Had a case head separation at the range today

[vranasaurus]

Luckily my wife is OK.

I loaded up 50 rounds for her to shoot in her AR 15 (Stag, Nato Chamber). She fired the first round and the bottom of the magazine shot off, bolt catch broke off, magazine catch broke off. The upper has a bulge and the case from the head up is still in the chamber.

The load was 25 grains H335, CCI 41 primer, 55 gr. FMJ, OAL 2.255". This is a load I have used for awhile and never had any issues. It is a grain under the max in the speer manual as well as .040" longer. Each case was checked in a case guage and none exhibited any signs of failure. The charges were all weighed using my Lyman DPS 3.

Is this just a case of needing to inspect my brass more thoroughly or is there somethign else going on?

My camra is at the office, I hope to get some pictures on Tuesday.

[Crankylove]

Cracked case you missed maybe?

Possible over charge or charged with the wrong powder?

I have done both, while swearing up and down that I it had to be something else.




FYI....W296 dosen't work so well in a .45 Auto.

[Jim243]

Glad to hear eveyone is OK. You didn't say (or I missed it) what bullet you were using!

Can't tell if it was an overcharge or not without that information.

For a 55 grain Hornady V-Max bullet I use 23.2 grains of H335 I only go up to 26.0 grains of H335 for a Sierra 53 grain HP. You should have been OK on 25 grains of H335 unless you were using a heavier bullet. Which is my guess, because of your OAL being 2.255, sounds like you were trying to keep it within the limits of the magazine. You may have jamed the bullet into the line and groves of the barrel, eventhou the Nato Chamber should have been longer than the standard .223 chamber. (you need to check the Max OAL for the bullet you were using with a OAL gauge FOR YOUR BARREL) This could have increased the pressure substantually. I find that my ARs like a 0.050 jump and do not react well to bullets jammed to the rifling.

The other issue which you did not cover is wether you crimped the case to avoid bullet setback in a semi-auto rifle. If you did not crimp, there is a posibilty that the bullet was pushed back into the case when the bolt slamed forward and caused the blowup. You need to check the other unfired rounds and see if they can be pushed back into the case.

Wish I could be of more help.
Jim

PS: It could have been just a bad case with case seperation.

[mehavey]

You also describe the results of an out-of-battery fire and/or immediate barrel obstruction. All other things being equal, you could have literally filled the case under the bullet with H335 (29gr) and only generated 70,000 psi -- unlikely to have blown up the rifle as depicted.

See...
http://www.youtube.com/watch?v=Oh1ly...layer_embedded
for classic example.

I realize that the AR bolt/carrier design is such that the bolt must have rotated long before the firing pin can protrude. (Pull the bolt/carrier group out and try it, you'll see.) But I have also seen an instance of what you see in the video, and an instance wherein the bolt was opening too fast (with high-pressure gas expanding the exposed case head portion just ahead of the web like a balloon.)

