someone explain this! case dent after firing

[RU shooter]

Riddle me this Batman, I was out shooting my M39 this morning and using my normal favorite load of a lee 312-185 w/gc over 30 grs of pulled Russian powder, I fired about 15 so far and then out pops this case with a huge dent from the base of the neck down approx 3/4-1" and atleast 3/16 deep???? Nothing was out of the norm. and even the boolit went into the same group .
So I check the chamber real good ,nothing unusual ! fired about 2 more rds. without incedent and I get the second dented case,What is going on here???? Same exact place same exact size same shape !!!! I had fired about 30 rds of a different load before shooting this load and then fired about 20 J word rds after the dented case load and nothing unusual at all! I have had this rifle for about 5 yrs now and fired countless rds without a single issue! What would cause this? how do I prevent it from happening again? This is about the strangest thing I have seen in my 20 some yrs of reloading.

[JSH]

I have seen this before. You are shooting the boolit so fast that the vacum sucks the brass in.
Sorry had to do that. Told a fellow that a few years ago and had him believeing it,lol.
How many times have those cases been reloaded. I would say that the necks are getting hard and letting the gas blow back down between the chamber and the brass. May be time to anneal.
But on the flip side, I did see one fellow have this happen after annealing. He annealed way to low and didn't do the neck. Which in turn made it worse as the case body was to soft and the neck to hard.


Jeff

[SharpsShooter]

I have seen this before. You are shooting the boolit so fast that the vacum sucks the brass in.
Sorry had to do that. Told a fellow that a few years ago and had him believeing it,lol.
How many times have those cases been reloaded. I would say that the necks are getting hard and letting the gas blow back down between the chamber and the brass. May be time to anneal.
But on the flip side, I did see one fellow have this happen after annealing. He annealed way to low and didn't do the neck. Which in turn made it worse as the case body was to soft and the neck to hard.


Jeff

Yep, the crimp is so tight the boolit tries to drag the brass along[smilie=1:

Time to anneal or replace the brass

SS

[TAWILDCATT]

NORMALY i WOULD THINK IT WAS MADE WHEN THE CASE WAS EJECTED.however the dent is too rounded it looks like the gas is getting between the case and chamber.however did you get gas in your face or see it out of breach.did you check your loaded shells. after that who knows?

[S.R.Custom]

... I would say that the necks are getting hard and letting the gas blow back down between the chamber and the brass.

Ummm... for that to happen there would have to be more pressure outside the case than inside...

[Bent Ramrod]

I believe it's a kind of reverse obturation; if I recall it also happens occasionally in well casings when an explosive is used to cut the casing to let in the oil at multiple levels in the well. Some of the gas pressure gets in between the rock and the casing (or between the chamber wall and the brass shell) and as the pressure drops inside the borehole (or the bore), the trapped gas pressure pushes the metal into the low-pressure central area. I don't think this is anywhere near the working pressure of the powder, but it doesn't take a great deal to push unsupported thin metal, forming a dent.

I would guess that your load is lower-pressure, not allowing the case to totally expand against the chamber wall. If the case is work-hardening, as JSH suggested, this could aggravate the condition as well.

[SharpsShooter]

Super,

If the work hardened case neck does not fully expand to seal the chamber then pressure is applied to the exterior shoulder of the case following the boolits departure from the case and continues until the boolit exits the bore. The case neck is often work hardened due to sizing and expansion during firing, leaving the shoulder and case body relatively soft and in some cases (pardon the pun) vulnerable to pressure deformities from gas blow by from the unsealed neck. Often the shooter gets a face full of gas and small particles or oil from the bolt itself.

SS

[RU shooter]

The brass I was using was all reloaded 6-7 times and the theroy of gas getting between the case and chamber does seem logical except if its because of too low of chamber pressure in that specific load why didnt I have any issues in the other loads I shot earlier 8 and 12 grs of 231 with a 155 gr boolit (alot less pressure there) And no I didnt recall any gas leakage from the bolt I did with the last load I shot 20 grs of 2400 and Jwords but only on one or two rds and very mild amount.

[trk]

It's gas leaking back around the neck between the case and the chamber. The case empties of pressure once the bullet passes out the barrel the case caves.

Some folks prevent this, and getting the soot from blowby, by leaving just a LITTLE flair outward on the neck. (Doesn't help much on crimping.)

I would also agree that if the brass was softer it would seal better. I've only had it happen once - and then I switched to neck sizing only half way down the neck.

[felix]

231 is a fast powder. ... felix

[BruceB]

When my wife's beautiful Browning Mauser blew up, the recovered case exhibited a shoulder collapse much like the one illustrated. It was BIG!

