Had a kaboom with my reloads.

[Bimmer]

Firing out of battery by means of dropping the hammer, not an optional explanation...

Is it possible that a stuck firing pin did this, in combination with not fully chambering?

The back of the case looks like it wasn't supported when the cartridge fired...

[Clint]

Is it possible that a stuck firing pin did this, in combination with not fully chambering?

The back of the case looks like it wasn't supported when the cartridge fired...

In the ARFOW, the firing pin is positively retracted when the bolt is unlocked.

The firing pin is only "unblocked" after the bolt has been rotated into the locked position.


That bell shape in the brass could be due to an out of spec chamber feed mouth / feed cone not supporting the brass well.

This is a likely culprit in a "cheap" AR barrel.

[Bimmer]

In the ARFOW, the firing pin is positively retracted when the bolt is unlocked...

Oh, yeah... I guess I was thinking M14.

That bell shape in the brass could be due to an out of spec chamber feed mouth / feed cone not supporting the brass well.

So radical over-pressure and an out-of-spec chamber?

[Ned Christiansen]

The cartridge was fully chambered. They always look like they were "sticking out" a bit but what we see here is the brass having flowed into the chamfer/radius at the chamber entry at the rear face of the barrel, and into the chamfer where the bolt face recess meets the bolt face.

[Bimmer]

They always look like they were "sticking out" a bit but what we see here is the brass having flowed into the chamfer/radius at the chamber entry at the rear face of the barrel, and into the chamfer where the bolt face recess meets the bolt face.

So this is just a case of waaay too much pressure?

[Ned Christiansen]

My opinion, yes. We just don't know why.... apologies to the OP but being handloads generally opens up a lot of possibilities. Not impugning your abilities as a reloader OP, things can happen under the best of conditions, and as we sometimes see, at the ammo factory too.

[scottcc]

My opinion, yes. We just don't know why.... apologies to the OP but being handloads generally opens up a lot of possibilities. Not impugning your abilities as a reloader OP, things can happen under the best of conditions, and as we sometimes see, at the ammo factory too.

Could it be from AR Comp temp sensitive? As I stated it was in June and on a hot day at that. The ammo was in the trunk of the car. I was using metal 20 round mags, they were warm, then setting in the sun made them heat up more, while I was setting things up.

For what it's worth I do trim cases, check OAL and also shake to hear powder.

Sent from my cp3705AS using Tapatalk

[MagpulBuff]

Good that it didn't all go south!

[markm]

Out of battery is nearly impossible. Even if debris ignited the primer, the force of the bolt closing would be needed to create the impact needed.

A bad case is unlikely or it would have probably failed on the original firing of the factory load, but again... maybe.

Most likely is an over charge. I don't know much about AR comp, but a ball powder with only 23 gr leaves A LOT of case volume available for an over charge.

And as far a reloads, Good ones run rings around factory ammo, and are much more trustworthy and predictable. I wouldn't run factory through a suppressor or a machine gun.

[Blanksguy]

scottcc,
First......do you use mixed manufacturer brass (?)……...and do you process all of this at the same time or separate into "lots" to be processed/loaded as "lots" (?).
Do you trim for case OAL after resizing or before (?).
During your re-loading phase...…...do you check "neck-tension" of the bullet being held by the case (after seating) (?).
Do you use bullets with or without "cannelure" (?)…...and do you use a form of tapper-crimp or "factory-crimp" on the projectiles (?).

After looking at your case photos...….what I am seeing (due to the flow of the brass) is "over-pressure" due most likely to bullet "set-back" during chambering. This bullet set-back would make your chamber-pressure increase dramatically.

Some possible causes:
1: Sizing after trimming cases for length. This gives you different length cases "and" will effect neck tension.
2: Use of cartridge-cases with different OAL.....again, effects neck-tension.
3: Using a case with a "split-neck" missed during case-inspection....again, loss of neck-tension.
4: Use of mixed weight bullets during loading of the same powder-charge.
5: .......….or this could be as simple as your cartridge didn't chamber at first try (bullet hitting breach-face and set-back into case)......you pull the charging-handle back slightly where the cartridge is allowed to chamber without being inspected...…….and then fired/"BOOOOOM".

What also helps some re-loaders stop bullet set-back is the use of bullets with a cannelure to allow the use of a factory-crimping-die.
…..or finding a way to insure that each bullet is seated/crimped at the case-mouth of the cartridge so that it can't move during chambering.

Regards, RichardS
US Army, RET