Anything you can think of that would have hindered action lock-up?

~~~~~~~~~~~~~~~~~~~
post: Be sure your wife (God bless her) knows she is now a member of a very exclusive survivors club, and that no one on the cocktail circuit can likely match her small talk topic.

[TXGunNut]

I ran into a similar situation recently, thought it was brass fatigue but it turns out my rifle has headspace issues. I'd recommend having that checked in your rifle and discard any brass fired in that rifle, especially if there are some odd-looking lines above the web of the case.

[mehavey]

vranasaurus,

If you have an RCBS precision Mic or a Hornady headspace gauge set, what is the as-fired headspace measurement on your cases as compared to what your FL resizer produces?

[vranasaurus]

I don't have anything to check the as fired head space with.

I tried to push some of the bullets by pressing the tip up against my bench and pressing it with my hand and couldn't get the bullet to go in any farther.

[mehavey]

I don't have anything to check the as-fired head space with.

For all.... If you don't already have, I recommend purchasing one or the other of the following -- especially if shooting an autoloader:

A: RCBS Precision Mic
http://www.midwayusa.com/viewproduct...tnumber=477756

B: Hornady Headspace Gauge set
http://www.midwayusa.com/viewproduct...tnumber=479704

Get the Hornady set if you already have a digital caliper (or get both a caliper and the Hornady set as indispensible tools across all cartridges -- cheap insurance.)

Check the as-fired headspace on a case, and then adjust the lock ring on the sizer to give you a dependable ~0.002" under. Over-working/over-sizing cases fired in a larger/longer chamber (even if still within specs) is the fastest way I know to set up a head separation downstream since the cartridge full-length stretches w/ each firing.

With new brass/or commercial round, no problem even in an max-spec chamber. In fact machine guns are deliberately set up that way. But multiple fully-sized reloadings can eventually really make your day really exciting.

[Farmland]

There are not a lot of facts on this one. However in most of my reading the majority of AR blow ups where due to two reasons. Wrong powder used or over charge.

The only mistake I ever made that came close to blowing up a gun was an overcharge. I swear to this day I checked everything and I was carefully. When I check the reloads I found several that had an overload charge.

I have read about the other issues such as out of battery and head space. However depending on the information read it isn't a fully 100% supported reason for blow ups.n Some even try to show proof that an out of battery can't happen.

I do not have the experience to argue one way or the other on these two issues.

If you search there is a lot of info out there on AR blows ups. Some that I remember the most is using pistol powder by mistake, overloaded factor load, over load by self and bullet stuck in barrel.

I'm not going to guess on yours but like I said thereis a lot of info out there.

[Slamfire]

This case from Scharch split its case head and the AR15 blew its magazine out. Funny darn thing the rifle still fed the next round into the chamber.

Anyway a guy at the match had identical problems with .223 brass from Scharch. Best we could figure is the brass had been cleaned with ammonia at Scharch and that damaged the brass.

Still, based on load charges I think your load was way too hot for your rifle. The case head blew because pressures were too high.

Manuals give guidance. It sounds like you did not develop that load in your rifle but just cut a grain from a manual maximum. Sometimes that works, sometimes that blews the case head.

Maximum loads in my match AR's are grains below manual maximum.

You are lucky that the design of the AR15 protected your wife.

[PA-Joe]

"The upper has a bulge?" Are you saying that the barrel has a bulge? Did you check the barrel to make certain it wasn't clogged before firing it?

[hagar]

CCI #41 primers are HOTTT. Blew a case which I loaded with a safe identical load except I used #41's instead of the Rem 7.5 primers I normally use.

[mehavey]

vranasaurus,

What may be four dumb questions:

1) Have you pulled the remaining bullets and examined the powder to see if it even looks the same as H335 in the can?

2) Have you weighed each of the charges above on a balance beam scale to see if they are really 25gr?

3) Do you (have you) calibrate[d]/check-weight[ed] the Lyman DPS scale each time you start a loading session? How about halfway through/at the end of the session? (I just drop a 40gr bullet into the hopper at the beginning/middle/end to see if it gives me the same reading.

4) Does the DPS drop to the same "light" (-negative) reading when you take the powder pan off to empty it into the case -- each and every time? (and does it quickly return to -Zero- upon empty pan replacement, without "hunting around" ?)

http://www.longrangehunting.com/foru...emaster-25300/

Special Dumb Question:

- Have you weighed the pulled bullets to see if they really are 55gr (on the DPS; then on the balance beam) and do the DPS and balance beam agree?

[vranasaurus]

1) I plan on doing that in the near future

2) I will check them on another scale

3) I calibrated the DPS at the beggining and then roughly every 20 rounds

4) Yes and yes If it starts to deviate I recalibrate

SDQ: No but I will weigh them and let you know

[vranasaurus]

CCI #41 primers are HOTTT.

They are magnum primers and the book recommends magnum primers with H335.

The upper has a bulge?" Are you saying that the barrel has a bulge? Did you check the barrel to make certain it wasn't clogged before firing it?

The buldge is in the upper receiver not the barrel. The barrel has no bulge or obstruction.

[mehavey]

Having done many comparison runs between loads using LR and LRMs, unless you are sitting on proof loads to begin with the changeout is not going to literally blow up one's rifle.

Something else is happening here.

- Obstruction. (BTW, is the barrel clear now?)

- Case head already separating due to repeated oversizing/firing/stretching in chamber. (`Need to get the as-fired vs as-resized measurements. How many reloads and have you run the paperclip test on all cases?

- Out of battery/slamfire (supposedly impossible -- but have you pulled the
firing pin out of the bolt to see if broken?)

- Extraction timing too fast (case head exposed under high pressure... improbable but possible)

- Loadout dramatically over specs for either powder or bullet weight. (55/H335/25 should not ordinarily be an over-the-top/proof load, especially if you have not had pressures sign in the past.)





If you're like me, it's not what happened that disturbs you most. It's not knowing what caused it.

[Brian Pfleuger]

It seems most likely that if there was a defect or damage of some kind that caused the incident then it is MUCH more likely to be an issue with that particular piece of brass than an issue with the gun.

[vranasaurus]

If you're like me, it's not what happened that disturbs you most. It's not knowing what caused it.

That's it.

I believe it was a case of the head already starting to separate and I just didn't catch it.

[mehavey]

...believe it was a case of the head already starting to separate....

Did the cases have a specific original source and/or reloading history?
223 brass "ordinarily" [big quotes there] tends to die from gradual primer pocket expansion.