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Posted: 9/9/2005 12:58:28 PM EDT
So I was at the range today and I went through about 5 or 6 30rnd mags pretty quick. Inserted a new mag, hit the bolt release and BANG! Rnd struck about 5 yds in front of me. Scared the shit out of me so the next rnd I rode the bolt as I closed it and used the forward assist. Nothing. Fired the rest of the mag and disassembled the upper. Nothing stuck in the carrier or on the bolt. Only thing I can guess is that there was enough momentum for the firing pin to hit the primer and the primer was unusually soft. Reassembled and it functioned fine for another 120rnds. All I can guess is it was the primer. Just goes to show how important muzzle discipline really is. Rifle is a Colt R6520 with a M16 bolt carrier. Ammo was WWB 55gr.
Link Posted: 9/9/2005 1:16:17 PM EDT
slam fire?
Link Posted: 9/9/2005 1:27:16 PM EDT

Originally Posted By eklikwhoa:
slam fire?



Sounds like it.
Link Posted: 9/9/2005 1:30:28 PM EDT
[Last Edit: 9/9/2005 1:32:10 PM EDT by mobius]
that is definetly a slam fire..........disassemble the bolt carrier assy and clean it, especially the bolt itself where the firing pin goes into, the firing pin isn't freely moving......some junk, carbon or gease is the cause........the other possibilty might be the firing pin might be bent.
Link Posted: 9/9/2005 1:36:02 PM EDT

Originally Posted By mobius:
that is definetly a slam fire..........disassemble the bolt carrier assy and clean it, especially the bolt itself where the firing pin goes into, the firing pin isn't freely moving......some junk, carbon or gease is the cause........the other possibilty might be the firing pin might be bent.



Third posibility (though very rare w/factory ammo), a projecting primer. Most often occurs w/handloads, but every once in awhile I have seen a factory round w/one.
Link Posted: 9/9/2005 5:31:42 PM EDT
Link Posted: 9/9/2005 5:44:42 PM EDT
This is why it is taught to ALWAYS keep weapon pointed down range. I wouldn't worry at all, unless it happens a lot. Probably the ammo's fault. It might scare you, but it's good for a laugh as long as your using proper safety precautions. It seems like you know what your doing, you didn't kill anyone.

If i woulda been there, I woulda LMAO!!!
Link Posted: 9/9/2005 5:51:08 PM EDT
You shouldn't be chambering a round unless the weapon is pointed down range!

At the regulated range I go to most often, weapons are pointed down range unless and until they are put in a case to be carried off the line.

I know you are only asking a tech question concerning why this may have happened with your rifle. But it's important and affects all of us since everything any target shooter or hunter does affects public opinion of shooting.

Be safe. Good shooting.
Link Posted: 9/9/2005 6:17:45 PM EDT

Originally Posted By Epeeman:
You shouldn't be chambering a round unless the weapon is pointed down range!

At the regulated range I go to most often, weapons are pointed down range unless and until they are put in a case to be carried off the line.

I know you are only asking a tech question concerning why this may have happened with your rifle. But it's important and affects all of us since everything any target shooter or hunter does affects public opinion of shooting.

Be safe. Good shooting.



Good advice.
Link Posted: 9/9/2005 6:22:33 PM EDT
[Last Edit: 9/9/2005 6:22:51 PM EDT by Boog]
guys, it sounds like the weapon WAS pointed downrange.

Make absolutely sure you take the bolt apart and the extractor off and clean and inspect the firing pin channel.
Link Posted: 9/9/2005 6:28:36 PM EDT
[Last Edit: 9/9/2005 6:28:59 PM EDT by BravoSierra]
anybody remember this one?


Their are two types of people: Those that have had AD's, and those who are about to.
Link Posted: 9/9/2005 10:57:53 PM EDT

Originally Posted By shamayim:

Originally Posted By mobius:
that is definetly a slam fire..........disassemble the bolt carrier assy and clean it, especially the bolt itself where the firing pin goes into, the firing pin isn't freely moving......some junk, carbon or gease is the cause........the other possibilty might be the firing pin might be bent.