It is my firm belief that there was a HANGFIRE, because the bullet traveled only about four inches from the case, and stopped.

I envision this in the case of Karen's Browning:

-the primer fires, and a part of the load ignites, driving the bullet out of the case.

-the bullet stops as the powder load fizzles, and since the pressure is NOT sufficient to seal the chamber, some gas comes back outside the case and collapses part of the case. Note that this now also replicates the well-known circumstances for SEE, as well.....namely, a decreased load of slow-burning powder in a much-enlarged volume.

-the powder finally gets burning, and the pressure behind the bullet, both inside the case wall and outside the case wall are identical, allowing the collapsed area to remain in its collapsed state.

-in my wife's rifle, the pressure generated was sufficient to DESTROY the rifle, even while the case collapse remained.

I strongly suspect that the rifle in the current thread has been hangfiring, even if the hangfires are too short to be noticed. I would view those collapses as a very serious WARNING to change the load rather drastically. For openers, I'd use a dacron filler, at least, but also I'd be inclined to use a powder load of known characteristics (meaning, published loads with U.S. powders) and see how well they work in the rifle.

I doubt that work hardening has anything to do with this event. Even work-hardened brass isn't all that hard, and in my wife's rifle, the case was once-fired only, meaning there was no possible effect from work-hardening.

[44man]

I can't disagree with a thing Bruce says! Sounds like one step away from a blown rifle. I would use the remainder of the powder for fertilizer.

[1hole]

Bottom line is your chamber pressure is too low to expand the cases and seal the chamber properly.

It may be agrivated by work-hardened necks or a different lot of powder or ..... other mystical factors. But that doesn't change the fact that your pressure to simply too low to effect a seal.

[JSH]

Fellows, what I was going on was experiance I had. Almost the same thing, but the dents were not quite as bad. Now that Bruce mentioned the hang fire, I remember seeing that once before on a rifle at the club a gent was shooting. I don't recall make or caliber, but the dent sure looked like the one in the pic.

What I had experiance with was a 7BR and a 7TCU. Sooting and so forth all the way back to the action face and bolt face. Not a bit of smoke came out around the action. I annealed all of the cases and problem solved. These were by no means squib loads or light. Then the 6 TCU started showing the same sooting and it had a large dent like a lube dent in it. I susupect that it was because of the case shape as to how the dent was made. Annealed those and problem solved.
The TCU cases had all been neck sized only and had been shot a lot.
I would also suspect the long gradual type taper pf the 7.62x54 would lend itself to "blowby" a lot more so than other designs. I know I know what some of you are thinking. But the 7.62x54 was never intended to be reloaded as were most early designs. I guess some may have just been luckier than others.
Jeff

[DLCTEX]

The three other times I have seen and read of the case denting illustrated in the pics. 231 powder was involved. Coincedence? Light loads not generating enough pressure until secondary ignition is the best guess I've heard. Dale

[texas tenring]

I had the same thing happen with a 91/30 shooting .308 J-bullets and a medium speed powder. It is the neck not expanding to make a seal and letting back presure dent your case. In my opinoin the faster burning powders give you more bang! so to speak and won't give you that problem with a light load. A medium or slow burning powder in a light load won't give enough chamber presure to make the seal. I've not had any problems with cast boolits and 2400 powder.

[RU shooter]

The three other times I have seen and read of the case denting illustrated in the pics. 231 powder was involved. Coincedence? Light loads not generating enough pressure until secondary ignition is the best guess I've heard. Dale This did not happen from my 231 loads these are from a load of 30 grs of pulled powder from russian 54R rds. the burn rate of this powder is between 4895 and 3031 and have used it with good results in other calibers using 3031 data. The avg load from a 150gr ball rd is 47.5 grs .
My load manual states a 44gr starting load for a 180 gr jacketed bullet with 3031,So I am loading these at 2/3 for a 185 gr cast boolit . As stated I have shot atleast 100 rds of this same load with no problems. As far as hangfires I have had them with milsurp ammo and know what they feel/sound like , But these in no way acted like a hangfire. I looked over my other fired cases and there was no sign of sooty necks or cases. I'm not trying to dispell anyones theory just stating more facts So I can get a better grasp on what caused this

[danski26]

I've never seen anything like this before. All the theroies sound possible.

My question with all of them is, how is it the exact same dent in the exact same place?

Hangfire or hardened neck wouldn't the dent be random in size and location, driven by the variables in case construction, hardness level, position of bullet in the bore "mentioned in hangfire situation", exact position of the powder in the case and so on?

