There was a thread a while back on dented cases - dents that form in the chamber. What was the concensus as to the cause? It happened to me!

There was nothing untoward - just an ordinary load that worked normally, no excess pressure, nowhere near max loads. There was no debris in the dent. It was just there!

Too much grease on the case while FL sizing ?

Yo - André!

This is normally indicative of using too much lube on the cases when they are sized.

Tends to the shoulder areas of the cases as that's where the lube collects in the F/L Dies as the case is sized.

The dents usually iron themselves out at the next or subsequent firings.

Since each case requires lube - lubing each additonal case will simply add to the lube already accumilated in the Die. Take the Die apart and give it a good clean and then you ought to be back to Step #1; after not using so-o-o much lube on the next batch of cases.

BUT; I've also seen dents in fired cases caused by debris in the rifle's chamber! But certainly not the size of the dent you've got in that particular case.

I would have to agree with these guys. I was dumb enough to get these dents all the time. Finly I broke down and got a RCBS lubpad w/ lube. But I was told by this older guy about other things he uses to lube his case. Clear boot polish i think was one of them I be leave.
No worrys bout that case, the dent will pop right out.

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Originally posted by 303Guy:
There was a thread a while back on dented cases - dents that form in the chamber. What was the concensus as to the cause? It happened to me!

There was nothing untoward - just an ordinary load that worked normally, no excess pressure, nowhere near max loads. There was no debris in the dent. It was just there!

Dented when fired or dented when sized?

Dented when fired! (I did say "dents that form in the chamber" - somewhere in the middle where it got hidden!)

This case has never seen a sizer die - I don't have one!
I had forgotten about this until I reloaded it. This dent looks just like the ones from the previous thread!

Dents caused by lube in the chamber form on the shoulder and have a longitudinal orientation. Dents from debris in the chamber are ironed into the case. Powder granules get crushed and leave a small impression on the case. Small bits of waxy-lube flatten out and leave a small dent which irons out again. The denting agent always remains stuck to the case - until now! (Even oil caused dents will still have oil in them - in this rifle, first time fired cases have a gap at the shoulder as it's a rimmed case).

There's also the possibility of too weak a load to expand the case and obturate the chamber. As a result, gas blows back, smoking and denting the case. Do you remember if the case was blackened after firing ?

There was no sign of gas leaking and the primer showed the same flattening as the other cases. There was nothing in the dent either.

THe case was dented after firing and before its next reloading. This could have come from something like hitting a rock when ejected or any number of other bumps or bruises. A dent like this will not iron out during resizing, but will upon the next firing. Unless it is severe enough to knock the neck out of alignment, it usually has no effect on velocity or accuracy.

I have seen photos of cases dented by blow by from low pressure loads but the dents were usually much worse than you photo.
I think I have even then the entire shoulder telescoped back a bit by the same low pressure phenomenon. What the exact conditions are that cause it I don't know but I believe the photos I saw were with a belted case.
I have never had it happen despite smoking 1000s of cases.

it could be caused by hitting the feed ramp/top of bbl,or bolt lug groove, while being chambered.
and then not being "ironed out" during the low pressure firing.
rimmed cases do have a tendency to "pop" out of the mag when being chambered.

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THe case was dented after firing and before its next reloading.

True, but such a dent will have a mark from what it hit and would not rechamber.

This case came out the chamber like this. I drew the bolt back slowly to catch the case. There is no popping out the magazine of a Lee Enfield.

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I have seen photos of cases dented by blow by from low pressure loads ...

How low a pressure load were those? This one was a normal load - the primer showed no difference from the others I fired. But it was by no means a hot load. It is a 303-25 with a SAAMI max of 43,000CUP and probably not even loaded to that but I cannot say. Why would this only happen once? Why would a low pressure load that hardly shows on a primer have the enough presswure to dent the much stronger case?

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Originally posted by 303Guy:

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THe case was dented after firing and before its next reloading.

True, but such a dent will have a mark from what it hit and would not rechamber.

