Potential danger associated with a bullet sitting deeper in its case

E

Emin

New member
I have a few rounds of CCI .40 S&W 180 gr TMJ that misfired and had to be extracted from the chamber by racking the slide (I kept them for reference to see the pattern of the firing pin indentation mark on their primers). What really bothered me is that suddenly I noticed most of them had bullets sitting much deeper than normal "unhandled" rounds.

My quesion is how dangerous these rounds become? It seems to me that it probably happens frequently when a round is sent to the chamber -- we're simply not aware of it since it fires afterwards. Would aluminum cases be the reason for bullets being held weaker than the real brass cases hold them? If so, should I avoid CCI Blazer?

Most of you will tell me Blazers are probably the most popular rounds, that all the folks use them with no problem, but still, is it a potential kb! waiting to happen I'm dealing with here?
 
Hi, Emin,

Yes, brass holds the bullet better than aluminum.

No, there is no great danger in a pistol if the bullet is pushed into the case, but accuracy and consistency may not be good.

Bullet setback can be caused when the round goes into the chamber, and also in the magazine due to the gun recoiling and the cartridge trying to stay in one place (that guy Newton gets around!).

But, why the misfires? It sounds to me like a bad lot of Blazers. I willingly admit I don't like them and never use them, but some folks have to.

Jim
 
Jim,

Read my post on Steyr M40 -- unfortunately, Blazers have nothing to do with it (I wish it was that easy). I've used them in various pistols without a single problem. And they seem to be quite accurate too. But most importantly, they're probably the cheapest factory manufactured rounds for practice -- I purchased my last case of 1000 180 gr rounds for $163 including shipping.

My newly-purchased M40 had some problems with the firing pin. It's being repaired at GSI now.

As to my concern about the rounds becoming dangerous if their bulllets are pushed in, have you read this article?
http://www.greent.com/40Page/ammo/40/180gr.htm


Thanks for the info.

[This message has been edited by Emin (edited January 10, 2000).]
 
Bullet set back CAN dramatically increase pressure in the case and give you a potential problem. This is particularly true in 9mm where case capacity varies from mag to mfg. DO NOT shoot a round that is visually "set back" in its case.

I have never heard of factory ammo of any kind doing this.. is it possible your gun is locking up/ binding out of battery, pushing the bullet back and when the bolt face hits its not hitting square, thus your firing pin may dent the primer without setting it off. I'd have the gun inspected just in case, rather than blame the ammuntion. Polishing the chamber might solve this. Also.. you might run your ammo through a go/no go guage and see if you have a bad lot of speer ammo.

The feed ramp can dislodge a factory crimp too, as i've seen by loading and unloading a particular .45 over the course of a few weeks. Over time the round woud start to back into the case (this was a federal 230 gr hyra-shock). By the time I noticed the problem I'm SURE the bullet was dangerous. So INSPECT your ammuntion once in a while, particularly if you are loading and unloading the same rounds over and over without firing them. Polishing the feed ramp can help this problem.

Hope this info helps,

Dr.Rob
 
DANGER!!!!!!!!!!!!!!

It is incredibly unsafe to fire a "set-back" round, as pressures can run over 100,000 PSI ! (Check past article in AH for test procedure and recorded pressures; 40S&W and 45ACP).

Crimp alone WILL NOT hold a bullet securely; case neck tension is required. Utilize a Lee "U" undersize sizing die if you have any doubts.
Crimp is for removing the 'bell' or 'flare' from a case mouth (automatics). Neck tension is what holds the bullet firmly.

Jim Keenan, be careful! Set-back is, IMHO, the most common cause of KB's..........

------------------
"All my ammo is factory ammo"
 
The important thing here is that setback is not limited to .40 S&W or aluminum cases. It can happen with any automatic pistol.

When the slide strips a round from the magazine the bullet is going to hit the feed ramp. If it doesn't transition smoothly into the chamber it is surely possible for setback to occur.

Actually I think it happens more often than we know. After all, how often do we unload the gun and examine the round that was in the chamber.

Bullet pull, crimp and mouth sealers help take care of the problem and normally there are no troubles. One area where this can be a big problem is with law enforcement officers who load and unload their weapon every shift. After just a couple of days of that the chance of setback is much greater.


To answer the original question I don't think Blazer is too different than brass in bullet pull. My suggestion would be to call CCI- the 800 # is on the box. Have the lot number of the ammo in question.
 
Thanks one and all for reminding me of a potentially serious problem that I had forgotten about. I knew to rotate a round that you had previously chambered, so that the extractor had a grip on a "fresh" section of the case rim. Certainly it is know longer worth a disaster. "Once" chambered rounds will now be relegated to practice sessions.
 
