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M4/1014 malfunction - locks up


SC-Texas

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Do you understand the relationship between the shell stop, release, and what activates each? I would suggest taking some spent shells and slowly cycle, dry fire, while observing how the firing mechanism activates/trips the feeding mech, and how the silver lever on the right side of the trigger guard simulates some of these actuations etc. Much long winded hypothesis can be scripted here, which would not educate you nearly so well as peering into the belly of your own beast while teasing it into revealing its secrets to you.

For example, Unobtanium asked about the round on the elevator. If none is delivered, the bolt has not been given the prepatory command to return to battery. This command occurs as the fresh round trips the lever that allows the bolt to carry on with business. Try it and see, slowwwwly cycling the bolt with empty shells, pulling trigger, ensuring the bolt is pulled FULLY to the rear, then try it simulating a weak marginal cycle, etc. With each variation, see how the internal mechanisms do/or do not respond. Try every conceivable variable and jot down what happens or does not, and compare those notes to your malfunctions.

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Do you understand the relationship between the shell stop, release, and what activates each? I would suggest taking some spent shells and slowly cycle, dry fire, while observing how the firing mechanism activates/trips the feeding mech, and how the silver lever on the right side of the trigger guard simulates some of these actuations etc. Much long winded hypothesis can be scripted here, which would not educate you nearly so well as peering into the belly of your own beast while teasing it into revealing its secrets to you.

For example, Unobtanium asked about the round on the elevator. If none is delivered, the bolt has not been given the prepatory command to return to battery. This command occurs as the fresh round trips the lever that allows the bolt to carry on with business. Try it and see, slowwwwly cycling the bolt with empty shells, pulling trigger, ensuring the bolt is pulled FULLY to the rear, then try it simulating a weak marginal cycle, etc. With each variation, see how the internal mechanisms do/or do not respond. Try every conceivable variable and jot down what happens or does not, and compare those notes to your malfunctions.

 

+1

 

PLEASE DESCRIBE IN DETAIL WHAT HAPPENS.

 

I will provide an example, that happened to me:

 

-Weapon: M4S90

-Variation from OEM: OEM Steel full-length magazine tube (can't get them anymore, don't ask), OEM spring/follower.

-Ammunition involved in failure: Winchester 12-pellet "magnum" 2.75" buckshot. 3" #4 Remington buckshot.

-Condition of weapon at time of failure: Firing/just fired next to last round in magazine. 1 round available in the weapon to be fired.

-Weapon condition at time of failure: Relatively clean, well-lubed.

-Situation: Fired slow-fire correctly from the shoulder.

-Failure: Bolt locked back, round either on follower or stuck in mag-tube. Follower is always "down" just like the gun had locked back on an empty chamber. There is one round remaining in the weapon.

 

 

Solution/Conclusion:

 

Magazine spring is not strong enough.

 

Rationale:

 

the shells move freely in the magazine tube. The less shells, the less spring pressure. When a healthy shell (2.75" 12-pellet buck or 3" #4 buck) is fired, the inertia of the weapon causes it to move backward. The shell, having mass and being at rest, does not wish to move (physics). It compresses the spring in the tube while the weapon around it moves backwards. The bolt cycles before the spring overcomes the resistance provided by the shell under heavy recoil. The above failure resulted.

 

Solution:

 

Back then, it was ordering a M1S90 Military spring. Now it is just buying one of Kip's Ti tubes which comes with a custom spring which I have found to perform flawlessly. Kip formerly sold these springs individually, I am not sure if this is still his practice, but he is a great guy to do business with, and if you are running a full-length magazine tube from anyone but Kip or FFT, and using the supplied spring, I would suspect that this might be the issue. (SOCOMguy also made/makes quality products, but I am unaware of what spring, if any, he offers with them).

 

 

______________________

 

The above might give you some insight into the issue. It is a thorough analysis of a similar problem I had back in 2008 or so.

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PS. I do not believe that a properly spec'ed M4 is capable of a non-user induced or maintenance-related malfunction using full-power ammunition, so I tracked you all over the internet and found that you are using a Nordic Components spring that you have trimmed, as well as a total mag-tube length to accommodate 9 shots, consisting of a +2 factory extension on your OEM 5-shot tube, and then a +2 extension on top of that.

 

This is likely the source of your problem.

 

Buying the spring from Kip SHOULD fix your issue, although it is designed for a 7-shot tube, Kip has opined in the past that it will work for a 9-shot tube.

 

It is certainly better than what you are currently running.

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Guest cleefurd

SC-Texas,

I have a few Wolff springs which were too long (by about 5 coils) which would not allow 7 rounds of the rare longish 2-3/4" ammo.

If Unobtanium's account rings true, and you elect to try one of our Wolff springs, we'll send you both (the current offering PLUS the older one with the 5 extra coils), the latter free of charge. If you get a chance let us know which one works best for your application. We are kicking around 8 and 9 round platforms, and would welcome your feedback.

_______________________________________________________________________

www.shop.carriercomp.com

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SC-Texas,

I have a few Wolff springs which were too long (by about 5 coils) which would not allow 7 rounds of the rare longish 2-3/4" ammo.

If Unobtanium's account rings true, and you elect to try one of our Wolff springs, we'll send you both (the current offering PLUS the older one with the 5 extra coils), the latter free of charge. If you get a chance let us know which one works best for your application. We are kicking around 8 and 9 round platforms, and would welcome your feedback.

_______________________________________________________________________

www.shop.carriercomp.com

 

Doesn't get any better than that!

This is where I sourced the above info on his setup:

http://www.brianenos.com/forums/index.php?showtopic=150964&view=findpost&p=1692132

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Guest cleefurd
Doesn't get any better than that!

This is where I sourced the above info on his setup:

http://www.brianenos.com/forums/index.php?showtopic=150964&view=findpost&p=1692132

 

That helps.

Looks like he is leaning towards the FFG? (likely he meant FFT) tubes. Their tube will work equally well with any spring he sources as a remedy. If he still needs an experimental spring after ordering them the offer still stands.

___________________________________________-

www.shop.carriercomp.com

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  • 2 weeks later...
PS. I do not believe that a properly spec'ed M4 is capable of a non-user induced or maintenance-related malfunction using full-power ammunition, so I tracked you all over the internet and found that you are using a Nordic Components spring that you have trimmed, as well as a total mag-tube length to accommodate 9 shots, consisting of a +2 factory extension on your OEM 5-shot tube, and then a +2 extension on top of that.

 

This is likely the source of your problem

 

It was doing this with the stock setup.

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It first did this at the ft Benning 3gun. It was stock in everyway.

 

It occasionally locked up over the intervening 2 years.

 

I added 922r parts.

 

I finally put the benelli tube on it without the constriction.

 

It still did locked up

 

The second gun was taken to Briley by the previous owner and they did some mods to, 922r etc.

I added the Nordic tubes Last month.

 

The lock ups occur in matches so I never really have time to diagnose the cause or take photos.

 

I have not been able to reproduce the lockup by hanfloading dummy shells during loading practice.

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It first did this at the ft Benning 3gun. It was stock in everyway.

 

It occasionally locked up over the intervening 2 years.

 

I added 922r parts.

 

I finally put the benelli tube on it without the constriction.

 

It still did locked up

 

The second gun was taken to Briley by the previous owner and they did some mods to, 922r etc.

I added the Nordic tubes Last month.

 

The lock ups occur in matches so I never really have time to diagnose the cause or take photos.

 

I have not been able to reproduce the lockup by hanfloading dummy shells during loading practice.

 

Did they ever occur using a different type of ammunition?

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