This case came out the chamber like this. I drew the bolt back slowly to catch the case. There is no popping out the magazine of a Lee Enfield.

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I have seen photos of cases dented by blow by from low pressure loads ...

How low a pressure load were those? This one was a normal load - the primer showed no difference from the others I fired. But it was by no means a hot load. It is a 303-25 with a SAAMI max of 43,000CUP and probably not even loaded to that but I cannot say. Why would this only happen once? Why would a low pressure load that hardly shows on a primer have the enough presswure to dent the much stronger case?

The explanation I have seen is the case mouth does not seal off. I guess air or gas pressure gets trapped in the chamber similar to oil being trapped in a die.

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I guess air or gas pressure gets trapped in the chamber similar to oil being trapped in a die.

The prblem with that is that it need the neck not to seal and a volume of air with some pressure and since the pressure comes from inside the case .... Makes it hard to see. I have wondered whether there is some form of diesel ignition taking place - the volume and pressure has to come from somewhere and it has to be greater than the pressure inside the case?!! I just don't know! Does this sort of thing only happen to rimmed and belted cases (and maybe fire-forming cases)? If the neck does seal and the shoulder gets moved forward, we have compression and maybe the sudden release of internal pressure is enough for 'shock' expansion of the trapped air?

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Originally posted by 303Guy:
There was a thread a while back on dented cases - dents that form in the chamber. What was the concensus as to the cause? It happened to me!

There was nothing untoward - just an ordinary load that worked normally, no excess pressure, nowhere near max loads. There was no debris in the dent. It was just there!

That's what happens when your load sucks.

If you get lots of dents, it is called leprosy, usually caused by spilling powder or cream of wheat in the chamber.

There's little question in my mind that this dent is from too much lube in resizing.....there can be no other explanation....

Dents like those happen when gas flows either from front to back or from back to front. They are there on every case head separation I have ever seen posted




happens when gas escapes out the separation and dents the case escaping to the neck area.

Don't know where but I also saw a thread with a similar dent and it was finally decided that it was a low pressure load where the gas flowed from the front toward the case head.

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That's what happens when your load sucks.

I don't know if my load sucks. It's the one I use 'cause it works for me!

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There's little question in my mind that this dent is from too much lube in resizing.....

This case wasn't resized. Maybe from fluid left in the chamber from cleaning but the gun gets stored muzzle up and the bore gets wiped out before use, as does the chamber. Besides, what happened to this fluid? - there was nothing in the dent when the case was extracted and it came out with the dent up while I was looking at it.

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... happens when gas escapes out the separation and dents the case escaping to the neck area.

Now the part that does not make sense is why the gas would be escaping into a high pressure area? The only case head separations I've had did not show any dents and that was a long time ago. I note that the case shown is a belted magnum. I have speculated that shoulder clearance could be involved. The dent and the separation occuring simultaneously supports that speculation. Head separation can only occure if the case body has expanded to grip the chamber walls so gas leaking as a result of the separation doesn't seem likely. But if the case is not seating on the shoulder when fired, it will expand forward and the head will be pushed back to take up the headspace clearance.

The dent on the belted case is a lot sharper than the one on my case. Also, my case did not separate.

The case head separation happens first in a millisecond before there is enough pressure to seal the chamber and before there is pressure at the neck and travels with the internal case pressure forward and is forced forward from the case sealing to the walls behind it.

Here is a previous discussion. I will look for the one about a reduced load but I don't think it was here, might have been on 24hour.

I've seen more than a few case head separations and have had maybe three or so over the years personally. Never saw a dented case. I would think that in the case of a head separation, gases would flow towards the rear rather than forward.

Dents caused by low pressure
http://www.longrangehunting.co...a-case-damage-16851/

Dents caused by case head separation, low pressure or chamber issues
http://forums.accuratereloadin...=957107241#957107241

The dents are not caused by excess lube, ejection damage or hitting rocks. It happens at time of ignition. I've had it happen more than once and also can supply photos. It always happens very near the shoulder on the case body. I can only theorize what has happened but have no proff. roger

Thanks for finding that past thread, woods. I remember now. This what I said back then;

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In that case, it could be possible for some gas - maybe air - to be trapped in the shoulder free space which could be forced into one spot where it expands back into the shoulder, causing the 'dent', as the chamber pressure begins to fall but is still sufficient to keep the neck and case body well sealed against the chamber? And that is a question - not a statement.

