If you look at the picture in post #32, you will see the carrier cam slot has a 'straight' section towards the rear, it is in the area the the bolt if fully turned (and locked) and where the pin will start being able to engage the primer. Up until this point, the pin cannot exceed past the bolt face.
Robinson Arms XCR. 223 - Bolt carrier blew up **UPDATE**
- Thread starter cyclic
- Start date
Hi Cyclic,
There has been lot of dicussion on various forums regarding the XCR firing pins, chamfering on the bolt head and craters in the primers. In fact mild cratering of primers is generally an accepted "mark" of an XCR. Similarly the fluting of case mouths is common to HK rifles. Rifles leave their various marks on spent cases.
I have never encounterd another case of an XCR being suspected of firing out of battery. This is a rare event in any rifle given the millions of rounds fired.
If you have examined all the pieces and can not determine a cause, it will just have to remain unexplained.... It is no reason to be discouraged with your rifle. I consider the XCR to be a well designed rifle.
Cheers,
B
There has been lot of dicussion on various forums regarding the XCR firing pins, chamfering on the bolt head and craters in the primers. In fact mild cratering of primers is generally an accepted "mark" of an XCR. Similarly the fluting of case mouths is common to HK rifles. Rifles leave their various marks on spent cases.
I have never encounterd another case of an XCR being suspected of firing out of battery. This is a rare event in any rifle given the millions of rounds fired.
If you have examined all the pieces and can not determine a cause, it will just have to remain unexplained.... It is no reason to be discouraged with your rifle. I consider the XCR to be a well designed rifle.
Cheers,
B
The reason for the fluting of the chambers in HK rifles has nothing to do with distinguishing cartridge marks it is a reliability feature for ease of extraction on fired casing as as well on the G series and MP platforms had a fluted chamber it was needed for the delayed roller locking system to operate .
One of Two things happened with the rifle :
1 it fired while in battery and in which case you mis loaded the type of powder you used into the powder measure in which case there is most likely there is damage to the barrel ?
#2 It fired out of battery in which the possibility of barrel damage is negligible
One of Two things happened with the rifle :
1 it fired while in battery and in which case you mis loaded the type of powder you used into the powder measure in which case there is most likely there is damage to the barrel ?
#2 It fired out of battery in which the possibility of barrel damage is negligible
- Location
- Georgetown Ontario
I think you missunderstood what he was saying. He didn't mean the marks are there for identification, only that some firearms leave very specific marks on fired cases. I'd be worried if my Colt left cratered primers like my XCR does LOL.
You picked up a piece of discarded range brass and have no idea how many times it was fired. Cases fired too many times stretch and create a weak spot just ahead of the case head web.
It is possible that Brobees wrinkled neck theory jammed the bullet in the neck and led to an over pressure. But an old case can separate from normal pressures.
What I see most in this thread is a whole bunch of guys who haven't got a clue how these rifles work. Other than a stuck firing pin it is nearly impossible to have an out of battery detonation. Additionally an out of battery explosion would be nearly catastrophic. The OP described this as a slightly louder bang and some unusual smoke. That is not possible with an unlocked breech.
The crap around the breech and chamber doesn't look at all like tumbling media. Go have a look in your tumbler. Is the media super fine like that or is it very coarse? It is not uncommon to have unhurt powder granules blown out with a separated case.
I'm going home to hug my XCR...
I'm suitably impressed how well it held up.
This is, I think, the first time I've seen pictures of an XCR that's had this big of a failure.
Maybe forward them on to RA and see what they have to say?
I'm suitably impressed how well it held up.
This is, I think, the first time I've seen pictures of an XCR that's had this big of a failure.
Maybe forward them on to RA and see what they have to say?
blaxsun
CGN Ultra frequent flyer
Compared to...?
That's what I'm gleaming from all of this. Someone suggested a case-head separation, so is that the expert consensus at this point based on available information?
It is possible to split or separate a case while the bolt is firmly locked.
If it had been an out of battery event he'd have known it and had lots of time to contemplate that while lying in hospital having the bolt and sundry bits of metal removed from his face.
The case was on it's second load, I do know how many times it was loaded (swaged it so know first time I removed primer crimp)and that was one to many for that particular case.
I appreciate everyones input will update with parts quote. Case failure seems to be the most likely conclusion I can draw after looking at what is in front of me and remembering what took place.
I appreciate everyones input will update with parts quote. Case failure seems to be the most likely conclusion I can draw after looking at what is in front of me and remembering what took place.
I've spent a lot of time thinking about this. What if we are making some large assumptions regarding the bolt carrier itself. How would a case head separation cause the bolt carrier to blow into pieces? This does not seem logical to me. What if a faulty carrier is the CAUSE of the problem and not the result?
Good point, the only thing that makes me convinced is why did the extractor get stripped off and the magazine get blown out the bottom of the mag well.