Third posibility (though very rare w/factory ammo), a projecting primer. Most often occurs w/handloads, but every once in awhile I have seen a factory round w/one.



+1 on both posts!

Check out what they said and you'll be good to go. After checking everything out, UNDER SIMILAR SAFE CONDITIONS, try loading a round again via the bolt release. Just to be sure it does not happen again and that the rifle is working as it should.

Stay safe and glad nothing serious came out of it.
Link Posted: 9/9/2005 11:39:49 PM EDT
Probably NOT a high primer or a slam fire but a bounce fire. The shock of the action caused the sear to bounce, preventing engagement.

What ever it was, it wasn't an out of battery experience.
Link Posted: 9/10/2005 12:38:45 AM EDT

Originally Posted By cms81586:
So I was at the range today and I went through about 5 or 6 30rnd mags pretty quick. Inserted a new mag, hit the bolt release and BANG! Rnd struck about 5 yds in front of me. Scared the shit out of me so the next rnd I rode the bolt as I closed it and used the forward assist. Nothing. Fired the rest of the mag and disassembled the upper. Nothing stuck in the carrier or on the bolt. Only thing I can guess is that there was enough momentum for the firing pin to hit the primer and the primer was unusually soft. Reassembled and it functioned fine for another 120rnds. All I can guess is it was the primer. Just goes to show how important muzzle discipline really is. Rifle is a Colt R6520 with a M16 bolt carrier. Ammo was WWB 55gr.



possible cook-off after 6x30 rds?
Link Posted: 9/10/2005 12:50:51 AM EDT
[Last Edit: 9/10/2005 12:52:49 AM EDT by f2]
re: cookoff, that's what I was thinking. Another round should have chambered if so.

eta:

Fired the rest of the mag and disassembled the upper. Nothing stuck in the carrier or on the bolt.
Didn't you do this part backwards?
Link Posted: 9/10/2005 12:57:28 AM EDT
[Last Edit: 9/10/2005 12:57:41 AM EDT by steve-oh]
Had to have been the M16 carrier.

E­TA: its a joke
Link Posted: 9/10/2005 1:11:09 AM EDT

Originally Posted By tugboat:

Originally Posted By cms81586:
So I was at the range today and I went through about 5 or 6 30rnd mags pretty quick. Inserted a new mag, hit the bolt release and BANG! Rnd struck about 5 yds in front of me. Scared the shit out of me so the next rnd I rode the bolt as I closed it and used the forward assist. Nothing. Fired the rest of the mag and disassembled the upper. Nothing stuck in the carrier or on the bolt. Only thing I can guess is that there was enough momentum for the firing pin to hit the primer and the primer was unusually soft. Reassembled and it functioned fine for another 120rnds. All I can guess is it was the primer. Just goes to show how important muzzle discipline really is. Rifle is a Colt R6520 with a M16 bolt carrier. Ammo was WWB 55gr.



possible cook-off after 6x30 rds?



I doubt it was as cookoff. I have never heard of an instant cookoff when a round was chambered.
Link Posted: 9/10/2005 4:56:17 AM EDT
It should take a lot more than 150 rounds of semi-auto to make the rifle hot enough to cook off a round. A LOT MORE!

I don't think it was a cook off. Probably stuck firing pin or a sear bounce. Either way, CLEAN, CLEAN, CLEAN the rifle to keep it from sticking the pin, and clean the lower really well too, because gunk can interfere with the FCG's operation as well.
Link Posted: 9/10/2005 1:11:30 PM EDT
I believe it's more a matter of rate of fire vice number of rounds to reach cook off temperature. It took less than four magazines to cook off some blanks during training (of course, this was auto fire).
Link Posted: 9/10/2005 1:32:29 PM EDT
Had the round that was chambered been repeatedly cycled previously?if so every time a round gets chambered the firing pin makes a tiny dent.Over the course of repeated chamberings it can eventually go off when chambered.
Link Posted: 9/10/2005 3:51:13 PM EDT

Originally Posted By steve-oh:
Had to have been the M16 carrier.