Wish I knew how to post a picture of the exploded barrel that resulted from a setback .400 Cor-Bon cartridge. Heck yes, setback can cause a Kb.
 
Was wondering is there any "correct" way to test the "crimp" on reloaded ammo? My "method" is to take a just loaded round and with the thumb attempt to drive the bullet into the case by pushing it into the bench. "I often use the entire hand" If it stays solid I consider it fine and leave the setup as it is.
I also when first reloading 45acp took the firing pin out of a 1911 and hand cycled a mag full a few times then checked the ammo. No noticeable set backs. "Didn't mic them"
Anyone got any better ideas?? I bought some "professional" reloads and darn near blew up my gun. Bang, bang,bang, BOOOOMMMMM!! I "tested" them in the way I described above and the bullets would set back. :( I had bought 500rds from a place that provides ammo for the Law Enforcement Training school. They did give me my money back and my gun was fine. "Darn near magnafluxed it"
 
BS Alert!!

The Charles Petty article from AH generated those astronomical pressures NOT from in situ, but from a computer program which more or less extrapolated the pressure figures based on who knows what mathematical model(s).

YES, setback can give rise to dangerous pressures. But it also is often accompanied by loose neck tension (pressures go down), lots of room for gas and powder blowby past the bullet before it gets back forward to the throat (pressure goes down), and perhaps other variables I can't remember.

Based on reading too much, MHO sez setback is most dangerous with fast-burning powders, heavy bullets, and loads that are on the ragged edge of being overpressure in the first place.

Setback that's equal to the thickness of a business card or two are very UNlikely to result in danger in a reasonably strong gun firing reasonably safe ammo (like the "big boys'" factory stuff, the infamous lot of Federal 180-gr Hydra-Shoks excepted).

Absent an intertial bullet puller to put the bullet back forward to more than Min OAL, you could tape it to a long stick (bullet toward the end) and vigorously swing the thing to try to move the bullet forward...maybe it'll work, maybe not.
 
Cheapo, (& not a flame but an observation)

"generated those astronomical pressures NOT from in situ, but from a computer program which more or less extrapolated the pressure figures based on who knows what mathematical model(s)."

May be, but too, consider the effect of placing same load of a safe .357 loading into a .38 Speacial case. This is a pretty far "set-back" (.1" which is HUGE)) but does illustrate the disadvantages of reduced case capacity. Safe in .357 case will cause drastic pressure increases in a .38 spl case. Same with set-back to varying degrees depending upon case volume. 9mms are supposed to be very sensitive to even .030" depending upon load & bullet.

"But it also is often accompanied by loose neck tension (pressures go down)"

Loose neck tension in a semi-suto is what causes (allows) set-back when round is chambered. Feed ramp engagement & bullet gets set back (due to loose neck tension), causing lower volume in case = higher pressures. Progressive powders are exactly that. Lower volume = higher flame temps = higher pressure sooner.

"lots of room for gas and powder blowby past the bullet before it gets back forward to the throat"

I'd say that there is zero blow-by past the bullet as it seals the bore completely. If there's any "instantaneous" (subjective in time, of course) blow-by, it would be past the brass that hasn't a chance yet to expand fully and seal the chamber. Pressures don't build up (substantially) until the bullet engages the rifling causing the "back pressure" against the brass. The brass is the weak link in internal ballistics & is used specifically to seal the chamber against gas escaping backwards towards the shooter.

I doubt very much that any "swinging" of a cartridge would allow cartridge overall length to be increased. Even a very light crimp would hold a bullet in place for even vigorous swinging. A kinetic puller is certainly the way to go - for ~$20 it's a most welcome addition to (those who do screw up now & again as I most certainly do ;)& :() any reloading bench.

I usually check the taper crimp (emphasis added) for auto catridges by vigorously pushing with full force of hand against the loading bench. Measure THAT cartridge beforehand & again after pushing for crimp. Variance between bullet tips (in same lot - depending upon composition/construction) can cause very difference in measurements.

I'd consider even a .005" (measured across full bullet tip - to capture all tip inconsistancies) set back to cause me to add a bit extra to the crimp die.

& BTW, a mike (micrometer) isn't necessary. A quality dial (or vernier) caliper is sufficient to adequately determine any variance in "before & after" to .001". In fact, a (commonly encountered) micrometer has a rotating spindle which can interject measurement errors whereas a caliper is moreso straight-on & is more user friendly (when used properly - of course).
 
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