Ok, so I have a normally perfect functioning RRA. The other day as I was shooting the thing it turned full auto on me (not by design). Upon diasassembly I found the cam pin and the firing pin retaining pin both were broken. Care to speculate what might have been the cause.

broken how?  Like, in half?

As MarkM would say.   "These things happen".  The cam pin is a part you are supposed to inspect regularly for cracks and replace as needed.  Ok yours broke, replace it and move on.

Quoted: As MarkM would say.   "These things happen".  The cam pin is a part you are supposed to inspect regularly for cracks and replace as needed.  Ok yours broke, replace it and move on.

Why do some people think just because you ask a question you are somehow complaining? When I asked my original question, I was not whining. Yes I have replaced it and moved on. My question was and still is, any ideas what might have caused the cam pin to shear in half and break the firing pin retaining pin. How would this cause the weapon to go full auto. I assume the firing pin was somehow trapped forward but still don't understand the the mechanics ivolved.

Don't get all twisted sister, Cleatus!  So you have an Illegal Machine Gun!

ENJOY IT!

Why do some people think just because you ask a question you are somehow complaining?  

Thats just something you have to get use to around here. Seems like there are a handful of folks here who just lurk for the chance to jump down someones throat. Its a shame they cant just answer the questions people have without jumping thier ass.  Seems like most of the ones who do this are the ones with mega high post counts, wonder how many of those post were productive.  Good luck with your problem I just had to jump in cause I have seen this too many times.

Quoted: Why do some people think just because you ask a question you are somehow complaining?   Thats just something you have to get use to around here. Seems like there are a handful of folks here who just lurk for the chance to jump down someones throat. Its a shame they cant just answer the questions people have without jumping thier ass.  Seems like most of the ones who do this are the ones with mega high post counts, wonder how many of those post were productive.  Good luck with your problem I just had to jump in cause I have seen this too many times.

+1 batrillion

Quoted: Quoted: As MarkM would say.   "These things happen".  The cam pin is a part you are supposed to inspect regularly for cracks and replace as needed.  Ok yours broke, replace it and move on. Why do some people think just because you ask a question you are somehow complaining? When I asked my original question, I was not whining.

Why is it the newbies all have a chip on their shoulder and scream 'foul' at any post that doesn't hand hold them through everything?

Nobody assumed you were complaining - though from your reflexive response I may have to think you were.

As I said - IT HAPPENS - it a normal part that needs to be inspected for stress cracks.  Because if you don't inspect for them or don't find them the parts can crack on you.

I've never heard of one going full-auto,  but rifles missing cam-pins have 'Kboom'ed. Be thankfull you didn't have one of them.

Quoted: I just had to jump in cause I have seen this too many times.

Thanks, Mr. Helper!

Look!  Sometimes we rough up the new guys a little.  It's not meant to drive them away.  It's just a healthy initiation.  A lot of guys don't have the balls to handle it.  And it's good to know who you don't want to end up fighting next to you....  Both figuratively and literally!

w00t!

This is why I stress “Cleaning like the Drill Sgt taught ya!”

Many folks don’t seem to think that a thorough cleaning/inspection is needed. “You’ll ruin your rifle sooner over cleaning it as opposed to shooting it” is often preached here. Regardless of the round count fired I maintain my rifle the same each and every time. Cleaning is not a pain in the ass to me but a way to possibly catch problems before they rear their ugly head at the range. The Army calls it PMCS, Preventative Maintenance Check’s and Services. It’s all called out in the Technical Manuals and Field Manuals but often over looked by civilian AR15 owners.

I’m not calling you out on your cleaning procedures, merely raising the point that correct cleaning and inspection procedures can often catch things like a hairline crack in a cam pin hole.

Quoted: Quoted: I just had to jump in cause I have seen this too many times. Thanks, Mr. Helper! Look!  Sometimes we rough up the new guys a little.  It's not meant to drive them away.  It's just a healthy initiation.  A lot of guys don't have the balls to handle it.  And it's good to know who you don't want to end up fighting next to you....  Both figuratively and literally! w00t!

+87...

It's just "tough love".

Sly

OK. I'm a big boy. Balls I got. No problem there. Still, noone has offered any constructive ideas why the thing went full auto. The whole original intent of this post was to see if anybody had ever seen these two parts failure cause a weapon to go full auto. I understand the potential problems associated with a cam pin malfunction but have never heard of full auto as a side effect. My only thought is possibly the broken firing pin retaining pin somehow trapped the firing pin forward and in affect caused a series of slam fires. Don't know how the cam pin comes into play. Now, for all you old timers who enjoy taking shots at us "newbies" (new to this sight only) go right ahead. It's actually rather enjoyable to see what your going to come up with next.

OK.  That's a tough one!  I haven't read about that problem in the years that I've been here, but if it has happened elsewhere, someone will chime in with some info.

Quoted: ..Still, noone has offered any constructive ideas why the thing went full auto. ...

I thought about this over lunch.  