I see most of you pictures have been removed! So, some differences; my case was lubed at time of firing, the case shown in the other thread was bone dry. Both cases showed no sign of sooting in or around the dent. I suspect my first speculation may indeed be the cause - air trapped between the case shoulder and chamber. There is actually a lot of air space around the chambered cartridge so if this gets forced into the space between the shoulder and chamber and the shoulder then gets forced forward by rising chamber pressure, that compressed air could well expand and form the dent as the chamber pressure falls again. By the way, on the few occasions that I had a head separation, there was no sign of gas leak out the rear.

Something else from that thread - Alberta Canuck! I haven't seen any post from him for a while now. Is he well?

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Fired like any other round except that
when i removed the case there was a 1/16 dia hole just below the shoulder.

Actually a hole?!!!

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I'm sure that at some time the pressure in the dent area was larger than the pressure inside the case. The maddening thing is how.

Well, under the premise of my 'theory', the air around the case, including the air space in front of the neck gets compressed by the expanding case and stays compressed because the case has undergone permanent deformation i.e. expansion. If some of the 'air' includes some combustion gasses there would be quite a substancial volume of compressed gas that could expand into a weak spot on the case neck/body area, particularly if there was a small particle of something to aid the process trapped in that spot - or the particle is the trigger in the first place. But this 'theory' requires that the neck remains sealed against the chamber until after the dent forms. Which is what you summed up;

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Now your explanation makes sense. In my case I was using 5020 powder and I'm sure the neck wasn't sealing until after the bullet was slightly up the barrel allowing gas to leak a little past the shoulder. The increasing pressure finally sealed the neck trapping the gas in a small pocket. As the internal pressure began to drop the trapped gas at now higher pressure formed the dent and leaked out into the barrel. I think this is what you were also saying if I read you right. By George I think you've got it.

The difference in case volume and shoulder position between a fired case and a 'new' case can be seen here;

I have a Moisin Nagant in 7.62 x 54R that does this all the time. I thought it was from the bolt hitting the next cartridge in the magazine when a spent case was ejected. I do shoot fairly mild loads, 36gr IMR4895 with a 150gr bullet.

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I have a Moisin Nagant in 7.62 x 54R that does this all the time.

Interesting, Super 88. Do you neck size only or full length size? Head-space on the shoulder or rim? The other thing, do you anneal often? How far past the shoulder? Any idea how much spring back you get on your cases? (Trying to figure out how much air space there might be between case and chamber).
And if I may ask, how well does your Nagant shoot? It's a curious and clever design!

Woods would know what caused these types of dents .

I support his conclusions as well . 303 ; Neck sizing those cases only ?.

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Neck sizing those cases only ?.

Yes, but the case in question is likley a reformed case from 303 Brit so it could have had a lot of chamber clearance - I don't know for sure. There were a few 'new' cases around when I annealed them. This is the first time I have ever seen a case dented in this way and I only heard about them from the previous thread.

That is definitely leakage form a probable light charge of powder. The case in the first pic shows what looks like blackening of the case mouth. This sometimes occurs when fire forming brass with a light load.

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This sometimes occurs when fire forming brass with a light load.

Actually, Bob G, that is the colour of the anealing, or rather, the way it shows up in the pic. That case has been annealed and neck sized since the dent formed. It was definately not a light load. Not heavy either. I had meant to takes pics of the primers of all those fired that day. It was a target session and it was not the first cartridge fired. I was re-sighting the rifle after increasing the powder charge from what I had been using. This load is now near max for the rifle. But the interesting thing is, you said "during firegorming". I think the fire-forming is the cause, not the light charges. The light charges are just what gets used quite often during fire-forming.

