View Full Version : ar-15 double firing

November 17, 2010, 09:41 AM
I recently built a Delton AR-15. I've put around 500 rounds through it with almost no problems - but every now and then, it fires 2 rounds in quick succession. It's not dangerous since the rifle is still pointing downrange but it's pretty worrying all the same. I don't like rounds going off unexpectedly! I thought at first that it might just need to be "broken in" but 500 rounds later it's still happening. It happened twice last time I used the rifle. Any ideas?

November 17, 2010, 09:44 AM
It could be a bump fire. I would disassemble the trigger group and inspect it for any wear.

November 17, 2010, 09:46 AM
I would disassemble the trigger group and inspect it for any wear.

OK. I know there was no wear when this first happened because everything was brand new and I assembled the trigger group myself. But I'll check it anyway.

November 17, 2010, 11:06 AM
Could be an out of spec trigger or hammer. I had this happen on an AR years back. The gun would fire a second round when I let off after the first shot.

November 17, 2010, 11:19 AM
Did it pass the function checks ok? (You DID do them, right?)

For the record, here's what you do with a new lower:
1) Install upper. Ensure the chamber is clear.
2) Ensure the hammer is cocked. Turn off safety. Pull trigger. It should fall.
3) Re-cock the hammer using the charging handle. It should stay cocked.
4) Turn safety on. Pull trigger. Hammer should NOT fall.
5) Turn safety off. Pull trigger. Hammer should fall.
6) While holding trigger down, re-cock with the charging handle and let it slam forward on its own (don't ride it down). Hammer should NOT fall. If it does, you have a problem with the hammer/disconnector engagement.

My guess is that you're either bump firing (not likely) or the disconnector and hammer aren't playing nice. What parts kit did you use (guessing Del-Ton)?

Bartholomew Roberts
November 17, 2010, 11:24 AM
You need to function check that rifle.

1. Unload the rifle and remove the upper from the lower.
2. Using only the lower, cock the hammer.
3. Pull the trigger to the rear and hold it there (use your offhand to catch the hammer as it releases and keep it from slamming into the bolt catch)
4. Still holding the trigger to the rear, cock the hammer again.*
5. Release the trigger**

*If the hammer does not catch the disconnector, you have a problem with the hammer or disconnector - one or both may need to be replaced.

**If the hammer goes forward at this stage, you have a problem with the nose of the trigger or the notch in the hammer - one or both may need to be replaced.

You may want to repeat that function check several times if the problem is only occasional. What you are describing is a classic trigger group problem and usually what causes it is some enterprising person decided to do a home trigger job on the rifle by polishing the nose of the trigger. The case hardening is very thin here and if you polish through it, it can wear very fast. You can also run into problems when you get parts that weren't properly case hardened to begin with.

If you can't repeat the problem with the above described function check, then you may be inadvertently bump-firing the rifle.

If you have a problem in the fire control group, I would advise Delton and have them send you new parts (assuming you haven't been doing any home trigger jobs).

November 17, 2010, 12:04 PM
Thanks guys. Yes, I have done all those tests both with the upper attached and with it removed. I didn't find any malfunctions, but of course, as mentioned, it is an intermittent problem.

I absolutely did not attempt to polish or otherwise tamper with any of the trigger components. I have always noticed that the trigger pull is absolutely terrible, it's like the trigger on a toy gun, but I assumed that is because it was as cheap as hell.

It is a Delton kit, all the parts for completing my stripped lower, plus a pre-assembled and test fired upper came from them as a kit.

I presume "bump" firing means I am pulling the trigger in rapid succession? I am almost 100% certain that I'm not doing that, but I will pay more attention next time.

Bartholomew Roberts
November 17, 2010, 12:24 PM
I presume "bump" firing means I am pulling the trigger in rapid succession?

Bump firing (http://en.wikipedia.org/wiki/Bump_fire) happens when the recoil of the rifle and some forward pressure causes the trigger to bump against your trigger finger during recoil, causing it to fire again. People do it for fun sometimes; but it can also happen accidentally if the conditions are right.

From what you are describing, I am guessing wear on the trigger nose due to improper case hardening or out of spec trigger. If so, it should show up during a function check; though if it is only showing up every twice every 100 rounds or so, the wear may not have hit the point where it will be easy to spot yet.

November 17, 2010, 12:52 PM
Unfortunately this is one of those subjects that's extremely serious.

Your rifle is, according to the BATF, an illegal machinegun. If you are seen by law enforcement firing this rifle, you can be arrested and the ATF will charge you with a felony.


