View Full Version : What would cause this malfunction (doubling)?
RAM Engineer
07-03-09, 17:35
Ok, here's the situation.
The setup: New Daniel Defense M4 carbine. 16" Carbine length gas system. Complete factory rifle. Took it to the range to zero the iron sights and get a feel for it. Ammo was a mix of Q3131 and Remington 55gr FMJ. Magazines were a mix of Lancers, PMags, and TangoDown ARCs. I've contacted Daniel Defense and have not heard back yet. It's a holiday weekend, so I don't expect a reply for a few days.
The malfunction: Shooting from a bench, using the magazine as a monopod, I would get occasional (1-2 per magazine) doubling. One trigger pull, two shots fired. This occurred with all three types of magazines, and both types of ammo. No consistency as to WHERE in the magazine the malfunction occurred.
Took the lower off and did some experimenting. Below is what I found.
1. cock hammer manually
2. pull trigger and hold to rear
3. recock hammer manually (trigger still to rear)
4. place thumb on hammer and press downward and release
5. hammer falls on it's own accord almost 100% of the time.
Did the same with a friend's Noveske and hammer never moved in step 4 and 5.
I understand how all the parts in the upper work together, but lowers are a bit of a black box to me. I don't plan on fixing it on my own, since it is a new factory built gun, but for my own education, I'm curious as to what the cause (or causes) could be.
Any help would be appreciated. As soon as I hear from the manuf., I'll be sure to post an update in this thread.
Thanks,
Jason
do you have a lighter trigger....sounds like bump firing to me & why use the mag as a rest??
RAM Engineer
07-03-09, 20:25
do you have a lighter trigger....sounds like bump firing to me & why use the mag as a rest??
Nope, standard trigger. Pull weight FEELS (subjectively) identical to mil-spec trigger. No bump firing. I used the mag as a rest because it is convenient. I HIGHLY doubt that has anything to do with the malfunction, but mentioned it for completeness sake.
Another forum member has already PM'd me and correctly guessed the manufacturer. This other member's rifle was quickly fixed by the mfg. I have a second, identical rifle that was going to be a spare. I guess I need to drag it out and test the trigger...
Disconnector spring installed upside down?
Disconnector spring can cause doubling. Check it's installation and tension.
Doubling (also known as firing on release) is typically a malfunction of the FCG and the weapon should not be fired until this is fixed. One round is fired upon pressing the trigger and another is fired upon release of the trigger. Check the disconnector spring to be sure that it is not missing or upside down (large end of spring goes down). Next would be the disconnector, hammer, trigger. A broken hammer/trigger pin can cause doubling as well, since the positioning of engagement surfaces is off.
RAM Engineer
07-04-09, 19:10
The disconnector spring is the little coil spring between the trigger and disconnector, correct? Can I tell whether or not it's installed right-side-up without disassembling the lower?
Razorhunter
07-04-09, 19:33
It's perfectly fine to mention the manufacturer bro.
You may be able to see it, if you look closely, but probably not. If it were me I would disassemble the lower and look at everything very closely.
The disconnector spring is the little coil spring between the trigger and disconnector, correct? Can I tell whether or not it's installed right-side-up without disassembling the lower?
RAM Engineer
07-05-09, 14:57
You may be able to see it, if you look closely, but probably not. If it were me I would disassemble the lower and look at everything very closely.
Thanks for the info everyone. I was unable to duplicate this on any of my other lowers.
Iraqgunz,
I WOULD dissassemble it, except for two things:
1. I'm still waiting to hear back from Daniel Defense.
2. I have no idea what I'd be looking for (other than the upside down disconnector spring) if I did take it apart.
Jason
Ram E,
Just make sure that everything is assembled properly. Trigger and hammer springs in the right position. No burrs, etc... BTW- who makes the lower and lower parts kit? I would simply take everything apart and look anyways. I am fairly certain the manufacturer is going to tell you send it back.
Thanks for the info everyone. I was unable to duplicate this on any of my other lowers.
Iraqgunz,
I WOULD dissassemble it, except for two things:
1. I'm still waiting to hear back from the mfg.
2. I have no idea what I'd be looking for (other than the upside down disconnector spring) if I did take it apart.
Jason
RAM Engineer
07-06-09, 10:28
Ram E,
Just make sure that everything is assembled properly. Trigger and hammer springs in the right position. No burrs, etc... BTW- who makes the lower and lower parts kit? I would simply take everything apart and look anyways. I am fairly certain the manufacturer is going to tell you send it back.