Just had a guy over to look at it who knows all about ammunition malfunctions (30 + yrs), he thinks the case failed on extraction also (Malice's original theory). We had initial launch of projectile, then after that we had the problem. When that gas escaped the head area, it blew back the bolt and opened up the carrier like a banana, that's why bolt and broeken carrier got jammed in the half open position, i think as the extractor & bolt grabbed that case it peeled that cheap sucker open. That's why I had so little damage, a lot of the gas went out already, and that's why i had a funky boom, it went out barrel then out the back.
Good lesson learned for me with respect to brass, sucks I will be eating a few hundred dollar bill, but better than eating some of my receiver.
sikwhiskey
CGN Regular
- Location
- Lethbridge
I'm still not convinced it was faulty brass, the carrier did fail but was it the cause? with the bolt locked in the barrel lug, the op rod would be the only thing forcing the carrier to move rear wards? Would a fail on the carrier as the op rod was moving rear wards under pressure cause this? I think it could, but to this extent?
I have measured my bolt and carrier, locked in the barrel, with the lower separated, the hammer can hit the firing pin with 0.02 " of access head space, though it would be a light strike against the firing pin.
Interesting, hope we can get some definitive answers!
So the consensus seems to be that it fired out of battery... so loctite is indeed back on the list of potential culprits then...
I am not an AR shooter, so don't now about the rifle itself. Tell me though, when you seat the bullet...did you adjust your die such that you just touch the top of the casing and back out a 1/2 turn or so, and then adjust for seating depth? Or do you squeeze and crimp? Do you uniformly trim cases first? A crimped neck will still chamber up to the point in the chamber where the shoulder swaged down to the neck. I think the bottom (toe) of the shoulder became bulged from the loading process and jammed into the chamber. The firing pin smoked the primer pretty good, because one can actually see the little crater.
The reason I ask is that the casing blew out the back and front (to eject the bullet) and then the residual forces (spring?) and heat caused it to fold and collapse into the chamber. That happens when the chamber walls are absent to adequately restrain the rapidly expanding casing. Kinda like a balloon popping partially in a tube.
I do not think it was neck failure or case failure. I think it was a deformed shoulder (out of round - compressed by the die not being adjusted correctly). The shoulder, then too wide...jammed partway into the chamber and the firing pin released when the trigger was pulled. Out of battery.
Guys. It wasn't fired out of battery. Look at any picture of a gun fired out of battery and the receiver is toast. Even steel receivers. Even if you don't agree it was a case failure that caused the issue, it did not fire out of battery. It is virtually impossible for an AR or XCR to fire out of battery.
Look at the cam lug on the bolt. See the big notch taken out of it? What do you think caused that? From slamming into the carrier.
Look at the cam lug on the bolt. See the big notch taken out of it? What do you think caused that? From slamming into the carrier.
It is perfectly logical. The case fails and dumps 50,000 psi of gas into the bolt and carrier. Those parts are not designed to contain that kind of instant pressure spike.
The idea of a carrier failure is what makes no sense. The carrier is not involved in the firin sequence until the bullet has passed the gas port. By which time the gas pressure has dropped to around 5,000 - 8,000 psi. The delay in the unlocking process means that the bullet has left the barrel before the breech unlocks and pressures have dropped to nearly atmospheric.
So how could a carrier failure allow a massive pressure spike to blow the case when the bore pressure has already dropped to nearly zero by the time the bolt unlocks?
Instead of putting forth crank theories maybe try to understand how the system works first.
Not possible. The case is NEVER containing any pressure during the extraction cycle. Pressure within the barrel has dropped to virtually zero BEFORE the bolt unlocks. If that were not the case you would get a massive shot of high pressure gas in the face with every shot.
I would be highly sceptical of an "expert" who doesn't understand the basic functioning cycle of a gas operated rifle.
It is just a suspicion that the rifle indeed fired from while not in full battery but in partial battery I have seen this occur in other semi automatic rifles M305 and M1 Garand and do the same damage with out having a catastrophic failure and involving injuries . The bolt is not fully seated in the barrel .The action unlocks as the bullet is traveling down the barrel how much damage the rifle receives translates as to how far down the barrel the bullet has traveled .As the bullet moves down the barrel the pressure drops this means that if the action were partially locked it would not need much to come out of partial battery and release the pressure into the breech .This could occur at past peak pressure during the recoil pulse before the bullet passes the gas port. With a improperly or partially seated bolt the pressure of force is equal so that lets say 50,000 psi is the is the pressure of the fired cartridge at the moment of detonation it would be enough to keep the bolt from opening at peak pressure as the bullet moves down the pressure drops meaning that it is easier for the bolt to unlock with the remaining pressure in the barrel . The time cycle for this event is almost instantaneous .The period of time from when you press the trigger till the round is fired is longer than it takes for the bullet to leave the barrel !
Sorry Savage, still not possible with an XCR or AR15. The firing pin won't be able to reach the bolt face unless it's locked (as previously stated many times). The barrel doesn't/can't unlock due to pressure alone, only once the bullet passes the gas port and siphons gas back to hit the carrier. The carrier moving rearwards turns the bolt, unlocking it. If you removed the carrier and just used the bolt to lock the round in place, and hit the firing pin, the bolt would stay locked.
Don't know about the M1 or M305.
Don't know about the M1 or M305.
