LWRC KABOOM!

[Old Powderman]

The AR design has undergone a number of changes--and some of those changes included re-design of the firing pin to prevent slam fires which did happen on earlier configurations.

[M&P1554]

I think I read he said, mild crimp was done. But that was my guess as well, bullet setback.

I crimp all my rounds, as all my weapons are semi autos.

[kdsd731]

I can tell you want the issue is. Your kaboom was caused by bullet setback.
I noted that your upper had the feed ramp profile cut into it. Thus, I believe that this is a carbine.

The rifle is the LWRC M6IC-SPR.
Assuming you are correct, what would cause the "belt" to have shown up? Would it do that forming if the bolt was completely shut?

[Wrangler John]

At this point everything is speculation, there is no way to know what single factor, or ensemble of factors, caused the failure. While my first guess was that salvaged range brass, one with incipient head separation from previous firings was the culprit, there is one other possible cause not yet discussed.

When loading with a progressive press, a short stroke or malfunctioning powder measure or case activated powder drop, can deliver a LIGHT load; one that is below the minimum. A light load can cause a pressure excursion, raising pressures beyond design limits. Only the cartridge subject to short stroking will evidence overpressure, while the rest will fire normally.

I had this happen when I opened a new canister of powder. A small piece of the Styrofoam security seal fell into the powder canister and, unseen, into the powder, then into the powder measure. I tried to set the measure by weighing each charge, but they were so erratic, varying by a grain or more, that I finally decided to check the measure. Disassembling the measure revealed the piece of Styrofoam stuck in the funnelling portion of the measure. It was acting as a flue dampener, holding back a portion of one charge and delivering it along with the next. Fortunately I was not using a progressive press, and even if I had been I always check several charges before loading.

I also use a mirror set up to view the inside of charged bottlenecked cases where a powder check die is not available, just for a precaution.

I have also experienced overpressure loads from charges that are too light. in one instance high pressures blew apart Varmint Grenade bullets inside the bore, with jacket fragments reaching 5.200 fps before wiping out an Oehler Skyscreen. Barnes confirmed that such failures were caused by excessive pressure. The rifle was unharmed, and the were no injuries. Always read and check everything constantly as you load, the brain often sees what it expects to find.

Also I had a similar experience by using a standard primer instead of a magnum primer. This resulted in a hangfire and double report (sort of a pop - BANG) do not mix primers or vary from a recipe.

[JagerDog]

Powder bridging in your drop tube could produce an over charge.

[Wrangler John]

LWRC does not sell a stripped lower to replace it. They well replace the barrel as standard procedure, replace the bcg and repair this receiver. A replacement complete upper on sale is $1650.

There are good quality uppers available for much less than $1650, for example check here:

http://www.fulton-armory.com/FAR-15-Complete-Uppers.aspx

Any body can build a new upper for considerably less that $1650, and have just the features they want. This is what I have done using these parts:

http://www.fulton-armory.com/AR-15-Upper-Parts.aspx

I like the side cocking upper receivers, as a preference but make it your way. Barrels? Sure:

http://www.fulton-armory.com/AR-15-Upper-Parts.aspx

And remember, this is just one vendor. The amount of stuff available is mind numbing.

[kdsd731]

There are good quality uppers available for much less than $1650, for example check here:

http://www.fulton-armory.com/FAR-15-Complete-Uppers.aspx

Any body can build a new upper for considerably less that $1650, and have just the features they want. This is what I have done using these parts:

http://www.fulton-armory.com/AR-15-Upper-Parts.aspx

I like the side cocking upper receivers, as a preference but make it your way. Barrels? Sure:

http://www.fulton-armory.com/AR-15-Upper-Parts.aspx

And remember, this is just one vendor. The amount of stuff available is mind numbing.

Yeah, but he doesn't want a mismatched LWRC rifle. He paid good money for a high quality rifle. That would just bug him. He will probably send it in to be welded through LWRC.

[fguffey]

This was not a squib failure. The barrel was unobstructed. It appears to have been way over pressured to me but how can he have over pressured it?

Reminds me of the 'One horse shay', nothing before and then suddenly, all at once and without warning it fell into a heap.

The case head shortened, the case head expanded/increased in diameter, the primer pocket increased in diameter, the flash hole increased in diameter. Etc., etc., the rifle was rendered to scrap suddenly and without warning, all at once. If this happened to me I would quit reloading. There is absolutely no reason for a shooter to load a round without knowing what is going to when the trigger is pulled.

I suggest reloading forums number the excuses.

F. Guffey

[Carsgunsandchics]

Another possibility. Light load round fires, projectile clears gas port but stops short of clearing the muzzle. Enough gas has passed to cycle the system. Case ejects next round loads. Firing the round instantly pressurizes the gas system as the end is plugged but the port is not. It immediately starts to unlock the bolt while still under full pressure. Carrier moves back and immediately the brass takes the hit swelling and blowing out with full pressure while being pulled from the chamber. Projectile strikes and blows out blocking projectile and clears the barrel.

