DON'T let the bolt slam home on an already chambered round

TACTICAL111 said:
Please provide more information. How many bolts have you seen fail ? When, where? What were the causes of the failures?
Thanks
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This makes a minimum of three in the last few months, all have the right lug separating catastrophically. Causes, still being determined and nobody knows for sure as these aren't aviation crashes, nobody investigates them, most would go unreported here as well as many owners aren't CGN'ers. You're reading about one right now, then one I have at home still trying to figure out, and one more for sure quite recently was a dealer who reported it in watermine's thread about the same blow up. He had one fail when they were firing it the exact same way, right lug blew off. Given the bolt set back seen in Norcs fairly often, this is seeming more and more likely, weak bolts. Looking forward to having the one I have tested.

CanuckR, if you're interested I'd send yours in for the test with the one I have and see if there's a common thread, would certainly help a lot of folks to know if there's a bolt problem.
 
Hi newby questions here, but I thought 'out of battery' meant no, or next to no lug engagement. Hard to tell from the pics on my phone but the lugs on this rifle were what 50-70% engaged? I would hope that if the bolt was good quality and both lugs were bearing on the receiver properly that this kind of failure should not occur. Kinda makes me a bit scared of my chi com 14
 
sAdam said:
Hi newby questions here, but I thought 'out of battery' meant no, or next to no lug engagement. Hard to tell from the pics on my phone but the lugs on this rifle were what 50-70% engaged? I would hope that if the bolt was good quality and both lugs were bearing on the receiver properly that this kind of failure should not occur. Kinda makes me a bit scared of my chi com 14
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This has been documented to happen even with US military M1's and M14's etc. That's why it says exactly not to do it right in the official US Gov PAM's for the US made military spec weapons.

They put it in the manuals because they obviously experienced the exact same thing during extensive trials and testing prior to adopting the rifles for official use.

The cartridge didn't initiate out of battery and the bolt didn't break because the rifle was made in China........

It wouldn't have happened at all if he hadn't released the bolt fully from the rear onto an already chambered cartridge exactly as the OP stated.
 
What he's asking, is if the gun would blow up if it were a US bolt. No way to say, but if the lugs were mostly engaged, as would make sense for firing pin contact given they can only protrude max .06", one would hope it would hold. If all is as the owner figures, this one sure didn't, and there's more with the exact same failure very recently. The bolts have never been regarded as a high point of the Chinese M14, receivers and barrels decent, bolts are the most mentioned problem spot on the old old ones and concerned that's recurring now. They are at the bottom of the parts pile.
 
Lots of good points mentioned here and I will agree with Ardent up to a point.

We all know slam fires and out of battery can occur with these rifles inherent in their design no matter who makes them. We all know, or should know these concerns and how to minimize risk or prevent altogether.

As Ardent mentioned,.. the safety bridge is your friend in preventing out of battery kabooms for whatever reason it happens and they are many. In this particular rifle kaboom, a slam fire coupled with an out of battery bolt,.. probably destroyed the bolt.

Remember during an out of battery firing, the left lug being much smaller , may not have engagement at all or very little. This leaves the right lug, partially engaged, receiving 60,000 psi thrust against just the lower part of the right lug, causing a tripping effect on the structure and a resultant shearing.

This particular rifle with the combination of problems that all lined up this day, probably would not have survived with a USGI, LRB, Springfield or a MasterCraft Bolt.

Eliminate what caused the slam- fire.

Ensure your bridge will work for you, and install a new bolt. Personally if it happened to me, I'd minimize the chances of it in the future, and take this opportunity to install a Q.C 'ed proven quality bolt. This kaboom is not as simple as merely a too soft bolt.:canadaFlag:
 
Ardent said:
What he's asking, is if the gun would blow up if it were a US bolt. No way to say, but if the lugs were mostly engaged, as would make sense for firing pin contact given they can only protrude max .06", one would hope it would hold. If all is as the owner figures, this one sure didn't, and there's more with the exact same failure very recently. The bolts have never been regarded as a high point of the Chinese M14, receivers and barrels decent, bolts are the most mentioned problem spot on the old old ones and concerned that's recurring now. They are at the bottom of the parts pile.
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correct. and also the issue raised about the 'safety bridge' which I assume is the lip of material on the back of the bolt in conjunction with the little 90 degree 'L' extension on the firing pin that is supposed to keep the firing pin from going forward until in battery (or I guess in battery enough to prevent catastrophic failure).
I assume that the safety bridge (if I am talking about the right thing) is designed to prevent firing from a mis-timed hammer strike. if it is able to do this, it should certainly be able to prevent a slamfire from firing pin inertia alone.
 
Remember the OP let her fly shut on a chamber round. The velocity of the bolt going from 100mph forward to near zero forward momentum as it turns into battery, has imparted the same speed on the firing pin, but its free floating and now driving forward at 100mph on its way to the primer. The safety bridge which should prevent complete forward momentum of the pin till the bolt is at least 60%ish?? engaged in a normal cycle with a "round strip from the mag speed",.. is now rendered all but useless by the much faster speed of the bolt.

Lets rewind back here and see the combination of events that caused this.


Handloads. Possible oversize case if neck sized only as recommended by some to preserve brass life,..but leaving a very full chamber to start with so lots of ability to "push back" when the old firing pin comes steaming through. Factory loads may have prevented this, not sure??

Primers. Commercial primers that are thin and soft or both. Not recommended for this rifle, we all know it but use them anyhow. May have prevented this if Mil-spec

Slamming home on a chambered round. We all know the consequences, and you have the photos to prove it. Proper use of know issues would have prevented this.

Out of spec receiver safety bridge or too soft bolt? You will need expertise to correctly measure the bridge against the drawings, and your bolt can be PMI'ed at your local metallurgist lab for surface, core and if its made outr of fudge like 305Chevy cams in the 70s or Honda V/30 V65 motorcycles in the '80s.

Lots of things done wrong here, anyone one of these may not have kaboomed. Line them all up and the sum of their effect is in the photos.
 
sAdam said:
. I assume that the safety bridge (if I am talking about the right thing) is designed to prevent firing from a mis-timed hammer strike. if it is able to do this, it should certainly be able to prevent a slamfire from firing pin inertia alone.
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images

images


The receiver bridge with its camming surface and cutout work together with the tang of
the firing pin to: 1) mechanically retract the fi
ring pin when the bolt rotates to unlock after
firing, preventing a "sticky", rusted or gummed-up
firing pin from remaining in the forward
position during the rest of the cycle of op
eration and 2) prevent the firing pin from
slamming forward when the round being loaded
stops in the chamber, preventing a "slam
fire" while the bolt is still unlocked. The fi
ring pin can travel forward through the bridge
cutout only after the bolt has fully closed an
d locked. Additionally, the hammer cocking
machining cut on the rear end of the bolt prevents the hammer from striking the firing pin
until the bolt lugs have rotated into locked position.
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-"M14 Rifle History
and Development"-Lee Emmerson
 
Sluggo_m14 said:
images

images




-"M14 Rifle History
and Development"-Lee Emmerson
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ahh. thank you. I was remembering things a bit wrong. was mixing up hammer cocking machining cut with safety bridge. been a while since I have had time to go shooting and fart about with the gun.
 
Whoa. I forgot my mags at home once and spent a solid hour doing this. Bought the rifle used, did zero research. Milsurp ammo, Norc rifle. I think I may have used up all my good luck. Thanks for the info, lesson learned.
 
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