[Linstrum]

:confused:I would stop using the rifle and get the chamber Magnifluxed or dye-tested before resuming shooting since a crack in the chamber wall will cause this kind of phenomenon. A crack that starts from the inside at the chamber wall sometimes won’t go all the way through to the outside at first, and if the crack communicates with any gas pressure before the brass seals during firing the crack will harbor gas under pressure like a small air tank. When the pressure in the barrel drops the gas is released back out from the crack and its pressure bulges the case inward.
I hope there is some other explanation, but I have read about this before some time back in one of the gun rags many decades ago, probably in the 1950s. You can get fluorescent dye and magnetic type crack testing kits online now, but I don’t know what they cost. I'd check it out because we are not very often given a danger warning like this that a violent catastrophic failure is about to occur!
Good luck, I hope it is not the worst-case scenario.

[dromia]

This was quiet a common occurence with FNM 6.5x55 Swedish factory ammo, percieved wisdom at the time was slow pressure build combined with brittle brass allowed gas to escape past the neck but the rear of the case had sealed the chamber. No gas escape and the round felt and shot as normal, these cases also universally sooty with the odd shoulder collapse.

[chevyiron420]

there is merit to alot of what has been said here, but, your problem is the powder is too slow!!!!! your max preasure may be normal enough but you have to look at the preasure curve over a time period. time meaning from ignition to the bullet leaving the barrel. the powder is reaching its peak way to late in the burn. you may be able to crutch this by softer brass, heavy crimps, hoter primers, ect. but it still aint right and its dangerous. a jacketed bullet is much harder to push thru the barrel and the powder will build its preasure up in the case, sealing the case tight to the wall before the bullet gets to far down the barrel, and also the powder gets a good effecient burn going for uniform performance. when you use a cast bullet the preasure curve is wrong. it didnt do it before because your close to the edge here. close enough so that one of the variables that others have mentioned was enough to cause it. a good 2400 load would not do this, or many of the other faster powders that i am not experienced with.-phil:castmine:

[RU shooter]

Thanks all for the info , OK now feel free to correct me if Im. mistaken or just plain wrong,I did some reading on previous post about using powders like 4895 in cases this size with similar weight boolits and these powders were recomended in rifles like the garand, 03A3,ect. with cast and even slower ones like 4064 and 4350 with cast from other rifles.So how can it be that the powder I'm using is too slow of burn rate?
Now to rectify my low pressure issue what should I :
Stick to the 30 gr load and use a filler like dacron or whatever that fluffy stuff is?
Increase my charge to maybe 35-40 grs? or more if accuracy stays good?
increase the size of the flash hole slightly?
Or anything else I dont know about?
Basicly how do I increase the pressure? I would like to be able to use this powder as I have a jugs of it and its X ring accurate,and 2400 wont give me a decent group From 15-21 grs Dont know why ,rifle just dont like it! Again thanks for the help,

Tim

[chevyiron420]

tim, i dont mean to come off like an expert here, cause im not. its just i had it happen to me and it didnt hurt anything but a fellow shooter wasnt as lucky! i wont use fillers at all in any cases esp. bottle neck cases. i think that others here do. its not just the burn rate of the powder. some powders are very forgiving thru a wide variation of loading and some arent. you probably dont need to increase the preasure, just get it sooner, so the case seals good. i know there are others here that use these types of powders, so someone else will be better to help you than i am.--phil:castmine:

[leftiye]

RU, You know how many ways to raise pressure? There's a bunch. You'll have to decide which you want to use.

I'm a little sceptical about that powder. I understand you not wanting to waste it, but the writing's on the wall. At the very least, I'd anneal my case necks, and shoulders, plus upping the charge some. If the boolit isn't seated in touch or within a few thou. of the rifling, I'd either make it so, and re-evaluate your powder charge (may cause high pressures), or get another boolit if the present one won't reach the rifling. And I'd also go to a hotter primer, sounds like that powder isn't real easy to light. 1/2 grain dacron is the standard filler. Leave it fluffed up, and filling the whole case above the powder with it (not packed on top of the powder). Only use filler if a major part of the case is left empty after the powder is put in. I don't like fillers either, but they're probably not to be given major worry as to their safety. Just to name a few. I do think Chevy's right about the burning rate being wrong, and the pressure curve peaking too late.

[georgeld]

Interesting.
I've never experienced this, but, I've picked up brass a few times at the range with dents similar to these.

Since you have lots of this powder. What about using it in some other gun/loads instead of this one??? Then you wouldn't be losing it. Might be safer that way. We'd all sure hate like hell to learn you blew it up and got hurt.

Are you crimping the case any? Might try a slight crimp and check that out. I always crimp a little bit since cutting a cuticle while digging in a pocket for ammo and snagged it on a small burr. Crimp is just barely enough to smooth off the edge.

Have you compared the burn rate of this powder to the charts to see how it fits?

