Tight chamber leads to Kaboom!

[C4IGrant]

http://www.ar15.com/forums/topic.htm...=393112&page=1

Anyone want to bet that the DPMS had a tight chamber and there was a pressure spike??



C4

[MX5]

The half dozen DPMS bbls that I've run a finish reamer into were all marked '5.56', but there sure is a lot of metal coming out of them.

[jmart]

I'm not buying it Grant. That's an ammo problem, either bullet setback or something seriously amiss, with either the Hornady cartridge or a squib from the preceding Silver Bear.

A brand new cartridge case can contain a decent pressure spike, but when something goes kaboom, pressures are well beyond what you would see from NATO ammo fired in a SAAMI chamber.

[Robb Jensen]

Probably somehow fired slightly out of battery.

[jmart]

How can an AR fire OOB? I'm trying to picture how the firing pin can protrude far enough beyond the bolt face to strike the primer, but the bolt not rotating and seating behind the locking lugs.

[Robb Jensen]

How can an AR fire OOB? I'm trying to picture how the firing pin can protrude far enough beyond the bolt face to strike the primer, but the bolt not rotating and seating behind the locking lugs.

Broken firing pin or too much firing pin protrusion which is why there is a MINimum and a MAXimum on the firing pin protrusion gauge.

[Iraqgunz]

We had the same thing happen here just before I arrived in October 2007 with a Bushmaster M4gery. Unfortunately, no one documented the ammo or conditions. It blew the barrel extension apart and messed up both the lower and upper receiver. My guess is that there was possibly a squib round, although I would venture to say that it would have also caused a malfunction and it should have been noticed. Hard to say. Personally I would not have let anyone dick with it until I had taken photos and documented everything first.

Since he was firing different types of ammo and unless they can recover the casing (headstamp) Hornady could easily say that the damage isn't their fault (my opinion only). It could also be a combination of tight chamber, ammo, etc...Voodoo?

[C4IGrant]

I'm not buying it Grant. That's an ammo problem, either bullet setback or something seriously amiss, with either the Hornady cartridge or a squib from the preceding Silver Bear.

A brand new cartridge case can contain a decent pressure spike, but when something goes kaboom, pressures are well beyond what you would see from NATO ammo fired in a SAAMI chamber.

Happens all the time. As the rep at Hornady said, they shot the rest of the ammo and there was zero issues. .223 chambers with 5.56 Pressure equals bad things. We see it all the time.


C4

[jmart]

Happens all the time. As the rep at Hornady said, they shot the rest of the ammo and there was zero issues. .223 chambers with 5.56 Pressure equals bad things. We see it all the time.


C4

What happened here does not happen all the time. This was a minor kaboom. Minor kabooms happen for reasons other than just a tight chamber.

I'll grant you that primers can pop, caseheads after multiple reloadings can separate (although virgin brass shouldn't), etc., but you don't have minor explosions going on in those instances. There's something else at work here. (The 2nd thread BTW had some interesting happenings, same ammo, same lot).

It could have been a bad round (light charge weight) that resulted in SEE. The rest of the ammo could have been fine. It could have been a minor bore obstruction. It could have several things that led to "the perfect storm" as Robb mentioned, but a SAAMI chamber by itself doesn't cause a kaboom.

[RD62]

http://www.ar15.com/forums/topic.htm...=393112&page=1

Anyone want to bet that the DPMS had a tight chamber and there was a pressure spike??



C4

It couldn't possibly have been an out of spec chamber because it was a DPMS chamber and they have 5.56 Nato chambers, and supply parts to the .mil, and are just as good as the Colts and LMT's and Noveske's you sell, and are alot cheaper.

Seriously though, maybe he can pick up the tab for his friends Dr bills for his finger, with the money he saved buying the DPMS.

-RD62