Robinson Arms XCR. 223 - Bolt carrier blew up **UPDATE**

cancer said:
To me, it looks like pieces of brass in the chamber. Did you take these pieces out and examine them? Shouldn't be hard to tell brass from what should be burned up pieces of corn cob or walnut. That is, unless you're tumbling in brass media, which would be new.

Also, from the look of the cartridge, there was no way that thing was fired in battery. When you fire in battery you don't see cartridges all twisted up like that. Over pressured cartridges will blow off the back end of the cartridge and leave the side walls, and throat of the cartridge stuck in the barrel. All the brass you get to see is the very bottom, and more often than not it'll be either long gone or stuck in the extractor (or what's left of it), the rest of the case stays in the barrel.

Also, look at the primer. That thing appears as round as it was when it was new. If this was an over pressure problem, the primer would typically be flat (there are rare exceptions).

Frankly, this shows some pretty glaring signs of an out of battery firing.

Do you full length resize your brass? Also was this brass fired in your gun prior to reloading, or is it 'from parts unknown'? Lastly, did you get the ka-boom after you pulled the trigger, or after the action cycled? I'm not familiar with the XCR, will the firing pin more forward when the action is open?
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A big plus 1 to all this. There is no way the bolt was closed then that round went off.

Cheers,

Brobee
 
MALICE i think your last assessment nailed it on the head. After looking at everything that is what happened, never going to use that brass again.

Think it is the cheap black box FC headstamped stuff that litters ranges. I usually only use IVI or Lake City brass, but had a few of these that i had picked up and loaded 50 or so with them.
 
As to what can cause an out of battery firing: one common progressive press reloading error I see often (having personally experience ld it as well as witnessing friends ammo having the same issue) is a bunged up case mouth which happens when seating the bullet. A small bit of the case mouth will wind up folded backwards and kinked, forming a big burr at the transition between the case mouth and the bullet.

The result is a round that almost completely chambers, but sits 0.025 to 0.050 back from where it should be. On most semi autos, it will keep the bolt from completely rotating into battery. To protect from out of battery firing, most semi autos also have design safety features built into the gun to theoretically prevent the hammer from being able to strike the pin, or the pin to move forward when hit, however it is my experience that they do not always work as intended. I've seen this specific problem enough that I now personally inspect every round that comes out of my 650, as well as every round I load into a semi's magazine.

Cheers,

Brobee
 
Brobee said:
As to what can cause an out of battery firing: one common progressive press reloading error I see often (having personally experience ld it as well as witnessing friends ammo having the same issue) is a bunged up case mouth which happens when seating the bullet. A small bit of the case mouth will wind up folded backwards and kinked, forming a big burr at the transition between the case mouth and the bullet.

The result is a round that almost completely chambers, but sits 0.025 to 0.050 back from where it should be. On most semi autos, it will keep the bolt from completely rotating into battery. To protect from out of battery firing, most semi autos also have design safety features built into the gun to theoretically prevent the hammer from being able to strike the pin, or the pin to move forward when hit, however it is my experience that they do not always work as intended. I've seen this specific problem enough that I now personally inspect every round that comes out of my 650, as well as every round I load into a semi's magazine.

Cheers,

Brobee
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Brobee,

I use a 650 also, I do inspect every round, chamber check it also. I will be paying closer attention to them from here on out and being a lot pickier with the brass I am using.
 
cyclic said:
barrel.jpg
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looks like partially consumed powder rather than "media" of some type.

Usually seen when cleaning low pressure revolvers, and when I've had case head separations in .303Brit...

When you overpressure a cartridge the usual result in a locked breech fiearm is difficult extraction, rather than case failure. That would tend to be the result of cleaning media left in the case.

I believe you had an out of battery firing, ie) the case was chambered just enough to overcome the hammer stop on the bolt carrier, then the case head failed.

1st question; was this the first round from that magazine? did you ease the chamber closed? What you experienced is a(the) text book reason for not doing so.

perhaps there was debris from a previous round left in the chamber-

You were firing handloads so:

perhaps the neck was crooked and stopped the case from fully chambering-

the case mouth was oversize

the case was oversize at the base or shoulder-

the case was overlength-

the primer was projecting from the head enough to stop the chamber from fully closing-


Then when the failure occurred the gun functioned properly in protecting the operator from injury...
 
Lee Enfiled,

It was the 3 rd shot out of the magazine, these loads were all checked with a case guage.

The FC cases are short, I also measure and trim all cases, that case was probably 1.145, a tad short.
 
To bypass the hammer stop on the carrier, the bolt has to be locked in the barrel extension. It cannot be halfway locked, it needs to fully turn and lock in the barrel before the carrier even starts to move forward to expose the top of the firing pin.

You'r all saying a fully locked in place bolt in the barrel extension led to a out of batterie hammer strike???? I'm not sure, maybe you guys are suggesting the hammer defied physics and went through the 1/4 inch thick piece of metal blocking it until it's in batterie? Or that the barrel extension is out of spec?...by half and inch? could be I guess...
 