Does this sound plausible?

[kdsd731]

If this happened to me I would quit reloading.
I suggest reloading forums number the excuses.

I guess he and I, since I was supervising, should just hang it up. Apparently if something ever were to go wrong, then clearly we're incompetent. Your advise was very helpful. Thank you.

Another possibility. Light load round fires, projectile clears gas port but stops short of clearing the muzzle. Enough gas has passed to cycle the system. Case ejects next round loads. Firing the round instantly pressurizes the gas system as the end is plugged but the port is not. It immediately starts to unlock the bolt while still under full pressure. Carrier moves back and immediately the brass takes the hit swelling and blowing out with full pressure while being pulled from the chamber. Projectile strikes and blows out blocking projectile and clears the barrel.
Does this sound plausible?

I don't know if that is possible without at least bulging the barrel? Is it? But in my case, I am 100% positive that there was no squib round prior to the malfunction. My friend has it on his go pro and you can clearly see the impact on the dirt prior to the malfunction. I appreciate the help in trying to figure it out though.

[fguffey]

There is absolutely no reason for a shooter to load a round without knowing what is going to when the trigger is pulled.

Yeah, but he doesn't want a mismatched LWRC rifle. He paid good money for a high quality rifle. That would just bug him. He will probably send it in to be welded through LWRC.

I guess he and I, since I was supervising, should just hang it up. Apparently if something ever were to go wrong, then clearly we're incompetent. Your advise was very helpful. Thank you.

"He paid good money for a good quality rifle" and then rendered it scrap. There is nothing I can change about that, there is a remote chance someone else with a quality rifle is reading this that does not understand the risk of chambering ammo and pulling the trigger. I am the fan of cutting/reducing the chances of this failure happening to someone else.

I am aware of failures, none of them have gone through the Internet. All of the failures I am aware of happened to someone I know. Everyone of the failure stories started with: "I screwed up etc..".

F. Guffey

[ar15barrels]

Please help me in understanding what the most likely cause of this failure is. My dad was rapid shooting his LWRC rifle with his own reloads. However, this was his first time reloading but I supervised him on his first and only 150 rounds on the press he's done. This was done on the Hornady ammo plant. The cases were mixed stamps and loaded with 55gr Xtreme's, Tula SR primers, 25gr of H335 and all were trimmed to 1.75" with the bullet set to 2.22" roughly mid cannelure. This was not a squib failure. The barrel was unobstructed. It appears to have been way over pressured to me but how can he have over pressured it? Also, I'm going to bring this upper to a gun smith for a thorough inspection. But, in your opinions, is this deformation and crack in critical enough areas to pose a safety concern? Obviously the correct was is a new upper. But, could it be safely reused in your opinion assuming the barrel is in 100% condition?

Read up on "powder bridging".
This happens with new powder measures from static and new reloaders who have not developed the proper rhythm with the press are more prone to it.

The bolt, receiver and the bolt carrier are toast.
The barrel MAY also be toast.
Check the extension for cracks.
Test headspace in the barrel with a new bolt and see if it passes.
The receiver can not be re-used.

[ar15barrels]

I'm kinda interested in the front half of the case.
It appears to be quite clean for not being completely chambered.
It almost looks like it could of been stuffed into the back of a torn case from a case head separation.

As mentioned in a previous post, look at the case head...it looks like a belted case now. It looks like out of battery ignition which resulted in case head separation. Then, the ejector ripped the already cracked case head during extraction.

what would cause the "belt" to have shown up?

I don't think you are understanding the pictures.
The case was COMPLETELY chambered.
The area that expanded to look like a belt is the unsupported part of the case which is strong enough to contain normal operating pressures without expanding.
What you are seeing is a case that was exposed to abnormally high pressures and expanded to the limits of the surrounding metal.

Would it do that forming if the bolt was completely shut?

Yes.

[ar15barrels]

I am leaning towards an out of battery detonation myself.

An AR firing pin can not hit the primer unless the bolt is FULLY locked in battery.
You can test this yourself by taking any AR, loading a cartridge in the chamber, then retracting the carrier 1/8" and putting a 1/8" allen wrench in between the barrel extension and the colt carrier and the firing it.
If the carrier is not FULLY closed, the firing pin bottoms out on the carrier without the firing pin protruding through the bolt face.

[ar15barrels]

Another possibility. Light load round fires, projectile clears gas port but stops short of clearing the muzzle. Enough gas has passed to cycle the system. Case ejects next round loads. Firing the round instantly pressurizes the gas system as the end is plugged but the port is not. It immediately starts to unlock the bolt while still under full pressure. Carrier moves back and immediately the brass takes the hit swelling and blowing out with full pressure while being pulled from the chamber. Projectile strikes and blows out blocking projectile and clears the barrel.

Does this sound plausible?

No.
Barrel blockages blow up or "ring" barrels.
These are very easy to detect.