New AR15. Dangerous?

There's probably a reason why someone left the ammo on the ground. I wouldn't use it in my gun.

AR15s have free floating Firing pins. They will all leave that dimple on the Primer. it is nothing to worry about.
You should not be cambering and rechambering rounds however. Load and shoot

You should not be cambering and rechambering rounds however. Load and shoot

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Sure, generally good advice, but I hunt with two different ARs, and I don't wait until I see a game animal to chamber a round. I chamber a round as soon as I get to my hunting site. But if I don't shoot anything by the end of the day, I don't fire off that round--I unload it and save it for later.

To answer the original poster's question, though: as taliv and kewlz have said, the AR15 has a free-floating firing pin. In other words, there's no spring holding it back until the hammer hits it. It will always bounce a little when chambering and cause that tiny dent, but it's not enough force to ignite the primer. Of course, you should always have a firearm pointed in a safe direction when you chamber it, no matter what type of firing pin it has, just in case it accidentally discharges because of a stuck firing pin, etc.

But a previously chambered round is safe to chamber again and fire...

except that you shouldn't be shooting ammo you find on the ground, as a rule. Store bought, your own reloads, or a trusted friend's reloads, sure. But that round laying on the ground may have any number of problems that could damage your rifle and your body.

Aaron

12Pump said:

Duly noted. I'm really surprised that denting like this is acceptable. That is, in fact what sets off a round--when the firing pin strikes it. It would seem to me that this should not be happening when the trigger is not being pulled to fire the round. None of my other guns do this.

Ok, so what if you chamber a round, decide not to use it, eject it, then load it again? Would that dent it further? It seems like it would only be a matter of a few times of doing that before an accidental discharge would be inevitable.

As for "always have a firearm pointed in a safe direction when you chamber it", inside of a house, I don't want any chance of having my gun go off. I got this particular gun for HD, so when I load it up, I don't want it going off at all, no matter the direction of the muzzle.

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If you chamber a round and don't use it, simply don't load it for potential defensive use again. Use it at the range or in some situation where a misfire (it becomes less likely to fire as you chamber it multiple times) isn't a big deal.

I don't think a slam fire is any more likely than on any other firearm.

Many firearms have free floating firing pins.

And you should point every gun in a safe direction when chambering a round (well, ALL the time, really, but an especially safe direction when chambering a round), this isn't just an AR thing.

12Pump said:

I thought combat type guns had firing pins that were locked into position so that they don't have an accidental discharge if the gun were dropped or bumped hard. AR15 would certainly fall into that category.
This free floating firing pin thing really surprises me!

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Take the firing pin out and take a look at it. They are light. Not near enough mass to cause a slamfire. The only way that can happen is if something has jammed the firing pin forward.

If those dents make you squeemish, buy mil-spec Lake City 5.56 (provided your rifle is chambered for 5.56). Remember your 10 commandments of firearm safety, and shoot it.

That is a Federal cartridge, and I assume it's a factory load but no way to know for sure. However, it is commonly known that Federal primers are the softest made, and generally thought not to be the best primer choice for firearms with free-floating firing pins. Dents like you show are not at all uncommon with Federal ammo. If you want to be the safest you can be with your AR, try to pick up military surplus LC or Winchester or Remington ammo, usually made with harder primers, or load your own.

As an aside, if you reload, you will never be in your current position of not being able to find reasonably priced ammo.

12Pump said:

I thought combat type guns had firing pins that were locked into position so that they don't have an accidental discharge if the gun were dropped or bumped hard. AR15 would certainly fall into that category.
This free floating firing pin thing really surprises me!

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Your concerns are unfounded.

Don't worry about it.

If you chamber a round out of a loaded magazine, the bolt carrier is slowed by friction enough the dents are within acceptable limits with hard military primers or commercial 5.56 primers.

If you drop a round in the chamber and dump the bolt release on it?
Not so much.


As for floating firing pins in military rifles & pistols?

Check out the .30 M1 Carbine, M1 Garand, Russian SKS & Makarov, and any number of other military designs.

Floating firing pins are way more reliable when dirty then those with locks or tiny retractor springs.


What surprises me is that anyone would pick up ammo they found on the ground at a range and try them in a brand new rifle, before they even knew if it worked right or not.

That's just wrong on too many levels to explain it all to you tonight!!

rc

rcmodel said:

What surprises me is that anyone would pick up ammo they found on the ground at a range and try them in a brand new rifle, before they even knew if it worked right or not.

That's just wrong on too many levels to explain it all to you tonight!!

rc

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SO MUCH THIS ^

Frankly, I think that's just plain stupid. For all you know some jerkwad reloaded that round with a double charge of powder and left it there.

I see that this round appears to have sealant around the primer which probably means it is a factory round (I think?), but you never know.

I strongly recommend you NOT shoot any random ammo you find at the range.

Every round I've ever chambered and extracted without firing in an AR or M-16 had a little ding on the primer. It's normal.

Good info on found ammo. Before I knew better I would buy any ammo this storage locker buyer had for sale. Sometimes new. Sometimes loose reloads. I did ask on a gun forum and was told not a good idea to shoot found reloads. Ended up selling it all off to a guy that reloads and he just recycled the components.

12Pump said:

Ok, I won't shoot any ammo I find at the range. I only did it this time because it's all I had.

As for the dented primer thing (which is my main concern here), it's the chambering of the first round and having the potential of going off that scares me the most. Otherwise, during shooting, the worst that could happen is that it "doubles", in which case the gun is already at a range pointed in a safe direction, unlike when I would be at home chambering a round to ready it for HD use. Would it be good to just "ride the charging handle" home so that it doesn't chamber the round so quickly? That would keep the firing pin from flying forward, but would it allow the round to chamber fully?

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You are worrying about a non issue. Riding the charging handle home will lead to malfunctions.

12pump, compare the dimples on the primers of your fired and unfired cases. See how much deeper the dent on the fired primer is? That dimple is completely normal. It's part of how the AR-15 works. If this was a problem, andAR-15s just slam fired all the time they wouldn't be the most popular rifle in America.

On deployments I have chambered the same rounds over and over again. They all went bang on demand when the time came. I'm sure that rechambering the same commercial round with a soft primer too many times could eventually push the primer compound away from the anvil resulting in a dud round, but I think this problem is largely academic. Most people wouldn't be chambering a single round that many times, if it's even a problem at all.

In summary, your rifle is fine. Don't shoot mystery ammo if you value your fingers, eyesight, or gun.

"Every round I've ever chambered and extracted without firing in an AR or M-16 had a little ding on the primer. It's normal"

Well, no...it's not.

Some primers are demonstrably harder than others; but I'm sure we'll agree that rechambering a given round several times, no matter the semi-auto config, isn't a safe practice. Eventually, the dimple becomes deep enough to light the round...and that is an excellent reason for rotating your "used" cartridges with new ones.

Top off that mag with something brand new.

I don't want to see a dead horse get beat here, but part of the reason that the "found round" thing keeps getting brought up is simply because that is more of a safety concern by several orders of magnitude than the dented primer. I know that dent is a little disconcerting, but as the last word on this subject, don't shoot rounds you find laying around.

I am closing this because the OP has had his question answered and been informed of his safety error by almost everyone in this thread.