If he had a non-modified M-16 firing pin in there it 'may' have contributed to the accidental firing. An M-16 firing pin has a little more mass to it and does tend to smack the primer with a little more force then an AR-15 firing pin. A non-modified M-16 bolt carrier is also more prone to slam fires...
There is a reason that Colt and others have cut and modified the AR-15 bolt carriers near the firing pin. (To help prevent slam fires)
Link Posted: 9/10/2005 4:01:12 PM EDT
I had a sear engagement problem that caused this very same situation. I had to replace the trigger and the hammer to fix it.

Bob
Link Posted: 9/10/2005 5:55:40 PM EDT
Link Posted: 9/10/2005 6:02:53 PM EDT

Originally Posted By David_Hineline:
I am always amazed at the number of people who are clueless on a subject but feel the need to express thier opinion anyway.



Who is clueless?
Link Posted: 9/10/2005 6:15:33 PM EDT
cms81586

Great Post, thanks for the eye opener, we can all use a reminder now and again.
I've never had a slam fine on an AR as yet. Emphasis on YET.

myit
Link Posted: 9/10/2005 8:07:59 PM EDT

Originally Posted By BravoSierra:
anybody remember this one?


Their are two types of people: Those that have had AD's, and those who are about to.



Very true, if you always prepare for them a take the proper measures, follow the 4 basic rules, its a good percentage, everything should be ok.
Link Posted: 9/10/2005 8:17:03 PM EDT

Originally Posted By Ar-15TechGuy:

Originally Posted By steve-oh:
Had to have been the M16 carrier.





If he had a non-modified M-16 firing pin in there it 'may' have contributed to the accidental firing. An M-16 firing pin has a little more mass to it and does tend to smack the primer with a little more force then an AR-15 firing pin. A non-modified M-16 bolt carrier is also more prone to slam fires...
There is a reason that Colt and others have cut and modified the AR-15 bolt carriers near the firing pin. (To help prevent slam fires)



I always thought they threw the notched hammer and cut carrier to prevent the rifle from going full-auto. On purpose or not.

WIZZO
Link Posted: 9/10/2005 10:40:22 PM EDT
It sounds like a slam fire to me. But I'm an idiot.
Link Posted: 9/10/2005 11:45:21 PM EDT

Originally Posted By Epeeman:
You shouldn't be chambering a round unless the weapon is pointed down range!

At the regulated range I go to most often, weapons are pointed down range unless and until they are put in a case to be carried off the line.

I know you are only asking a tech question concerning why this may have happened with your rifle. But it's important and affects all of us since everything any target shooter or hunter does affects public opinion of shooting.

Be safe. Good shooting.



+1 on the good advice.


ps. this must be blue mountain right?
Link Posted: 9/11/2005 2:51:12 AM EDT
[Last Edit: 9/11/2005 2:53:10 AM EDT by j3_]

I always thought they threw the notched hammer and cut carrier to prevent the rifle from going full-auto. On purpose or not.

Caused by the same thing. You do loose a little of the safety designed into the SP1 system of parts by using the "enhanced" style carriers and unnotched hammers. But I have seen SP1 parts not catch the hammer when it should have 100% of the time. I also had a lower not to long age that had the trigger hole drilled .02" to low on the receiver and the carrier did not push the hammer down far enough to catch the disconnector. It caused an occasional slam fire if you held the trigger to long after firing.
Link Posted: 9/11/2005 6:23:23 AM EDT
Most interesting J3_. Can you tell us more?
Link Posted: 9/11/2005 8:55:53 AM EDT

Can you tell us more?