I get it now. This is your .25/.303 right.

You neck down the skinny .303 case to .25 cal.
Then you fire it in a fatter .25/.303 chamber.
The neck expands faster than the body and traps air between the chamber and the case body. As the internal pressure drops the trapped air dents the weakest part of the case. When the neck contracts the rest of the trapped air is vented around the neck if it did not leak out past the case head.

Yup. The rear of the case is a neat fit so there is no leakage out there.

Possibly incorrect powder and or charge for the cartridge ?.

I'm simply throwing things out at you to check . I have a buddy who's been loading longer than

even I have . He was having a problem one day at the range with some squirrely loads ??.

Come to find out later he used the wrong powder , those things were all over the target BIG gaps

( Didn't have his dam glasses on when he grabbed the powder

off the shelf and used the WRONG POWDER ) . I now Dbl. check myself and even label the powder

throw with what and how much it's set for with a date !.

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I now Dbl. check myself and even label the powder throw with what and how much it's set for with a date !.

That's good advice! For now I have only one powder and setting I use for that very reason! I tape down the lid on the measure I am not using so as to not 'return' suspect throws from the hornet measure. Emptying the hornet measure is a pain so I tape that up when not in use too. Hornet powder mixed with large rifle powder could be a tad explosive!

But in this case, there was no mistake. The hornet measure has been empty and dismantled for some time. The single granule of powder igniting to cause the dent has not been ruled out but there was no sign of soot in the dent. the case would be expanding quite rapidly and 'hammer' the granule?! Could a granule of powder ignite? Could a granule of powder which has begun to combust be forced back past the neck, get trapped and cause the dent? All of which still requires an air space around the case.

303 Guy
The only time I had something like your cases show happen was due to the bullet being shoved down into the case -- third/fourth cartridge down in magazine. Recoil from shooting did it despite crimping at the shoulder. Remington brass / .375 Wby / W760 / 350-grain Woodleigh load. I stick with semi-compressed loadings, and non-ball powders for shorter bullets. Nice long ones like Barnes, RHINO and so on vs. Woodleigh, Sierra, etc. don't pose the same problem for me.

You may have said it but does the denting happen every time and are you single loading or stacking rounds in the magazine to fire the rounds?

Barry

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Originally posted by 303Guy:
There was a thread a while back on dented cases - dents that form in the chamber. What was the concensus as to the cause? It happened to me!

There was nothing untoward - just an ordinary load that worked normally, no excess pressure, nowhere near max loads. There was no debris in the dent. It was just there!

I've seen case dents from:

• unfired powder in chamber
  
• case hitting ground
  
• lube left on case
  

That looks too smooth for first 2 - Think its most probably lube.

PS: Next time check and clean chamber before firing another round. Should find culprit.

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does the denting happen every time and are you single loading or stacking rounds in the magazine to fire the rounds?

This was single fed during dialing in. It is the only time I have ever experienced this. RaySendero has suggested it is cause by lube in the chamber. I thought this was not the first round fired but if it is caused by lube then it must have been the first round. Now I am not sure. I did look for debris in the dent - it did have a tiny spot of something black and soft which could have been normal 'dirt'. I have had 'lube' dents before but these form on the shoulder itself and lube is left in the dent, which are also much smaller and have sharper edges. Mmmm...?

If my experience with brass is accurate your dent was not caused by any solid debris or powder grains. I have handled thousands of once fired cases and none have had anything like your dent.
Those fired with powder grain in some cases still had the powder grain embedded in them and if not still embedded it left a nice profile of the powder grain or grains. .35 Remington ammo is loaded to such low pressure that once fired brass often has dents from earlier rounds unburned grains around the neck and shoulder.

Considering how you got the dent I may get one with my 6.5X53R Dutch. It starts with the same brass in a chamber that is much larger than .303 British at the shoulder.

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some cases still had the powder grain embedded in them and if not still embedded it left a nice profile of the powder grain

My observation too. One day we will get to the bottom of this!