IG,
It's a Daniel Defense M4. Still waiting to hear back from them.
Jason
I have had this same problem with two rifles over the last thirty years and both times it was traced back to the hammer. These GI hammers had too little sear surface to catch the trigger when cycling. It almost has to be either the hammer or the disconnector.
Hope you get it sorted out. A rifle that doubles is an accident waiting to happen.
openbolt
I recently developed the same problem in a well used RRA.
Turned out to be a broken trigger pin, which also caused the disconnector to be be egged out a bit.
New trigger pin, hammer and disconnector fixed the problem.
In a new gun, I would replace the disconnector, disconnector spring, and hammer to see if this helps. The parts may be slightly out of spec, or just at the wide ends of the tolerances.
RAM Engineer
07-07-09, 22:03
John at DD got in touch with me yesterday and they'll be sending me a return shipping label. Great customer service!
If possible please tell us what the verdict is. I would be very interested to see of they can replicate the malfunction and I am curious to see what it is.
John at DD got in touch with me yesterday and they'll be sending me a return shipping label. Great customer service!
Also interested in the turnaround time.
If possible please tell us what the verdict is. I would be very interested to see of they can replicate the malfunction and I am curious to see what it is.
I had the same issue but noticed the problem before firing the gun. I like to check function thoroughly before I fire a new gun. They told me it was a bad disconnector and when I got it back it had a new disconnector, hammer, and hammer spring(spring feels stronger). I had it back in a little over a week, they said they where sorry it took so long and where working on a new system to take care of warranty work even faster.
RAM Engineer
07-08-09, 10:32
Will do, guys. I emailed John again last night to clarify whether or not I need to send the whole rifle or just the lower.
JB51,
Thanks for posting in this thread. Did you have to send back the whole rifle or just the lower?
Thanks for sharing that info. If it were me I would have dug into it deeper first and possibly replaced a few small items, though I would still have contacted them and made the issue known. Glad to hear that they handled so quick.
I had the same issue but noticed the problem before firing the gun. I like to check function thoroughly before I fire a new gun. They told me it was a bad disconnector and when I got it back it had a new disconnector, hammer, and hammer spring(spring feels stronger). I had it back in a little over a week, they said they where sorry it took so long and where working on a new system to take care of warranty work even faster.
Ram Engineer, I sent the whole rifle to them as they requested so they could test the function of the rifle. Which they did, as soon as I opened the box I could smell the burnt powder.
Iraqgunz, I was going to fix it myself but I figured that I bought a complete rifle it should work right out of the box so they should fix it. Plus I havn't seen any parts locally so I would have had to wait for the parts anyway.
I hear ya. For me it's like a mechanic taking his car to Pep Boys to change the oil. ;)
Ram Engineer, I sent the whole rifle to them as they requested so they could test the function of the rifle. Which they did, as soon as I opened the box I could smell the burnt powder.
Iraqgunz, I was going to fix it myself but I figured that I bought a complete rifle it should work right out of the box so they should fix it. Plus I havn't seen any parts locally so I would have had to wait for the parts anyway.
I hear ya. For me it's like a mechanic taking his car to Pep Boys to change the oil. ;)
Lol, I am a mechanic and I have taken my car to Pep Boys to get the oil change. But in my defense I am a motorcycle mechanic and hate working on cars. Plus I don't think Daniel Defense in the gun world is the same as Pep Boys in the car world. I heard great things about their customer service, if it was from any other manufacturer I would have fixed it myself.
I was referring to my personal position only. I wasn't trying to compare the two. If I have to send my AR out for something like that I wouldn't be much of an armorer. ;)
Lol, I am a mechanic and I have taken my car to Pep Boys to get the oil change. But in my defense I am a motorcycle mechanic and hate working on cars. Plus I don't think Daniel Defense in the gun world is the same as Pep Boys in the car world. I heard great things about their customer service, if it was from any other manufacturer I would have fixed it myself.
I was referring to my personal position only. I wasn't trying to compare the two. If I have to send my AR out for something like that I wouldn't be much of an armorer. ;)
Yeah, I know what you mean. I am sure it was a 10 minute fix. I forgot to mention that the hammers where different too. The original was unnotched, the new one was notched and looks to be made of hardened steel.