I believe it was a faulty case that led to this, i just went through my entire reload stash and pulled 70 of those cheap federal cases i picked up off ground, time to pull some bullets.

There is good federal brass out there, marked FC and year, but federal civilian marked FC then .223 REM is what blew up here, and apparently not good for reloading.
 
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For whatever reason that round fired before being fully chambered.

The give-away is the portion of the case body just above the head where it was blown out to look like the inside of an old tire. A bulge like that is impossible to form if the case is supported in the chamber.
 
Boo- I have to disagree. When the bolt unlocks, there is still pressure in the barrel (although nowhere near as much as when the round originally lights). This is what (after the bolt unlocks) causes the bolt to move rearward and extract the case. The area that's bulged is the area of the case that stretches each time its fired and the more you use the case, the thinner it gets until you either dispose of it or it fails. Aside from a broken firing pin, there is no way (as mentioned above) that the firing pin can contact the case until it is locked. Since there is no damage to the edges of the locking lugs, it's evident it was not just slightly locked. The bulge is more likely caused since one the case failed, rather than the entire case (which would normally be sealed the length of the chamber) pushing the bolt backwards, the gas did that job and then the case was left fully unsupported causing it to bulge and blow out. I would imagine some of the damage on the case is also caused by it being pried out after the fact,
 
cyclic said:
Lee Enfiled,

It was the 3 rd shot out of the magazine, these loads were all checked with a case guage.

The FC cases are short, I also measure and trim all cases, that case was probably 1.145, a tad short.
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Just to confirm, by case gauge, you mean a headspacing gauge like a WIlson or Dillon?

For what it's worth, I stopped using Federal because I found some cases when resized would fall to the bottom of the guage.
 
To add to the firing pin aspect, the firing pin protrusion is only about .035-.050" (my .50bmg is .080"). By the time the carrier is forward enough to allow the firing pin to be flush with the bolt face the lugs are already almost fully rotated in the barrel extension which is more than enough to support the lugs.

Added: I think the damage to the upper receiver would have been catastrophic had it fired out of battery. Since the upper is still intact, I believe it's because the bullet had already traveled past the gas port, unlocking the bolt, and the pressure was reduced.
 
*MALICE* said:
To add to the firing pin aspect, the firing pin protrusion is only about .035-.050" (my .50bmg is .080"). By the time the carrier is forward enough to allow the firing pin to be flush with the bolt face the lugs are already almost fully rotated in the barrel extension which is more than enough to support the lugs.
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But consider the senario where the firing fin was "stuck" in the forward position due to debris or other fouling. The .035 to .050 protrusion would likely light up the cartrige before the locking lugs were fully engaged. This would be an "out of battery" dicharge and possibly cause the damage.

The firing pin should be removed from the bolt and thoroughly inspected. The bolt should also be inspected for debris in the firing pin channel.

Cheers,

B
 
Bojangles said:
But consider the senario where the firing fin was "stuck" in the forward position due to debris or other fouling. The .035 to .050 protrusion would likely light up the cartrige before the locking lugs were fully engaged. This would be an "out of battery" dicharge and possibly cause the damage.

The firing pin should be removed from the bolt and thoroughly inspected. The bolt should also be inspected for debris in the firing pin channel.

Cheers,

B
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Did that, it's all good, firing pin has no issues.
 
But consider the senario where the firing fin was "stuck" in the forward position due to debris or other fouling. The .035 to .050 protrusion would likely light up the cartrige before the locking lugs were fully engaged. This would be an "out of battery" dicharge and possibly cause the damage.

The firing pin should be removed from the bolt and thoroughly inspected. The bolt should also be inspected for debris in the firing pin channel.
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The way the bolt operates, if the pin was struck before fully seating, it would not be at the bolt face yet, and even if the hammer was riding the pin, by the time it made it flush with the bolt face, the bolt would be rotated into a locked position. If you have a XCR or AR handy, extend the bolt from the carrier, push on the hammer end of the firing pin, start 'closing' the bolt and see when the pin starts to protrude from the face. By the time it becomes flush, the bolt has finished rotating and is now moving straight back, so it will already be locked.

I cannot speak for other rotating bolt designs, but on an XCR or AR it's virtually impossible for the firing pin to hit the primer out of battery.
 
*MALICE* said:
Added: I think the damage to the upper receiver would have been catastrophic had it fired out of battery. Since the upper is still intact, I believe it's because the bullet had already traveled past the gas port, unlocking the bolt, and the pressure was reduced.
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I'm certainly not an expert (and don't reload), but if you do a Google image search for "ar15 fired out of battery" it returns examples with some pretty impressive damage (including one very serious injury from a fool who used a mallet to try and ram-home an incorrectly-sized .50BMG). While bad, this doesn't seem to be quite as destructive.
 
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