[Janq]

This morning over at CombatCarry there was a thread by someone about how he visually noticed his M&P .40 carry ammo had an unusual amount of setback.
That at first I paid not much mind to...but then over at SigForum I noticed another thread along the same lines only with folk providing detail about the reason why this occurs and how it can be very dangerous for operators.
I had not heard of this before and was unaware of this condition.
As such I figure I can't be the only one in the dark and am going to repost a reply from that thread for folks here...

"VERY important information regarding your auto loading pistols:

Catastrophic Failure of Semiautomatic Handguns

The following bulletin was received from the New Jersey State Police - Officer
Safety Division

Date: February 23, 2007

Continuous reloading an chambering of the same round may cause catastrophic
failure in semiautomatic handguns.

The Security Force at the Los Alamos National Laboratory in Los Alamos, New
Mexico, recently reported on the catastrophic failure of a semiautomatic
handgun when it was fired. The internal explosion caused the frame to break
while the slide and barrel separated from the weapon and traveled down range.
No one was injured in the incident. An investigation revealed that security
personnel were repeatedly charging the same round of ammunition into the
chamber.

Technical personnel at Glock Inc. advise that repeated chambering of the same
round may cause the bullet to move deeper in the casing, further compacting the
propellant. When a normal cartridge is fired, the firing pin hits the primer,
igniting the propellant. When the propellant burns, the gas pressure drives the
bullet out of the case and down the barrel. However, if the propellant has been
compact, the pressure may increase beyond the gun's maximum specifications,
causing the weapon to break apart.

Sigarms Inc's personnel confirm that reloading the same round five or six times
will cause the problems, noting that reloading the same round even once will
void their warranty.

Both manufacturers stress that the problem is not with the gun, but with
chambering the same round repeatedly. The NJ Regional Operations Intelligence
Center urges all law enforcement officers not to chamber the same round when
loading their weapons.

***For example, when you clean your weapon, most of us drop the magazine and
then pull the slide back thereby ejecting the round in the barrel.

After cleaning the weapon many of us will return the "same" round to the barrel
that we initially extracted. Each time the slide slams forward on that same
round it seats it deeper into the cartridge. Apparently, by seating the round
deeper into the cartridge, it creates greater pressure when the round is
intentionally detonated by a firing pin strike and is causing weapons to
explode.

The source for the above came from a posting at SigForum and IMHO the entire thread is a good read; http://sigforum.com/eve/forums/a/tpc/f/830601935/m/551100088

This is notable as for me as I do reuse/reload the same bullet in my carry ammo and do recharge my firearm often as per requirement of MA law.
When I remove my sidearm to enter a post office or some other persons home (my own policy as a courtesy) I will unload the weapon only to later recharge it with the smae round if not the one below it. Then when I get home I unload it again prior to storage only to recharge it once more the next time I go for it and likely using the same two bullets over and over.

Tonight I'm going to strip the top two bullets out of all my mags to check them for setback and/or discard them if they look sketchy. From ehre forward I'll as policy make sure to not reuse/recharge the same bullet more than say twice max.

IBDucmanalreadyknewthisstuff

Be safe out there,

- Janq

 

[DJ 9iron]

I've always popped a new round in when rechambering. Albeit for a different reason than you brought up Janq. I've noticed that the sides of the casing had minute scratches from either the mag or by simply sliding into the chamber. I always pop a new round and insert the previous deeper into the mag. Constant rotation.

 

[Janq]

Yep I've noticed those scratches on the case too but hadn't given it a second thought.
Maybe I should?

- Janq

 

[Ducman]

IBDucmanalreadyknewthisstuff

Be safe out there,

- Janq

IBRevolverFTW

 

[probably]

Thanks Janq!

 

[MrMcCrackin]

wow - going to inspect my carry weapons when i return to the so called safty of my home

 

[techwrtr2]

I've observed this with my 1911 and I've been making it a habit to rotate the round deeper into the mag and make sure it gets fired next time at the range.

 

[Gun-Nut]

Did not know this.
Thanks Janq.

 

[fatcat]

Did not know this... had the same ammo in the USP 40 for 4 years now... Guess I should change it out.

 

[Jeremy]

Ammo can be very picky, especially handgun ammo since it is stored primer up most of the time. With the cartridges held up and down the powder can pack from repeat handleing of the box which causes big variances in pressure and velocity, up to 30%. Which is why when your loading your supposed to rotate the cartridges end over end to loosen the powder so it lays along the whole case. Rifles aren't as particular mostly because most people store the long skiney shell boxes on there side.

 

[Janq]

Jeremy,

Would you suggest storing pistol ammo on it's point/box bottom side up or maybe rotating it on ocassion as such?

I've got over 2K rds. of right side up stored ammo that has been sitting for close to a year now and I never gave any thought to powder settling...which seems pretty sensible.

- Janq

 

[Jeremy]

The easiest thing IMO is to just shake the box when your going to load from it rather than re arrange all your ammo.

Find 1 of your oldest boxes and pull 1 shell straight up and out then hold it near your ear and slowly rotate it 180 so it's point up completely loose powder will sound smooth like sand sliding though the case, packed will sound uneven as the chunks fall.

 

[Ducman]

Here is another issue to beware of.

If you are shooting with low volume charge,

if the powder is against the bullet and none near the primer, the round may not light.

One of my shooting buddies was running into this issue when he was working on his lightning fast draw. The powder would not disperse before he pulled the trigger, this only happened on light steel load.

 

[MrMcCrackin]

i just checked my carry weapon loads

the sig was fine - no issues


the glock the top round has been pushed in not quite the thickness of a sheet of paper




so how far is too far? 1mm - 0.5mm?

 

[Ducman]

I have read that a 1/10" setback with cause pressure to double from 35K psi to 70K

here is a website

http://www.thegunzone.com/glock/kb-notes.html

 

[Jeremy]

I've never had problems with handgun ammo but i don't light load any either. I've had that problem with rifles tho and worse when it partially ligyhts and the bullet jams in the barrel from lack of velocity.

 

[MrMcCrackin]

I have read that a 1/10" setback with cause pressure to double from 35K psi to 70K

here is a website

http://www.thegunzone.com/glock/kb-notes.html

god damn 1/10" is almost a full 1/8" - thats HUGE!!!!



mine was almost the thickness of a piece of paper

"Copy paper is about 0.004 inches thick" or 0.1 mm





so i wonder - should i discard that round?


at least not fire outa glock! LOL

 

[jamz]

Good info, I thought it was common practice to chamber a different round if possible.

 

[Ducman]

god damn 1/10" is almost a full 1/8" - thats HUGE!!!!



mine was almost the thickness of a piece of paper

"Copy paper is about 0.004 inches thick" or 0.1 mm





so i wonder - should i discard that round?


at least not fire outa glock! LOL

I wouldn't fire it out of a Glock anyways

 

[MrMcCrackin]

I wouldn't fire it out of a Glock anyways

i agree - maybe i will send it to you to fire then?