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458 socom slam fires

10K views 32 replies 16 participants last post by  snowsnake  
#1 ·
If I load a round in the chamber and close the bolt the weapon will slam fire when on safe. It will not do this if it strips one off the mag and chambers it. Where should I start looking to cure this?
 
#5 ·
It's going to take some more details to troubleshoot this.
Maybe even some dry fire testing, upper removed and with a dry fire block, or dropping the bolt on a dummy round.


Does this have a milspec single stage trigger?
Disconnector spring?
 
#6 · (Edited)
Maybe I am not understanding the situation. Are you single loading a round in the chamber then dropping the bolt from the bolt hold open position? I cannot think of any scenario where that would be considered a safe action to take. Not only do you risk slamfire but also risk a broken extractor. If you want to single load the round then ease the bolt closed and bump the FA to ensure it is fully into battery. Now if the latter is what your are doing and it is slam firing then you definitely have a problem.
 
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#8 ·
I had my only slam fire with an AR-15 458 SOCOM while placing a round in the chamber and allowing the bolt to slam forward.
It happened at the range and hit the ground about 10 feet in front of me. This was a light load.
I don't do this with any cartridge anymore.
I recovered the bullet.
 
#9 ·
I tossed a round in the chamber and hit the bolt release on an occasion when I was testing a particular round for accuracy and didn't want it to strip a round because I wanted a cold bore each shot. BANG . My thoughts were the bolt fly's forward a lot faster when it is not stripping a round from mag which gives the firing pin more inertia . My weapon was clean and lubed properly . From then on I load single rounds as Woodstock suggested , slow and easy.

Sent from my Moto E (4) using Tapatalk
 
#10 ·
Exactly, plus when it its stripping it from the mag (as it was designed to do) the bolt is basically right up against the round instead of flying towards it from several inches away.
 
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#11 ·
I am very surprised that there are not more posts like this. A number of factors are involved, first is the far softer standard large rifle primers used with the 458 SOCOM, mix in a steel firing pin that is slightly on the heavy side and viola, a UD upon chambering.

There are many individuals that run a sled follower and singularly chamber their long nosed .223 rounds, no stripping the round from the mag, just letting the bolt fly home and I have never heard of a UD under those situations.

For the original poster, upgrade to a Ti firing pin and search for a harder primer, I know there was a post somewhere with the measured thickness and hardness of all the different primers out there. I went thru a similar issue with my 375 SOCOM and was able to address it with just the Ti firing pin. That should address your UD issue as well, but still treat every chambering as if it will UD and keep the muzzle pointed in a safe direction.
 
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#14 ·
Greg,
Thanks for your post.
I might have 1000 sled rounds fired and I'll read a bunch about slam fires then I'm concerned.
I can ride the bolt with my side charge and push the round into full battery.
Then the next week read something like your post, and I feel better.
I'll drop the round on the sled and nudge it forward just a little then blam, drop the bolt.
Then the next week - - - :)
 
#15 ·
Maybe I'm ignorant because I don't have any of the big bore ARs, but I don't think brushing slam fires aside like any other malfunction is a good idea.

The rifle isn't supposed to fire when you drop the bolt. Ever. There is clearly something going wrong here.

If the firing pin were sticking out it would slam fire when it strips from the mag, too. Same with a headspace issue I think. Pin inertia sounds feasible, you would have to fix that with a lighter pin or lighter buffer spring. I would probably replace both just to be safe.
 
#16 ·
Maybe I'm ignorant because I don't have any of the big bore ARs, but I don't think brushing slam fires aside like any other malfunction is a good idea.

The rifle isn't supposed to fire when you drop the bolt. Ever. There is clearly something going wrong here.

If the firing pin were sticking out it would slam fire when it strips from the mag, too. Same with a headspace issue I think. Pin inertia sounds feasible, you would have to fix that with a lighter pin or lighter buffer spring. I would probably replace both just to be safe.
There is nothing wrong with the rifle.

458 SOCOM wasn't alive at the time Eugene Stoner designed the operating system

Over the years there have been countless "improvements / enhancements" which take the core design to its limits

The slamfire ISNT considered just another malfunction , in re-reading this post I don't see anybody making that claim....

To say the rifle has a issue is just inciting panic, many have already taken a kick at the dead horse in this one : a slamfire occurred because the drag/friction from the magazine was skipped (i.e. Stoner's design subverted) therefore an unexpected discharge occurred when the full weight of the carrier slug the free floating firing pin forward and set off the thin cupped primer.

I'd bet good money the slamfire wouldn't occur once in a 1000 rounds of normal firing conditions as the 458 SOCOM was designed and developed to ensure proper ordinary function.
 
#17 ·
I would argue that dropping the bolt on a round that's been single loaded without a mag should be considered normal conditions.

If it was happening on a 223 vs a 458 would there still be the same discussion? That's a legit question. I'm not trying to start a fight here.

Personally, I wouldn't accept that something like that is just going to happen sometimes, but to each their own. Obviously all the normal gun safety rules apply, but unexpected gunshots arent good.
 
