AR double tap problem

[True.grit]

Howdy,

I have a AR that I built that has been giving a double tap intermittently. It is fresh built that has less than 200 rds through it. The upper is a Yankee hill 9mm with a conversion block. The lower is billeted and I used a single stag trigger. If any one has any info on how to fix or where to start it I would be grateful. I have built a few ARs but this is my first attempt at a sub gun. Thanks

[Larry Gibson]

Did you do a "trigger job" on it? That is the usual problem.

Larry Gibson

[tomme boy]

Try a new hammer and disco. If not, is the disco spring upside down?

[roysha]

Single stage trigger? Does this mean an after market single stage trigger (adjustable or non-adjustable) or is it the "stock" trigger that came with the kit.

First thought is what the above post suggested.

If it is factory, and a "trigger job" was not done, are you sure the disconnector is moving freely in it's slot. I had one that due to a burr on the side of the slot, retarded the movement just enough to cause an occasional hammer follow. Also I have seen damaged disconnector springs that would not allow the disconnector to set quickly enough to catch the hammer. You should have a rather difficult time pushing the disconnector down with your finger because of the spring tension. If it moves fairly easily, replace the spring.

I had your problem with a Jard adjustable and it was caused by having the disconnector set too close. Tweaked the screw about 3/4 turn and all is well.

[True.grit]

There are 2 springs in the trigger, which one is the disco spring??

I have not done a trigger job. What would need to be done? The trigger has about a 4lb pull. It shoots great with cast reloads.

[True.grit]

roysha, The single stage trigger was a lower kit from CMG. It was priced right so maybe it is the problem. Sounds like the Jard adjustable is the way to go if I have to spend any more money. I will check the disconnector it could be a burr. I have some anti-walk pins from dpms I wonder if that could be part of the problem as well.


Thanks everyone for the info.

[nhrifle]

The disconnector spring is a small coil spring the is easily confused with the bolt catch spring. Look at the springs carefully, the disco spring has wider coils at the bottom so it snaps into the trigger recess and stays in place. If that is put in upside down it can cause the disco to malfunction and cause a sticky situation with the ATF.

[MtGun44]

Do not fire the gun where others are present until this is fixed. ATF has successfully
prosecuted people for a malfunctioning AR - calling it an illegal full auto, and prison time
was given. This is not a joke.

Bill

[zomby woof]

Look out for high primers too.

[badge176]

I had similar problem with my .40S&W upper (Olympic) when I left the Heavy (H2) buffer in the gun.the pistol cal uppers are blowback operated and the rounds weren't pushing the combined weight of the bolt, carrier and the buffer weight back far enough to catch the disconnector. Switched to the standard buffer weight and all was right. Can also be the effect of too light a load for the buffer weight and receiver extension/ recoil spring.

[badge176]

I'd check the BC load(s) firing one round at a time, and be sure to hold back the trigger to confirm disconnector reset. Shoot like this for a couple dozen round to be certain that the load has enough Hrumpf to get the bolt carrier back hard enough to shove the hammer into the disconnector. Had similar 'doubling' problem with a Marlin Camp 9 that had the Wolff extra power recoil spring in (I had run through a heap of surplus Sub-gun European 9mm (+p hot!)) but then switched to US commercial loads and got doubles for same reason...

[tomme boy]

The only way they would prosecute this is if you were doing something else like drug dealing or stolen guns. It is a malfunctioning firearm you are trying to fix. Thats it. When you hear about people that are prosecuted, you are not hearing the rest of the story.

[Postalpaul]

I think Tomme Boy has got it "is the disco spring in upside down"
You quoted "it has a 4lb trigger pull" sounds kinda light unless it was built to be light

[MtGun44]

Sorry, you are wrong about ATF. The guy loaned the gun to another shooter, and it "briefly went full auto
and jammed".

ATF was informed and confiscated the gun. No amount of explanation by his lawyer to the
ATF employee "judge" would dissuade them from a prison sentence. It has been appealed and lost.
The fact that the gun was malfunctioning due to worn/broken parts and/or out of spec ammo
was totally irrelevant - they wanted a conviction. ATF repeatedly stated that if the gun fired more
than one round per trigger pull - regardless of why - it is a machine gun and by loaning the rifle
he had "transferred a machine gun". They made a big deal of the fact that it had malfunctioned
on a previous occasion.

http://totalrecoil.wordpress.com/2008/08/08/malfunctioning-ar15-becomes-a-machine-gun/

Bill

[True.grit]

OK

Tomme Boy was right disco spring in upside down. All good now. Whew!!!