Once you get it figured out, please share it with us for the educational benifit.

Seems to me IF the theory of not enough sealing pressure and it gets back along the case. There'd be smoke marks on the brass. Are these as they came out of the chamber? IF so, I don't see any smoke, so that would reject that idea in my notion.

Is this a bolt gun as I think it is?

Good luck, be safe,

[Bass Ackward]

Thanks all for the info , OK now feel free to correct me if Im. mistaken or just plain wrong,I did some reading on previous post about using powders like 4895 in cases this size with similar weight boolits and these powders were recomended in rifles like the garand, 03A3,ect. with cast and even slower ones like 4064 and 4350 with cast from other rifles.So how can it be that the powder I'm using is too slow of burn rate? Tim


Tim,

After a long scientific explanation, it comes down to bad air. You must live in WestMorland county. What it amounts to is I am breathing and shooting up your oxygen. :grin:

There are all kinds of things you can do. I would use Winchester primers for squib stuff. They burn a little hotter and a little longer to better ignite their entire powder line which are older generation balls. Then if you need another option anneal. Don't matter how many times you reload, brass will harden sitting on a shelf. Might be you got older brass to start with. I got some unfired Starline given to me. 2 of the first 6 split the entire length from case mouth to rim on the first shot. I'd say I might have to anneal.

[44man]

Brass is funny stuff! Back when 6.5 X 55 brass could not be found I made some from 30-06 brass. New Rem cases. I annealed them, formed and annealed again. They shot good but then I found real cases and left the Rem stuff sit a few years. I found half had split necks from sitting. These were loaded rounds.

[RU shooter]

Tim,

After a long scientific explanation, it comes down to bad air. You must live in WestMorland county. What it amounts to is I am breathing and shooting up your oxygen. :grin:

There are all kinds of things you can do. I would use Winchester primers for squib stuff. They burn a little hotter and a little longer to better ignite their entire powder line which are older generation balls. Then if you need another option anneal. Don't matter how many times you reload, brass will harden sitting on a shelf. Might be you got older brass to start with. I got some unfired Starline given to me. 2 of the first 6 split the entire length from case mouth to rim on the first shot. I'd say I might have to anneal. Thanks and No I actually /Unfortunately Live in Fayette Co.:( The air and everything else is far worse than Anywhere else!!!!!!

[TAWILDCATT]

I load military cart with 13 gr red dot and 170 gr 311291.cronograft at 1680 fts in 1903 springfield.also same load in other miltary rifles.bullet size acordingly. one of the post mentioned the same load.you are playing with an unknown powder and could get in real trouble.if your looking for loads in the 1600/1800 speed i would change powder.there is cheap and there is cheap.

[ARKANSAS PACKRAT]

I had one of these shoulder collapse incidents with a .264 Win. I had some neck cracks, so I sorted the brass, trimmed and annealed the necks. With the first full power loading, (61gr surplus 4831 120 Sierra???) two cases collapsed, normal shot otherwise, no gas leaks, shoulder and neck soot covered. Never had another, surely not from reduced loads in my case. I suspected that I had annealed too far down the shoulder? Still a mystery to me.
Nick

[Larry Gibson]

RU shooter

BruceBs explanation along with points made by others are correct. It was almot an SEE scenario. Regards the use of 4895 vs the milsurp powder you are using; 4895 in reduced loads is very ignition friendly. Many powders are not including many foriegn powders. Has to do with he chemical composition and the amount/type of retardents used. This is why many powders are no recommended for reduced loads. I've used several hundred pounds of 4895 over the years with complete success. I've not had consistant ignition with most foriegn (flake type combloc especially) powders in reduced loads with cast bullets. I would suggest you discontinue the use of that powder for reduced cast loads.

Larry Gibson

[Molly]

I've seen this on a number of ocassions. In my experience, there seem to be two causes, which may or may not work in tandem: Both depend on unburnt powder granules being caught between the case and the chamber. This provides a site for the collapse. If the case fails to obturate, gas can leak down the side to the site of the powder granule. There it may or may not ignite the granules, but in any case, there is still substantial pressure trapped between the case and the chamber when the pressure inside the case drops off. This pressure then expands to cause the side of the case to cave in.

I have also seen it with good obturation and lots of unburnt powder. It seems that the trapped gunpowder can be ingited by the heat transmitted through the thin case wall. The burning powder similarly provides pressure to colapse the wall of the case when the internal pressure drops.

It has been my experience - FWIW - that the problem goes away when powders that are reasonably well suited for the case are used in loads that develop at least moderate pressures.

[Rando]

Former Westmoreland County resident myself, Youngwood (near Greensburg).

Oh, the brass? Almost looks like too much lube on resizing. You would have noticed that, though.