I want to start by saying, please forgive me if this is a noob question, and I should already know the answer.

I have a DPMS Oracle A-15 .223/5.56, after putting about 1000 rounds through it throughout the day I was noticing the ejector fail a little. After getting it home and cleaning it, I reassembled the weapon, and wanted to test the ejector. So I proceeded with the following:

1. Opened, and locked the bolt in the open position
2. Securely inserted one live round into the chamber
3. Pressed the bolt release button (confirmed my finger was no where near the trigger)
4. BANG, gun went off.

Being the responsible gun owner I am, the round discharged itself in the ground, and no one was harmed. But I am trying to understand what went wrong? I have done this same pre loading the barrel by hand on many other makes and models of guns, and have never once had an issue. Many owners manuals actually suggest using this method for firing the gun without a magazine. I want to repeat, my finger was no where near the trigger, and the gun functioned just fine after this without ever taking it apart again before shooting.

Is this expected behavior for this gun? Either way, how did this happen? Is this not something you should do with this gun? Are there other types of guns I should be aware of that I should not do this with?

Thank you all in advance for your help!

First, get a damn snap cap. Glad no one got hurt.

Are you SURE that you didn't pull the trigger? Be honest. If you even think you're not sure, you probably did pull the trigger.

AR-15 type rifles have a floating firing pin, so it is possible that that upon closing, the firing pin had enough energy to set off the primer. This is pretty rare though. There could be several contributing factors that could have caused this. A poor;y seated primer, a soft primer, an out of spec firing pin, to name a few.

Next time, buy some dummy rounds or use expended brass to test stuff like this.

Soft primer + not using a magazine would be my guess. What kind of ammo? Reloads?

And yes, I would always use a mag.

Soft primer combined with the free floating firing pin and a bolt closing at full speed with no magazine to slow it down.

Which ammo?
Which trigger?
What was the problem you were experiencing with the ejector?

Take rifle to a smith and contact manufacturer.

What kind of ammo? There are a few companies that use standard type primers instead of the cci41 or wolf 5.56 that most of us use?

It can happen. Rare. Never had it happen but once and it was loading from a magazine with the gun benched and safed after the range went hot from a cease fire.
Never hurts to make sure that the fire control group function checks correctly because it can also happen from hammer follow if the hammer was not properly retained by the trigger or disconnector. Also make sure the bolt face is free of debris. Something stuck to the bolt face near the firing pin hole can cause it also.

Whoops, nm.

My guess is dirty firing pin may have been stuck forward, as opposed to being loose to move back and forth before the hammer strikes it

Can't happen. The firing pin does not even come into play untill the bolt is locking in. When the gun unlocks the firing pin is held by the rear of the carrier and the bolt is pulled forward away from the firing pin.

My guess would be this, also known as a slamfire

Didn't know that. Learn somethin new everyday. lol

I am 1 million percent sure I didn't pull the trigger. I was being extra alert since I was in the city, and remember physically looking at my finger to confirm I was below the trigger guard.

I will confirm I was not using a mag, but why would that matter? The ammo was just the cheepo federal brand from cabellas. Not reloads but new.

Ammo: Store bought Federal .223 rounds (not reloads)
Trigger: Trigger that came with the gun, never been removed
Ejector issue: I was out in some really dirty areas and got a bunch of crap in the ejector, just needed to be cleaned. Wasn't actually broken or anything.

if the round is already in the chamber and there is no mag, you arent going to have any friction/resistance from the bolt having to push the round out of the mag and into the chamber.  there is also probably some friction from the mag itself.  

i've only ever see an SKS slam fire like that.  glad no one got hurt.

I would guess FCG malfunction (hammer following the BCG). caused by a worn, dirty or modified FCG, OR a stuck firing pin (remove BCG from gun and tip it vertical then horizontal to see if the firing pin slides on it's own), OR excessive firing pin (defective firing pin) protrusion (check with firing pin protrusion gauge), or a soft, over-sensitive, or improperly seated primer.

Read dano's post.

Accidental Negligent Discharge on Bolt Close

Call it what it is.

i've always wondered why people get nitpicky over this, frankly, after 4 years in the military, what op describes i DO see it as a accidental discharge, since op NEVER pulled the trigger, hit the  trigger, or purposely tried to get the hammer to strike.

the easiest way i would say to describe this, did the user perform a action with the intent to cycle teh weapon, (if yes adn roudn is discharge neglegent fire) did the user perform a action that should NOT of cause a round firing(loading a round, extracting a round etc) then accidental.

Accidental discharge and a good lesson.

The difference is, I am not in the military. I do not have a DI chasing after me to make sure I didn't blink too many times in the last hour. And where procedure in the military might say you are neglectful if you don't spit shine your boots every day, I wouldn't say what i did qualifies as neglectful in any way.

Now if say, the manual that came with the weapon specified not to do this, and I just failed to listen, than yes, neglectful. But after owning many guns for a very long time, and many of the manuals actually suggesting this method, there was nothing telling me I shouldn't do what I did. No range master, no DI, no user manual, none of the other shooters that were with me (two of which were Marines, including an Armorer).

I'm not even necessarily saying that me not knowing qualifies the absence of neglect, but when people that have been trained to maintain these guns by our military don't know about this issue, I would hardly say it is common knowledge, let alone anything but accidental.

http://quarterbore.com/library/pdf_files/fm23_9v1.pdf


To put it as nicely as possible, I highly doubt your story about a USMC armorer being present for your event and having no clue as to what could have gone wrong.