AR- Stupid question


PDA






kestak
July 10, 2009, 01:47 PM
Greetings,

AR type actions have a probability of slam fire. What is the reason they did not put a spring on the firing pin like the old Russian SKS?

Thank you

If you enjoyed reading about "AR- Stupid question" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!
rcmodel
July 10, 2009, 02:01 PM
Probability of fouling & dirt stoppages, and broken springs.
The large majority of SKS, and all AK's do not have a spring either.

Actually the AR system has a zero probability of a dangerous slam fire causing a blow-up.

The firing pin can't even reach the primer until the bolt carrier collapses on the bolt and locks it into the barrel extension.

The tiny primer dings you see on loaded rounds has been addressed by mil-spec primers being harder then commercial primers.

It's actually a non-issue.

rc

RH45
July 10, 2009, 03:58 PM
I see slam fires at 3-gun matches all the time with ARs, but, I've never had one myself.

rcmodel
July 10, 2009, 04:16 PM
Slam-fires?
Or bump-fires from the light triggers & short re-sets the three-gun guys are using?

The fact remains that whatever you are seeing didn't cause the AR's to blow up did they?
If they were true slam-fires before the bolt was locked, the guns would blow up.
But they didn't.

rc

FlyinBryan
July 10, 2009, 04:19 PM
i reload and have intentionally seated primers flush to see if i could induce one (most reloaders recess the primers around 3 thousandths or more)

couldnt make it happen, even though the primers had been struck a little deeper than normal reloads.

like mentioned above, its really a non issue

kestak
July 10, 2009, 04:20 PM
Greetings,

Excuse my ignorance. I though slam-fires are occuring when the bolt reaches the end of its course and the firing pin inertia makes it hit the primer. Wouldn't the bolt be locked at that time?

Thank you

rcmodel
July 10, 2009, 04:35 PM
There are out-of-battery slamfires, and that's what the SKS firing pin spring was designed to address.

There are also in-battery slam fires, and the only result is the weapon fires a round without pulling the trigger.

As I already noted, it has been addressed in the AR-15/M16 system in a different way then using a firing pin spring.

AR slam-fires just don't happen with proper commercial or GI loads, or properly assembled hand loads.

Doubling or bump-firing is usually a result of trigger mods by someone that shouldn't have.

rc

taliv
July 10, 2009, 04:38 PM
AR slam-fires just don't happen with proper commercial or GI loads, or properly assembled hand loads.

BUT there is no guarantee that the next commercially loaded round you chamber was properly assembled. Accidents happen. ALWAYS keep the muzzle pointed in a safe direction.

ChCx2744
July 10, 2009, 06:27 PM
What if the bolt did not go forward all the way and was stuck back a bit too far when you charged it that when you pushed the forward assist, it sent it foward far enough to slam fire it??? HUH HUH HUHH??? :neener:




..no really though, what if...? :uhoh:

ace88
July 10, 2009, 07:05 PM
A similar discussion came up at another board. I put chalk on my hammer and let it fall, with the bolt slightly out of battery. The picture is not very good, but you can see where the hammer hit the carrier. I'm not saying that an AR won't slam fire, I just posted this to show that the hammer can't fall on the firing pin when out of battery.

http://img.photobucket.com/albums/v472/millwright/PICT0150.jpg

Whitman31
July 10, 2009, 09:41 PM
A poor trigger job having a malfunction and a true slam fire are two very different things. Using the charging handle to close the bolt doesn't generate enough momentum in the firing pin to cause a slam fire. Even a poor trigger job would have to be "really" bad for this to happen. The trigger would have to remain cocked and the fall off of the sear with the small "jar" caused by banging the charging handle. This would mean that the gun could theoretically go off at anytime.

+1 with what RC said about this whole topic...

marsche
July 10, 2009, 11:31 PM
Slam fires can be an issue in an AR because of the way the system is designed with a free floating firing pin. When the bolt moves forward and locks the firing pin inertia makes the pin hit the primer. To test the possibility - load a magazine and stick it in an AR, pull the charging handle all the way back and let it go. Eject the round that you chambered and look at the primer. The primer will display a small dent. That dent is caused by the firing pin continuing forward after the bolt abruptly stops.

The argument that a firing pin spring is not used in an AR because it is "addressed in the AR-15/M16 system in a different way" is not totally true, if the 'different way' is in hardened primers. Many high power shooters reload for the AR and for the Garand. Two things many of them do to avoid slam fires are to uniform the primer pocket making it slightly deeper and using hardened military primers. However, not all reloaders are as careful or as knowledgeable. So, the answer is yes, an AR is prone to slam fires and you have to take precautions to make sure it does not happen. That is, you have to reload with slam fires in mind.

taliv
July 11, 2009, 12:15 AM
ace88, i applaud your willingness to actually TEST things

but note that your carrier has what is called a "shrouded firing pin" while many if not most carriers sold by companies like RRA/DPMS/etc have the rear of the firing pin exposed so that it IS possible for the hammer to hit the pin out of battery. (though that wouldn't cause an OOB incident, since the firing pin itself is not long enough to reach the primer when the bolt is OOB

SHvar
July 11, 2009, 01:41 AM
Actually most if not all manufacturers use the standard unshrouded AR SA bolt carrier, some offer a FA (M-16) shrouded bolt carrier as an option or a few models have it standard (very few). No single manufacturer uses a shrouded FA M-16 bolt carrier on all models.

ace88
July 11, 2009, 05:58 AM
ace88, i applaud your willingness to actually TEST things

but note that your carrier has what is called a "shrouded firing pin" while many if not most carriers sold by companies like RRA/DPMS/etc have the rear of the firing pin exposed so that it IS possible for the hammer to hit the pin out of battery. (though that wouldn't cause an OOB incident, since the firing pin itself is not long enough to reach the primer when the bolt is OOB

Actually most if not all manufacturers use the standard unshrouded AR SA bolt carrier, some offer a FA (M-16) shrouded bolt carrier as an option or a few models have it standard (very few). No single manufacturer uses a shrouded FA M-16 bolt carrier on all models.

That is true. I would advise anyone that has a unshrouded AR15/SA bolt carrier, to replace it with a quality M16/FA bolt carrier group made by Bravo Company Manufacturing, or Lewis Machine and Tool. That's just my $.02, That's one reason that I built my AR, so I could put what ever parts that I wanted into it.

rskent
July 11, 2009, 06:44 AM
Kestak

If you single load an AR, such as in a highpower match or shooting
off the bench to work up loads, there is a chance of a slam fire.
Just point it downrange when you drop the bolt and you won’t
have a problem.

Keep it safe.

Steve

MisterPX
July 11, 2009, 09:05 AM
if the AR is "prone to slamfires", then damn near every other modern semi auto rifle is "prone to slamfires". ;)

Heck
July 11, 2009, 02:36 PM
I have heard that forgetting to install the diconnector spring can be bad.

If you enjoyed reading about "AR- Stupid question" here in TheHighRoad.org archive, you'll LOVE our community. Come join TheHighRoad.org today for the full version!