RAM Engineer
07-08-09, 12:14
The hammers in my two DDM4 rifles are different, but I haven't had them side by side in the same location to compare yet.
RAM Engineer
07-21-09, 20:07
If possible please tell us what the verdict is. I would be very interested to see of they can replicate the malfunction and I am curious to see what it is.
It was delivered to DD's facility on the 16th. I sent an email to John today to ask if they were able to replicate, isolate and fix the malfunction. I'll post again when I hear back.
Alaskapopo
07-22-09, 03:46
do you have a lighter trigger....sounds like bump firing to me & why use the mag as a rest??
Magazines make great mono pods and do not induce malfunctions. Its a very stable way to shoot from prone or off a barrier.
Pat
Magazines make great mono pods and do not induce malfunctions. Its a very stable way to shoot from prone or off a barrier.
Pat
no arguements pat...op was at the bench.
I'll use the bald eagle front and rear rests & you can use the mono mag/pod if you want to bet for group size. ;)
Alaskapopo
07-22-09, 13:08
no arguements pat...op was at the bench.
I'll use the bald eagle front and rear rests & you can use the mono mag/pod if you want to bet for group size. ;)
Sorry did not read the post well enough. Your right off a bench bags are much better. I was thinking field work.
Pat
RAM Engineer
07-23-09, 20:09
Got the lower back today, exactly one week after DD got it. Invoice said they replaced the disconnector and the manual safety. Took the lower out of the box and tried the "manual hammer bounce" test and I could get the hammer to drop every time. I guess I'll take it out and shoot it just to make sure, but I'm 99% sure that it will still double.
I'll be contacting John at DD again soon, I think...
RAM Engineer
07-29-09, 14:00
So...
Gun is still doubling intermittently after getting it back. I spoke with John @ DD and told him I would try changing out the hammer and/or trigger with a Colt unit to see what would happen. THIS is what happened:
1. Changed out DD hammer for Colt Hammer. Problem persisted.
2. Went to change out DD trigger for Colt trigger. I noticed that I
couldn't get the DD selector switch to fit the receiver with the colt
trigger installed. The rear arm of the trigger blocked the bottom edge
of the selector switch hole. Just enough to block the selector from
fitting.
Do you think it is possible that the selector hole is drilled slightly
too low? This could prevent the trigger from it's full range of motion
rearward, possibly preventing proper engagement at full cock.
I found someone mention this in another thread:
"I received contact from DD customer service. They advised that after
inspecting my lower receiver it appears that the the hole for the safety
selector switch was drilled just a bit lower than called for by
tolerances."
In this thread: https://www.m4carbine.net/showthread.php?t=32579&page=2
to test that theory, you could take all the FCG parts and toss them in your Colt lower and see if it does the same thing.
You could also compare the distance of trigger pull from one receiver to another using a slide rule.
I would use the same set of parts per receiver to eliminate differences between the DD and Colt trigger groups
Sorry to resurrect an old thread, but I'm having the same problem with mine doubling on reset twice today for the first time. It's an Anvil Arms lower and parts kit I got ~4 years ago, though with <500 rounds since it wasn't with me for a while. What's a LPK or replacement hammer/disconnector set you guys recommend and where to get it?
Make sure it is assembled correctly. If it is then simply replace the disconnector spring with a good one. Colt comes to mind. See if that solves the problem.
Sorry to resurrect an old thread, but I'm having the same problem with mine doubling on reset twice today for the first time. It's an Anvil Arms lower and parts kit I got ~4 years ago, though with <500 rounds since it wasn't with me for a while. What's a LPK or replacement hammer/disconnector set you guys recommend and where to get it?
Aha! I checked the disconnector out and according to another source the disconnector spring was upside down--big side up instead of little side up. I put it back together with the skinny side up (holy **** what a chore) and going to the range to see how it does. I guess that's one upside of building my own as it made me familiar enough with it down to the smallest parts.
The easy way to install it is to use a punch and push it into the hole.
Aha! I checked the disconnector out and according to another source the disconnector spring was upside down--big side up instead of little side up. I put it back together with the skinny side up (holy **** what a chore) and going to the range to see how it does. I guess that's one upside of building my own as it made me familiar enough with it down to the smallest parts.
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