Thanks guys for all the info.

[tomme boy]

The man you are talking about knew it was bad and would not fix it. He knew is was bad and lent it to another. This showed disregard to safety for everyone around him and the person he lent it to. I'm telling you, you don't know the whole story. The BATF are not the "Bogeyman" everyone believes they are.

[koehlerrk]

The man you are talking about knew it was bad and would not fix it. He knew is was bad and lent it to another. This showed disregard to safety for everyone around him and the person he lent it to. I'm telling you, you don't know the whole story. The BATF are not the "Bogeyman" everyone believes they are.

By and large, no, they're human beings, just trying to do their jobs. But some of them let the authority go to their heads, and woe unto those who make a minor mistake in their presence.

That is not a problem unique to the BATFE either, any and all flavors of law enforcement suffer the same issue, the problem being human beings. I've met good cops, and bad cops, good game wardens, and bad ones too. Power corrupts, and some people are more susceptible to corruption than others. My own rule of thumb, the more a man desires a position of power and authority, the more likely he is to be corrupted by that power and authority.

[Johnny_V]

Are you using home brewed loads. If so, try changing to the CCI M41 5.56mm NATO-SPEC primer. This primer is made specifically for those that handload cartridges used in SA or FA military style weapons. Military-style semi-auto rifles seldom have firing pin retraction springs so the sensitivity specs of these primers is designed to prevent "slam-fires", or as you call it, "double tap". You can check these out at Graf & Sons (http://www.grafs.com/retail/catalog/product/productId/2448).

Hope this helps......

[country gent]

My wifes match rifle was built from mostly armlite parts. She had been competig almost 2 years in NRA High Power when the 2 stage trigget started messing up. Never figured it out But it started firing on the pull and then on the release of the trigger. Re[placed it with a jewel and set it to 4 1/2+ lbs to meet NRA rules. Rifle never missed a beat then.

[MtGun44]

According to a friend, his business partner was an ATF agent for about a year. When I asked my
non-shooter friend who is totally ignorant of any gun right stuff or any other info on ATF said "Because
he couldn't stand to work with a bunch of crazy out of control cowboys."

I about fell over, knowing he had ZERO other info about ATF, and did ask him if he was kidding or
playing a joke. He was quite serious that his partner had resigned in disgust over non-professional
behavior as the norm. According to a friend that works at the FBI, when the head of the FBI was
asked to take the ATF in as a division his comment was - "You know what you get when you mix
dirty water with clean water?"

Believe what you want about ATF, and I am sure that there are many good folks there, but all I have
found is that they are rabidly anti-gun and will do everything they can to screw you over. I am
extremely careful to stay on the right side of the gun laws, knowing that there is never any
"benefit of the doubt" given.

Bill

[destrux]

OK

Tomme Boy was right disco spring in upside down. All good now. Whew!!!

Thanks guys for all the info.

Glad to hear you found the problem. For future reference, the hammer spring being in backwards can also cause this problem.

[Postalpaul]

Thread ninjas were I'm full force here

Glad you got it fixed!

[Dutchman]

http://en.wikipedia.org/wiki/United_States_v._Olofson

http://www.elfie.org/~croaker/batfabus.html

[Kanitz8541]

I have had the same problem on a few ARs I've built. Question: when you charge the firearm has it ever discharged. I am willing to bet that your firing pin is a few thousands to long. After a long night reloading I loaded a magazine in 5.56 and when I inserted it and charged it. The rifle went off and I had to force a malfunction by dropping the magazine. Needless to say I had a cop show up and he had the same problem. So we talked hand jamming and casting for n hour them he left. I checked my primers, measured everything and the rounds checked out. Tried a few more times to charge the rifle and again it happened. So I thought a little while and figured it out. Turns out the firing pin was a few thousands to long. So I walked to my drive way rubbed the firing pin on the concrete a few times and it hasn't happened again. I hope this helps.