Do not attempt to fix this problem yourself. Do not post video of the gun malfunctioning on YouTube. Don't talk about it on the internet. Just box the gun up and immediately send it back to the manufacturer for repairs.

November 17, 2010, 01:50 PM
Absolute nonsense. Get it fixed. I happens periodically with out of spec parts. NOT ONE SINGLE CASE exists of a guy getting into trouble for a malfunctioning weapon.

Now if you're like that idiot in Wisconsin who put an A2 burst kit in his junky Oly Arms.... you could get a little time in the pokey.

November 17, 2010, 02:09 PM
What ammo is this happening with? The ARs are noted for slam fires because of the floating firing pin. If you're using something like Federal ammo, their primers are soft and slam fires will happen occasionally. If you hand load, use the CCI 41 primers or expect issues.

November 17, 2010, 02:11 PM
The same thing happened to a rental AR a while back. It would fire a shot when the triger was pulled, and when the trigger was released. The RO told me it was "loose pins". See if yours is doing the same, and get it fixed.

November 17, 2010, 02:16 PM
I don't hand load. I've used 3 brands of ammo in total - actually I'm not sure which type I was using when it happened. The 3 types I've used were Black Hills, Ultramax (re-manufactured) and Silver Bear - mostly silver bear, I've fired at least 400 of those.

NOT ONE SINGLE CASE exists of a guy getting into trouble for a malfunctioning weapon.

What about the case that Sturmgewehre linked to?

November 17, 2010, 02:22 PM
Out of spec parts,likely.Saw this on an AR-10 from the factory.A very gradual trigger pull finds a place.There are 2 sets of hooks,one is the disconnect.A little out of spec and a slow trigger pull,the disconnect hooks don't catch.
You might try a Rock River 2 stage match trigger.

November 17, 2010, 02:44 PM
There was a guy at the range a few years back, with a Bushmaster Varminter. The gun fired just fine with him behind the trigger, but when he let me fire a few rounds off, my trigger pull resulted in a double-fire. I followthrough, meaning, I squeeze the trigger and continue to keep the trigger squeezed after the round fires. I only release the trigger after I am ready for my next shot. That kind of follow through somehow made it fire twice.

The other guy was not doing any follow through. He would release the trigger immediately.

Bartholomew Roberts
November 17, 2010, 02:51 PM
I don't think the problem is slamfiring since that would typically be several rounds fired at once, not just two.

What about the case that Sturmgewehre linked to?

Suffice it to say that Mr. Olofson (http://thefiringline.com/forums/showthread.php?t=275955) had a few more problems than just a malfunctioning rifle (http://thefiringline.com/forums/showthread.php?t=335832&highlight=olofson).

However 18 U.S.C. 921(a)(23) and 26 USC 5845(b) define a machinegun as "any weapon which shoots, is designed to shoot, or can be readily restored to shoot, automatically more than one shot, without manual reloading, by a single function of the trigger."

Assuming your rifle is doubling and it is not a bump-fire problem, whether or not your rifle is now an unregistered machinegun under these laws turns on whether or not the rifle firing again when the trigger is released is "a single function of the trigger." To the best of my knowledge there is no case law on the subject, which suggests that ATF is normally understanding of this issue since it isn't an uncommon one with ARs.

However, since you know you have a problem and you are in a very grey area of law where the penalty is a federal felony with a minimum 5 year sentence, I would get it fixed as soon as possible if I were you.

November 17, 2010, 03:58 PM
Probably the easiest thing is to get a new trigger group and install it- I'd probably buck up for a Rock River or Daniel Defense LPK, and then the rest of the parts are just spares you can keep.

If the problem goes away, then contact Del-Ton for a replacement of those parts, and then keep THOSE as spares. Or just give in to Black Rifle Disease and build another rifle. :D

As for the case mentioned, only in the most simplistic and complimentary to the defense view was it "malfunctioning." The guy used full auto parts, knew it would run full auto, and never once took the rifle out of service or presented it to anyone for repair. This has been hashed out multiple times on multiple fora. So long as you recognize you have a problem and seek to fix it you will be fine. If you shrug, laugh that you have a "full auto" rifle, and loan it around to friends with no intention of ever repairing it, then you might run into trouble.

S. Fisher
November 17, 2010, 08:05 PM
Replace your dis-connector spring, it sounds like you have a weak one.

November 17, 2010, 08:15 PM
I've seen this with Del-ton parts kit once before with my friend.
He returned the trigger parts to Del-ton and they sent him a new set but the problem was not completely solved. He replaced the trigger parts with one from RR and the problem went away. I think quality of Del-ton parts are pretty poor.