I was leaning toward the idea you have - that the broken cam pin jammed the firing pin forward and your rifle was slamfiring.  Since you have a RRA, the bolt carrier should be the shrouded type.  As such the hammer WILL NOT catch on the firing pin during a slam fire and you can get a 'full auto' type of situation.  (the ramped carrier and big ring on the semi-auto firing pin were meant to catch in the notch of the hammer face in the event of a disconnector failure to prevent slam fires - and to prevent people from pulling the disconnector to try to get simulate full-auto via the hammer following the firing pin down).

The only problem with this theory is the bolt was still sliding (piston like) in the bolt carrier - i KNow this otherwise the bolt would not have turned to unlock and you would not have ejected the old rounds and fed in the new rounds.  Now with the bolt in the full forward position the firing pin cannot protrude through the firing pin hole (it's not long enough).  The firing pin can only protrude when the bolt is all the way back (firing position).  So the firing pin is obviously not locked into position.

Did the fragments grab onto the firing pin as the bolt slid back (kind like a cam lock) to only hold it then?

Or if the firing pin - now free of any friction from the cam pin - have enough momentum to to fire the round as the bolt carrier slid home (slam fire from the firing pin)?  Were you using mil-surp or commercial ammo?

I think that would require some high speed x-ray photography to find out for sure.

Of course there is the third option.  Something else was going on with the rifle (worn disconnector or some such) that just happened to occure about the time your cam-pin broke.  Have you taken the rifle back to the range since replacing the cam-pin?

Quoted: Quoted: ..Still, noone has offered any constructive ideas why the thing went full auto. ... Of course there is the third option.  Something else was going on with the rifle (worn disconnector or some such) that just happened to occure about the time your cam-pin broke.  Have you taken the rifle back to the range since replacing the cam-pin?

Would the broken cam pin and firing pin retaining pin be a product of the malfunction, and not the cause?  I would think the disconnector failed and then the slam firing resulted in a couple more broken parts.

Quoted: Quoted: Quoted: ..Still, noone has offered any constructive ideas why the thing went full auto. ... Of course there is the third option.  Something else was going on with the rifle (worn disconnector or some such) that just happened to occure about the time your cam-pin broke.  Have you taken the rifle back to the range since replacing the cam-pin? Would the broken cam pin and firing pin retaining pin be a product of the malfunction, and not the cause?  I would think the disconnector failed and then the slam firing resulted in a couple more broken parts.

I was thinking of two independant failures at the same time.  I can't imagine firing a few rounds on full-auto would damage the parts - after all M4s fire bursts/auto all the time w/o breaking cam pins.  

But it's as good a guess as any.

So now there are 4 possiblities?

Just a side note here, don't ever put your AR back together without the firing pin in it.   There is a chance that the cam pin can then rotate so that the bolt won't unlock.

This is not a good thing.

A buddy of mine called me one night to tell me he had done this.  I was really impressed; it went way beyond amateur hour stuff like charging the weapon with the buffer and buffer spring missing or getting a Q-tip broken off inside the gas key.

Quoted: Just a side note here, don't ever put your AR back together without the firing pin in it.   There is a chance that the cam pin can then rotate so that the bolt won't unlock. This is not a good thing. A buddy of mine called me one night to tell me he had done this.  I was really impressed; it went way beyond amateur hour stuff like charging the weapon with the buffer and buffer spring missing or getting a Q-tip broken off inside the gas key.

Screw you.

Have you taken the rifle back to the range since replacing the cam-pin?
Both parts were replaced and the weapon once again functions perfectly. (As for the slam fire theory, the rifle cycled every round but the last. The last round was still in the chamber and displayed a small dimple on the primer.) I think I might chalk this whole thing up to voodoo.
Out!

Quoted: This is why I stress “Cleaning like the Drill Sgt taught ya!” Many folks don’t seem to think that a thorough cleaning/inspection is needed. “You’ll ruin your rifle sooner over cleaning it as opposed to shooting it” is often preached here. Regardless of the round count fired I maintain my rifle the same each and every time. Cleaning is not a pain in the ass to me but a way to possibly catch problems before they rear their ugly head at the range. The Army calls it PMCS, Preventative Maintenance Check’s and Services. It’s all called out in the Technical Manuals and Field Manuals but often over looked by civilian AR15 owners. I’m not calling you out on your cleaning procedures, merely raising the point that correct cleaning and inspection procedures can often catch things like a hairline crack in a cam pin hole.

+1 I do this ever single time I shoot. If I see a questionable item such as a spring feeling too mushy I toss it right there and pull a new one out of the parts box and move on. My last cleaning I changed the ejector spring.

From all the reports of broken/worn parts I have seen on this site I look closely at:
Cam pin
Bolt
firing pin retaining pin
gas key

and in the lower I take a quick look at the fire control group for general operation and "feel".

you may want to do the same, it will save you time and heart ache / frustrations in the future.

ETA: full auto issue could be a bad disconector. It happened to me twice. I keep a few on hand for replacements.

One last thought occured to me.

Were you shooting reloads or factory ammo?