About what?
Link Posted: 9/11/2005 4:43:55 PM EDT
[Last Edit: 9/11/2005 4:44:28 PM EDT by WSAR15]
About this: "You do loose a little of the safety designed into the SP1 system of parts by using the "enhanced" style carriers and unnotched hammers."
I am intrigued about the fact that the enhanced bolts may have left some issues behind.... I'd like to build safer ARs. Also, this would seem to indicated that a heavier buffer may be better than a heavier bolt.
Link Posted: 9/11/2005 4:54:58 PM EDT
[Last Edit: 9/11/2005 4:59:26 PM EDT by pun]
A non modified carrier more prone to slam fires,I guess M16s should be redesigned to use cut carriers then.Not for nothing but I think thats BS larger collar firing pin and full auto carrier makes weight increase minute.I run a 9mm buffer in my rifle and have a shrouded carrier with a notched hammer.No slam fires..and I have never had one in the 13 years I have had the rifle.Maybe the ammos primer was not as hard as it should be or maybe the round had been cycled many times before wich can discharge as the firing pin does make a small dent but so dosent my garand and M14 types....all have floating firing pins.I dont think its the carrier or the pin unless the hammer is riding the carrier as it goes into battery.The notched hammer and machined shroud on the carrier is so the hammer will hang up on the carrier in case the disconector breaks or is removed on purpose.If M16 carriers and firing pins were more prone to slam fires wouldnt something have been done design wise in the last 40 years to correct this.Maybe its the parts or the receiver holes that are out of spec thats causing the problem.Hell Colt sends their carbines with M16 carriers and my L&W conversion also came with one....no slam fires.
Link Posted: 9/11/2005 6:57:31 PM EDT
[Last Edit: 9/11/2005 6:58:15 PM EDT by A_Free_Man]
The firing pin can't project unless the bolt is rotated (in battery).

High primer, it would have popped the primer as the bolt hit it, before the bolt rotated and locked, resulting in a kaboom. You did not have a kaboom, it appears, as you did not mention the mag blowing out of the mag well, the sides of the receivers bulging, etc. It was not a high primer.

A cookoff can't happen immediately, it takes time for the heat to soak in and heat it up to such a temp as to light it off. This is why, after firing a long string, a belt, several mags, you are instructed to open the bolt, eject the chambered round. Besides, you did not fire enough semiauto to get there.

Most likely the hammer bounced off the trigger for some reason. Perhaps insufficient sear engagement. A piece of primer could have fallen into the sear notch preventing full sear engagement. A loose primer could have been down in the receiver, UNDER the rear of the trigger, preventing the trigger from returning to full forward position and thus, full engagement. Or worn sear.

It is in the hammer/trigger area you need to be concerned with. Look at the ejected brass (all of it) for a missing primer.

Questions? Comments? Buehler? Anyone? Buehler?
Link Posted: 9/11/2005 7:51:52 PM EDT
Did you have your finger on the trigger when it went off?
Link Posted: 9/11/2005 8:02:10 PM EDT
I think its George Bush's Fault

Seriously read
What A_Free_Man Said
Link Posted: 9/11/2005 8:17:42 PM EDT

Originally Posted By resq944:
I think its George Bush's Fault

Seriously read
What A_Free_Man Said



Thank you resq944. It is good to know that at least one person here recognizes my genius in such things, even if I do tend to piss off LEO's with my no compromises position on the 2nd Amendment (AND the Constitution and Freedom as a whole).
Link Posted: 9/11/2005 9:03:34 PM EDT
[Last Edit: 9/11/2005 9:05:06 PM EDT by f2]

Originally Posted By A_Free_Man:
...A cookoff can't happen immediately, it takes time for the heat to soak in and heat it up to such a temp as to light it off. This is why, after firing a long string, a belt, several mags, you are instructed to open the bolt, eject the chambered round. Besides, you did not fire enough semiauto to get there...

take out the magazine, open the bolt, eject[ing] the chambered round...
Link Posted: 9/11/2005 9:55:08 PM EDT

Originally Posted By A_Free_Man:

Originally Posted By resq944:
I think its George Bush's Fault

Seriously read
What A_Free_Man Said



Thank you resq944. It is good to know that at least one person here recognizes my genius in such things, even if I do tend to piss off LEO's with my no compromises position on the 2nd Amendment (AND the Constitution and Freedom as a whole).



