I was was out earlier today doing some plinking with my AR and I fired five shots, inserted five more rounds in the magazine, fired one shot, when I pulled the trigger the shot did not sound right, three rounds fired when I pulled the trigger. I fired about ten more rounds with no issues, what would cause this issue.The upper was built by a local who builds AR's and the lower is built on an Anderson frame, also built by a local guy.

Thats usually a clue for questionable work. Let someone who knows what they are doing (a gunsmith, not some random guy slapping AR's together with cheap parts) replace your trigger or install it correctly.

Its very easy to do if you want to tackle it yourself. Watch the video below.

http://www.brownells.com/GunTech/Brownells-How-to-Install-An-AR-15-M16-Trigger/detail.htm?lid=16175

Could be light or not fully seated primers. The floating FP can contact with sufficient force to set of soft primers.

if BATF monitors the 'fire, look for a visit soon.

What is the currently installed trigger?

Stock? Aftermarket? Adjustable Target?

Were you shooting handloads? If so, what kind of primers were you using?

Federal primers have done that to me a time or two recently. I had heard that they would but did not have that experience until the last couple of months. The entire line went quiet. So did I.

I'd look at the trigger assembly first, ammo second.



Travis

If you are running an M16 bolt carrier, it could be the trigger. If not, I'd suspect ammo.

I had one that double/triple tapped once when I forgot to put one the little springs in the trigger assembly. Of course I fixed it promptly and would never consider altering the trigger assembly in the future.

I was shooting handloads,I was using win small rifle primers, they are older primers, white box, not current manufactured primers. Went our earlier today and shot some rounds with no issues.

I've shot a lot of Federal primed .223's out of several AR's with no issues. It's only recently that I've had a couple instances of auto-fire. Not a comfortable thing. I simply won't be priming with Federal's anymore, except for a brick I bought about a year ago that are specifically for AR's. I think those will be OK. If I were you, I'd use something other than what you used when the auto-fire happened. CCI #41's are probably what I'll use after the Fed AR primers are gone, but I'm also going to test a hundred before I load the rest of those.

I've seen an AR with a 3lb CMC trigger do some double-taps when fed a certain ammo (62gr green tip), yet it did not do it with other ammo. And yes, it is a bit disconcerting....

check your trigger disconnector

Winchester small rifle primers.

That's your problem.

Winchester primers have the softest cups. If I have a gun suffering from light primer strikes, I switch to Winchester primers.

On the other hand, you should not feed our AR's with Winchesters primers. I feed mine CCI, which have the hardest cup material. 400's for stick powders, 450's, or 41's for ball powders, and BR'4's when it that's what a particular combination likes.

If you absolutely have to use Winchester primers, replace your firing pin with one made out of titanium.
It should lessen the chances of slam fires.

RE ww primers, if they are brass color they are soft. If silver they are some of the hardest out there...

TI pin... first time you pierce a primer you have a really expensive paperweight... FWIW.

The issue can be as simple as too light of a trigger. Anything 3.5 pounds or so or less, thats not 2 stage, generally speaking, can give issues.

And some of those are related totally to how the gun is held, how it recoils and how you hold/pull/reset the trigger...

Thin cupped primers are not your problem. Think about it, how often do you hear about slam fires with the gold WW primers or Federal? Not very often yet you think he had 3 right in a row? Not happening. I've heard of 2 or 3 and rost was the one who told about those.

I've fired thousands of Fed 205Match primers and gold and silver WW's without ever having a problem. And that's with heavy buffers.

Bad disconnector or trigger is set too light.

Rost, I have a good supply of silver WW's circa Y2k and they are very soft. Same for the new silver WW pistol primers I bought.

Did the specifically harden the cups on their small rifle primers, because I haven't noticed it on their large rifle, pistol, or shotgun primers?

I was using the older manufacture silver colored primers, I won't use the gold colored ones.

Silver is supposed to be some coating... nickel? Harder than without. Never saw a single issue with a silver WWSR primer.

I have personally had 2 slam fires, singles, with Fed SR primers. Wont' use em again. YMMV.

I've spoken with folks about the new brass colored WWSR that have seen a slam fire or two, these folks are no less than national champions in the game.... I trust them in other words.

Life is to short, to many choices of primers, to choose ones that MIGHT create an issue.

Guess with TWR, same could be said about cheap lowers. LOL.

But a slam fire costs me teh match. Won't risk that.

But no, I cannot at all see 3 slam fires in a row.

Which AR??

Does it have three positions on the safety?

did a guy that goes by the handle Renegade50 hone your trigger for you? He lubricates "everything" with spit so if there are any tobacco spit stains in your gun it was his work.