing pin is free, and if so, then replace the hammer and disconnector.
I'm hardly an expert on the AR platform however, so I thought I'd seek the additional advice of others here.
THANKS!

[A-Bear680]

This should help:
www.m4carbine.net/showthread.php?t=33700&highlight=doubling

[jaxman7]

Do you know if he or anyone else has messed with the lower? Has there been any dis/reassembly of the lower? Any modifications to it such as new trigger unit, new springs,etc.?

[Iraqgunz]

Assuming that it was assembled correctly with the right parts, I would say start with the disconnector spring. If that doesn't work then a new disconnector. I would absolutely not fire it anymore until the problem is fixed.

[bvmbandit]

I have purchased hammers with pin holes out-of-center. This little problem would be one to check as well.

My 2 cents...

Scott

[Shotdown]

Assuming that it was assembled correctly with the right parts, I would say start with the disconnector spring. If that doesn't work then a new disconnector. I would absolutely not fire it anymore until the problem is fixed.

I've had a friend with this same problem.

[bkb0000]

how many rounds on the weapon, and when did it start doubling? i assume a standard trigger assembly with no modifications? does it fire two fast rounds before reset, or does the second round fire at reset (on release of the trigger)? if he's not sure about this, tell him to hold the trigger in after each shot. if the weapon fires at reset, it's gonna be a problem between the hammer/trigger sear interface. if it fires two rounds with the trigger squeezed and held, it's probably the disconnect.

[A-Bear680]

Don't fire it at a public range...

Why fire it at all? What is special about a public range?

[NCPatrolAR]

If you want to talk about someone's continued, purposeful flaunting of the law netting them a felony conviction; take it somewhere else.

[CarlosDJackal]

A guy at my club started experiencing this when he incorrectly assembled an AR without the disconnector spring. That would be one of the things I would check.

Good luck!!

[A-Bear680]

Looks like the clutter in the thread got pruned pretty hard on Saturday night -- OK , maybe early Sunday morning. A few posts disappeared.

[Uncle Alvah]

Well, the disconnector spring was installed correctly, it was suggested it might be upside down.
He went ahead and changed the spring, and the disconnector also, although he said all the sear surfaces appeared OK. Has not test fired it since changing the parts.

[Iraqgunz]

I would also make sure that there are no full auto parts in the LPK. Especially a select fire selector lever.


Well, the disconnector spring was installed correctly, it was suggested it might be upside down.
He went ahead and changed the spring, and the disconnector also, although he said all the sear surfaces appeared OK. Has not test fired it since changing the parts.

[RAM Engineer]

Besides all the good advice already given, I had a Daniel Defense that would double about once or twice a magazine. Two trips to DD and changing out the internals for known good Colt parts did not resolve the problem. It was finally determined to be a lower with the selector switch hole drilled ever so slightly too low. DD finally changed out the lower for a new one and the problem was solved.

[Uncle Alvah]

Especially a select fire selector lever.

How can he differentiate between the two?

[Iraqgunz]

A select fire one will have grovves in it, the semi auto ones are flat and won't allow the tail of the disconnector to dip down in the back. I am sure that you can get a close up onlines (Google-Fu).


How can he differentiate between the two?

[Uncle Alvah]

Like this, I assume?

http://i18.photobucket.com/albums/b134/UncleAlvah1/sel.jpg

[JonnyVain]

Check your PMs for your infraction notice.

[bkb0000]

if your comments were regarding the individual who was prosecuted for electing not to repair a weapon which was firing more than one round per trigger pull, that topic has been debated to death, and is verboten in these parts.

[A-Bear680]

Well, the disconnector spring was installed correctly, it was suggested it might be upside down.
He went ahead and changed the spring, and the disconnector also, although he said all the sear surfaces appeared OK. Has not test fired it since changing the parts.
Might not hurt to bench test the gun for disconnector function , and so on. There are a few different ways to do that.