Wait a second....before you pat yourself on the back, did you get David_Hineline's endorsement of your opinion before posting it??

Otherwise, you're not qualified to have an opinion.

Link Posted: 9/11/2005 10:09:08 PM EDT

Originally Posted By A_Free_Man:
A cookoff can't happen immediately, it takes time for the heat to soak in and heat it up to such a temp as to light it off.

Actually, it can happen almost instantaneously if it's hot enough. As mentioned previously, during a string of auto fire of an M16 with less than 4 30 rd. mags, cook off occured and started the bap.., bap.., bap.. of blanks cooking off. Only taking the magazine out shut that puppy down.

Bueller
Link Posted: 9/11/2005 10:33:29 PM EDT
[Last Edit: 9/11/2005 10:35:50 PM EDT by RRA223]
If your finger didn't pull the trigger, I feel the sear needs a look at. The firing pin rotates in the bolt, can't be a slam fire like M1 garands are known for.
Link Posted: 9/12/2005 12:53:31 AM EDT
[Last Edit: 9/12/2005 1:04:07 AM EDT by j3_]

The firing pin can't project unless the bolt is rotated (in battery).


It is possible for it to fire without rotating into battery. . If the cam pin is left out during reassembly.


Thats why the warning is in the manual. page 2-37


It is good to know that at least one person here recognizes my genius in such things



Wiley Coyote was a genius too.
Link Posted: 9/12/2005 6:51:36 AM EDT

Originally Posted By pun:
If M16 carriers and firing pins were more prone to slam fires wouldnt something have been done design wise in the last 40 years to correct this.



That is a very good point. And for you history buffs the AR-15 (as in Model 01) did suffer excessive "slam fires" in the early 1960's. The fix was a much lighter firing pin.

Even so, with any design there will be instances of a round going off simply by chambering, just a matter of time and use. As pun pointed out, the current design holds such occurrences to an acceptable level.

In this particular case I would not rule out a cook off.
Link Posted: 9/12/2005 12:25:09 PM EDT
Yes, but I have never seen or heard of a cookoff being instantaneous. And as a previous poster pointed out, when they do cookoff, it is bam... bam... bam... bam... , not full auto rate.

The AR was fired before and after without it blowing up... the cam pin was in.

My vote is still with a worn sear (hammer or trigger), or piece of trash, primer, anvil, caught in the hammer/trigger or under the rear of the trigger.

No matter what the cause... this guy showed proper safety, the rifle pointed safely downrange (or up) when chambering a round). I am sure he is not careless, and he engaged in normal operation the same as all of us had. This AD could have happened to any one of us, me, you, any of us. It is not his fault, the manufacturer's fault, the ammo maker's fault. It is the nature of what we are operating.

Learn from this.
Link Posted: 9/13/2005 2:37:22 PM EDT
Forgot to mention that the rnd that went off didn't eject all of the way...it stove-piped in the ejection port. I finished that mag and then dissassembled the rifle. Nothing appeared amiss, and the cam pin was it...(didn't have any extra parts after i cleaned it...). I doubt it was a cook off. The mags I went through before hand were all aimed rapid fire (one shot every 2-3 seconds). I wasn't bump firing or anything. No clue how it happened but just tryin to remind ya'll to stay safe.
Link Posted: 9/13/2005 2:46:15 PM EDT
It is just possible to have a slam fire sometimes. The chances are extremely minute, but the chance *is* there. That's why I've argued in other threads against storing your gun with the bolt locked back and a magazine inserted. If it gets jarred and the bolt slams home it might slamfire. I know the chances are extremely low, but it would suck if you were the one guy to get killed by your own gun sitting on the other side of the room.
Link Posted: 9/14/2005 3:04:44 AM EDT
[Last Edit: 9/14/2005 4:07:37 AM EDT by f2]
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