#18 ·
My slam fire was not a .458 . If you remove your bcg and push the pin forward you will see it doesn't protrude out of the bolt until the bolt has partially turned engaging the barrel ext lugs , that is not only a good thing as it helps alleviate open battery dischages but also slows the carrier down and the firing pin forward inertia is particularly stopped before it can hit the primer . For the slam fire to happen as described first the carrier is released and allowed to slam forward freely without being slowed down by the stripping of a new cartridge from the magazine and quite possibly a worn in well lubed carrier at that . Then the bolt and lugs would have to match up smoothly so as Not to slow down the rotation of the bolt . Of course spring strength and buffer weight may play a part .A firing pin at the top of weigh or length specifications would play a part . A weak extractor spring would slow the bolt down less than a strong one . A cartridge with tight headspace and last but not least a thin primer . How many of these components would have to be part of the equation I don't know . I don't believe it would be possible unless at least 2 for sure, one being carrier being allowed to slam forward with out the inertia being dampened by stripping a round and primers with thin skin or at least thinner than mil spec , if that is the proper word . I'm pretty sure one or more of the other factors may have to be present also but I don't believe any combination of the others would cause a problem if Carrier was stripping a round from mag .as it is designed to do .

Sent from my Moto E (4) using Tapatalk
 
#19 · (Edited)
I don't know how dropping the bolt on a chambered round without a magazine in place can be argued as a normal condition. There is nothing in the design that suggests that this will be a normal condition.

None the less, this thread was about a .458 Socom which is well outside the original design of the rifle anyway. As pointed out a couple of times above, this round uses a large rifle ( oops, Pistol as pointed out below) primer which is not hardened. Normally, a regular AR was designed to be used with a hardened small rifle primer which is commonly thought as insurance against a slam fire. Yes, many a round has probably been loaded with a standard small primer and we know that some are more soft that others (there have been lists of primers which seem to work), and we don't see many reported slam fires. BUT, it seems that in this case that the OP may be suffering a slam fire. Unfortunately he has not been back to confirm the condition is as we suspect.
 
#22 ·
There are several threads on the .458Socom board regarding this problem.

Big Bore has written several good posts on the subject.

He mentions Never dropping the bolt on a loaded chamber and discusses the soft primers.

He also notes the possibility of a "dropped" hammer and suggests dropping the bolt Carrier several times on an EMPTY chamber and then pulling the trigger to make sure the hammer remained cocked and did not drop until the trigger was pulled.

Further, he suggests measuring to be sure the firing pin does not protrude more than 0.032" and buffing it down it is longer than that.

If the OP is not a member of the .458 board, it would be worth joining.
 
#26 ·
There are several threads on the .458Socom board regarding this problem.

Big Bore has written several good posts on the subject.

He mentions Never dropping the bolt on a loaded chamber and discusses the soft primers.

He also notes the possibility of a "dropped" hammer and suggests dropping the bolt Carrier several times on an EMPTY chamber and then pulling the trigger to make sure the hammer remained cocked and did not drop until the trigger was pulled.

Further, he suggests measuring to be sure the firing pin does not protrude more than 0.032" and buffing it down it is longer than that.

If the OP is not a member of the .458 board, it would be worth joining.
I went to the 458 forum and new registrations are disabled.
 
#23 ·
I say you are absolutely right Mine was a 6.8 with old Remington loads ,not sure the size primer . Only shot them that one time but as you stated I was not using firearm the way it was designed to be used and even though I have no idea what exact primer it was I'm pretty sure it wasn't hard as the ones it is designed for . Any change from original design or deviation from normal procedure can and sometimes does have consequences .

Sent from my Moto E (4) using Tapatalk
 
#25 ·
Thanks to all of you for your insight. The 458 is a new to me pistol build. Shot very little and all new parts. I normally do single load a round in the chamber, release the carrier and then insert the mag when I am hunting. I have never had a slam fire with my 5.56 or 6.8 rifles or pistols doing this in over 30 years. This 458 did this twice. I also noticed that when I single loaded a round and slowly let the carrier forward and tapped the forward assist that there was a larger than normal dimple in the primer when I extracted that live round. I wasn't aware the 458 Socom used pistol primers as I just traded for the gun and ordered dies for it, so I haven't had a chance to look up loading data. Once again I thank you all for sharing your knowledge and experiences with me.
 
#33 ·
If I understand your post here, it looks like you still had firing pin to primer contact even when easing the bolt forward and using the forward assist. That sounds like you had some sort of firing pin protrusion going on with the old pin.
 
#30 ·
458 slam fire

Unless I am misunderstanding something, you should NEVER single load a cartridge in the chamber of any AR15 style rifle and then allow the bolt to slam shut on it. The firing pin is free floating and not controlled by a spring. When you let the bolt slam shut on a cartridge singularly loaded into the chamber the firing pin is free to slam forward at high speed. When you let the bolt fly forward and strip a round from the chamber the act of stripping the round slows down the forward movement of the bolt enough to keep the firing pin from slamming into the primer with enough force to discharge the round. Even when stripping a round from the magazine, the firing pin will hit the primer hard enough to put a small dimple in it. I don't think there is anything wrong with the rifle (unless the hammer happens to be falling when you do this) it just isn't how an AR15 is designed to be operated.
 
#32 ·
Update. A TI firing pin did the trick. I tested it with two different kinds of ammo.
I won't be single loading and hitting the bolt release anymore either.
Glad to hear the Ti firing pin helped you, I figured it helped on the 375 socom so why wouldn't it on the 458 socom, after all they use the same basic brass and the same primers.
 
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