A friend of mine said that AR's are notorious for slamfireing. Is this true?

Not notorious but I've heard it can happen to nearly any semi auto firearm. I've never seen this happen to an AR-15 and I have never met anyone who it has happened to while shooting an AR-15 and I have been around these rifles for nearly 20 years. Notorious? Hardly. Possible? definitely. Practice safe firearms handling such as loading the rifle while pointed in a safe direction and you may someday be surprised but you will avoid a tragedy. Also beware of reloads. Not that they can't be used, but be sure they are made by a trusted expert.

Your friend doesn't know as much as he seems to think he does, IMHO.  

In near twenty years of competition, it's never happened to me, and I've never seen it happen.  I've HEARD of it happening, and it's theoretically possible, especially with a poor reload having a high primer, but I'd scarcely call that "notorious".

If you lock the bolt back, drop a round in the chamber, and hit the bolt release, then eject the round without firing, you'll see a faint indent on the primer.  (On most AR's)This is due to the inertial firing pin, which has no spring, as most semi-autos do.  It's normal, but it makes some folks nervous.

Well, there's nearly 40 years combined experience. That should answer your question.
Have no fear, only respect.

Any semi can slamfire, but ARs are one of the least likely to do so. Now M1s and M14s . . .

ARs are not "notorious for slam-firing" but it is possible to experiece one given the "floating" firing pin.
Best advice: point your AR in a safe direction whenever you chamber a round. Odds are you'll never have trouble, but better to be safe than sorry.
There's lots of good info over at www.fultonarmory.com
in particular look at their AR-15 FAQ section. Here is what they have to say about Slamfire in ARs:

"May I commend to your attention pgs 123-133 of Ezell's "The Black Rifle," where the "premature" or "indadvertent" firing problem with the M16 is discussed at some length. The solution taken was one of the "Eleven Pre-Production Modifications" on pages 135-136, to wit:

"5. Firing pin redesign (fig. 138)

"Finally incoporated as part of the TCC's "field fix" for the inadvertent fire problem, in conjuction with the adoption of less sensitive primers. After attempts by Colt's and Springfield to spring-load or otherwise partly restrain the firing pin, it was finally agreed to use a Colt idea which simply lightened the firing pin's total mass, thereby decreasing the force of its "bounce" off the primer." (emphasis added).



Figure 138: Firing Pin Redesign

On page 148 Stoner is quoted as saying: "Either desensitize the primer, make it out of a thick material, or lighten up the firing pin...I recommend...lightening up the firing pin because...if you desensitized the primer too much it could cause failures to fire in the field."

Yes, the locking lugs should be engaged for the firing pin to reach the primer, much as in the Garand-type action (M1, M14). However, a "Slam Fire" is simply the condition when a round is discharged without the normal firing mechanism being employed. Slam Fires may be caused by a broken/protruding firing pin, foreign matter on the bolt face, firing pin intertia, or other means. A Slam Fire may occur *in* or *out of* battery. In the first case, we have a truly Accidental (in contrast to a Negligent) Discharge with little or no potential harm to the shooter. In the latter, the breech is unlocked and *very* bad things can happen.

To be truly pendantic, there are those firearms that depend on "slam fire" for functioning, typically subguns such as the M1A1 Thompson. The firing pin is a bump on the bolt face.

In conclusion, where M1s, M14s and M16s are concerned, lighter firing pins are better, and use Mil-Spec primers. Hey, we spent a lot of tax dollars finding this stuff out!

--Walt Kuleck"

Thanks to Fulton Armory for the text-
I suggest you give their website a look.

To follow up on Gonzo’s post - the military found that the very first AR-15’s did have a slam fire problem when a round was manually seated in the chamber and the bolt allowed to slam forward.  As he mentions, this was solved by lightening the firing pin.

Even today, loading semi-autos like that is generally a bad idea.

Also, keep in mind that slamfires (or what appears to be slamfires) can be caused by a badly worn or fiddled with trigger mechanism that slips when the bolt slams forward.

(And what’s this idiot doing pointing a firearm at his dog anyway – practicing dog hunting??)

Just curious....how do you clean it?  How do you know when it's time to replace gas rings?

Yes, AR's can slam fire.  Happened to my shooting partner this year at Perry in the middle of a slow fire string.  Nobody around him had ever seen it happen.  The Marine armorers were perplexed.  The civilian armorer was perplexed.  But it most definitely did happen.  No damage done.  

When i was in the Marines some of my friends would go full auto on the range and say it was slam firing. Never actually saw a slam fire then or since but sure it can happen.

Guys,

I "think" I have a AR that has slam fired several times now.  But maybe it hasn't.  You all be the judge.

BM lower I built (yes, it is possible I am responsible in some way).  Franken upper with 16" bull barrel and FN flattop.

The trigger is a RRA NM.  ACOG sight.

OK, normally this is a sweet shooting rifle.  But every once in a  while it thinks it's an M16.  Only for a few rounds, but a bit disconcerting when it happens.  (Would be cool if it would do it when I want it to).

I have noticed it only happens with Federal civilian ammo.  Never with military ammo.

OK.  Is this slamfire or a trigger problem?

James

The SKS will slam fire if you dont clean the cosmoline out of the firing fin area.   Thats how some sorry bastard shot himself in the throat, when he panicked and dropped it.(allegedly)   Anyone else heard about that one?  

The SKS will slam fire if you dont clean the cosmoline out of the firing fin area.   Thats how some sorry bastard shot himself in the throat, when he panicked and dropped it.(allegedly)   Anyone else heard about that one?  

Maynard - this is no flame - I hope you aren't using your rifle as a weapon - whether or not you are, I suggest that you rtfm and clean and lube the rifle properly.  Good luck.

Tate

troy and striker,

Sounds like you both agree with the problem.  I have suspected the trigger.  When it happens, I can feel the trigger pulsing under my finger.  And I know it is not supposed to fire again until I release the trigger and it resets.

It hasn't happened lately, so I am wondering if it worked itself out.  As I "always" follow safety first, I am not concerned with slamfire or whatever.  I will continue shooting it.  If it happens again, I might give RRA a call to see if they want to replace the trigger.  I installed it, but I can't see how I could have screwed it up.  There isn't much adjustment or options with their trigger (which BTW I do like).

James

I have witnessed no slam-fires (dropping bolt and having discharge), but on 2 occassions w/ CR 6724 match type rifles, using Rem 7.5 Benchrest primers, have seen doubles (attributed to not 100% fully seated primers). The last time w/ Uncle's gun he put 2 rounds in under 3" at 800 yds. I decided to put a Titanium firing pin in mine, and weighed it against the stock pin - it was 43% lighter. I have had no subsequent problems.

Been around military ranges since the late seventies and have never witnessed a slamfire.  Fired multi-thousands of rounds through my three ARs and no slamfires.  At last month's local high power match the top (local) shooter had a slamfire.  Consider that he wasn't using anything close to a service grade AR and was almost certainly using his own handloads.  I didn't get to speak with him, so I have no idea what the cause may have been.

Eddie