Crushed 7,62X54 brass

[Kegcaissy]

Hi!

While shooting my finnish mosin with unique and 155gr cast, as usual, i've found these dents in my brass. All the cases were fired in the same gun but some of these have this big dent in it. What is happenning?

Here's my recipe:

Lee 312-155gr, WW, Aluminium GC, 10gr Unique.


Here's the brass cases:

http://i1383.photobucket.com/albums/ah294/Kegcaissy/B30C5092-064A-4864-8927-B731587BE941_zpsvawxhjnw.jpg (http://s1383.photobucket.com/user/Kegcaissy/media/B30C5092-064A-4864-8927-B731587BE941_zpsvawxhjnw.jpg.html)

http://i1383.photobucket.com/albums/ah294/Kegcaissy/D36EF15A-F3A1-4DA0-A6C3-FF38C0506F41_zpsbffxjvm7.jpg (http://s1383.photobucket.com/user/Kegcaissy/media/D36EF15A-F3A1-4DA0-A6C3-FF38C0506F41_zpsbffxjvm7.jpg.html)


Thank you

[gpidaho]

Kegcaissy; Got me on that one. I shoot that same load in my Polish M39 and have never had that happen. I'm using PPU brass. Gp

[popper]

Lube dent?

[Omega]

Never had it happen, but read this: http://www.calguns.net/calgunforum/showthread.php?t=300371


Below is a photo of a wildcat cartridge that was fired with too mild a fire forming charge. The left case is properly formed. The cartridge is the .35-348 Winchester Ackley Improved. In firearms, brass cases are just metallic balloons.


http://i274.photobucket.com/albums/jj241/Wrangler-John/AckleyBrass.jpg

Because the charge did not produce enough pressure to force the case against the chamber and create a seal, gas leaked back from the neck and dented the case. Both cases could be reloaded and fired, but they make better examples of what pressures that are too low can do. The case is rimmed, so it headspaces on the rim. It was fired in a Siamese Mauser so there was little danger.

This is the same mechanism that certain semi and fully automatic roller locked delayed blowback actions use with fluted chambers, such as the HK G3/HK91. Gas enters along the chamber flutes as the action unlocks and helps extract the case. Every case fired in these rifles is dented as part of firing.
Could be the same thing happened in your case.

[higgins]

Possibly low pressure allowing gas to leak around the neck. Were the cases smudged with powder residue in the neck and shoulder area?d

[BigMagShooter]

I know! You used such a small amount of powder that when it burned up the bullet still had to make it out the barrel and it created a vacuum and sucked in a dent in the case.... :) how's that... :) I got some ocean front property for sale in Arizona....

[skeettx]

Pressure leaked by the neck and dimpled the shoulder, increase pressure.
Either seat the bullet out into the lands, or increase powder, or use larger diameter bullet
Mike

[swheeler]

Pressure too low to seal neck to chamber, then gas flows back around outside of case. Sometimes when this happens you get a little puff of gas in the face too.

[Josh Smith]

Hi!

While shooting my finnish mosin with unique and 155gr cast, as usual, i've found these dents in my brass. All the cases were fired in the same gun but some of these have this big dent in it. What is happenning?

Here's my recipe:

Lee 312-155gr, WW, Aluminium GC, 10gr Unique.


Here's the brass cases:

http://i1383.photobucket.com/albums/ah294/Kegcaissy/B30C5092-064A-4864-8927-B731587BE941_zpsvawxhjnw.jpg (http://s1383.photobucket.com/user/Kegcaissy/media/B30C5092-064A-4864-8927-B731587BE941_zpsvawxhjnw.jpg.html)

http://i1383.photobucket.com/albums/ah294/Kegcaissy/D36EF15A-F3A1-4DA0-A6C3-FF38C0506F41_zpsbffxjvm7.jpg (http://s1383.photobucket.com/user/Kegcaissy/media/D36EF15A-F3A1-4DA0-A6C3-FF38C0506F41_zpsbffxjvm7.jpg.html)


Thank you

Hello,

Mark the remaining loads so you know where 12 o'clock is. Make sure you clock 'em in the chamber the same each time.

After firing, observe where the dent is in relation to the mark.

While I agree that it's a low pressure issue, the low pressure may also be revealing a chamber abnormality that you might need to address. Or it might be fine, but check out out.

Regards,

Josh

[JSnover]

I'll buy the light charge theory. 10 gr of Unique shoots good in almost anything but that 7.62x54 case is pretty roomy. Bump the charge up a little would be my first choice.

[bouncer50]

I been reloading for over 30 years. Weird part out of 12 rounds 6 round have a dent in the case. if their a problem with the chamber all of them would be dented.?

[17nut]

Anneal necks and it will go away!
Bullet get started down bore and unburned powder gets blown up past neck and down between chamber and not expanded case (neck). Pressure rises and powder cernal burns by itself creating larger pressure than in the case. Pop "lube" dimple.

Trust me, anneal and it will go away ;-)

[Josh Smith]

I been reloading for over 30 years. Weird part out of 12 rounds 6 round have a dent in the case. if their a problem with the chamber all of them would be dented.?

Hello,

I'm only supposing that because the charge is low, it may be leaking at a slightly oval part of the chamber.

It wouldn't manifest itself with all rounds or all loads.

It wouldn't hurt anything to mark the cases, and if the dent is consistently in one spot and especially if that spot isn't 6 o'clock, then maybe it may be beneficial to Cerrosafe the chamber to get more information.

I'm not trying to say that it's dangerous.

I would be interested, however, in whether these cases are fireformed or full length resized.

Regards,

Josh

[Josh Smith]

Anneal necks and it will go away!
Bullet get started down bore and unburned powder gets blown up past neck and down between chamber and not expanded case (neck). Pressure rises and powder cernal burns by itself creating larger pressure than in the case. Pop "lube" dimple.

Trust me, anneal and it will go away ;-)

I was once playing with the Gewehr 88/05 "S" using jacketed bullets.

As you may know, the original diameter built of the 8x57 was 0.318" and later increased to 0.323".

The Gew88 was chambered for the 0.318 version.

Later, at almost the same time, they were converted to take stripper clips and the new 0.323 spitzer round in 150grn. They did this by making them into squeeze bore rifles: The bullet swaged down in an elongated throat.

Anyway, I was trying 0.318 Woodleigh bullets. This created very low pressure, and I got puffed in the face and sooty cases.

I annealed 10 cases - I cooked the necks, no spring left, dead soft - and I had no more gas coming by. The primers still raised up, though.

I do not know how long those softened cases would have lasted as I switched to 0.323 shortly afterward and crushed the softened cases.

Regards,

Josh

[Kegcaissy]

Thank you guys!

[Kegcaissy]

Hello,

I'm only supposing that because the charge is low, it may be leaking at a slightly oval part of the chamber.

It wouldn't manifest itself with all rounds or all loads.

It wouldn't hurt anything to mark the cases, and if the dent is consistently in one spot and especially if that spot isn't 6 o'clock, then maybe it may be beneficial to Cerrosafe the chamber to get more information.

I'm not trying to say that it's dangerous.

I would be interested, however, in whether these cases are fireformed or full length resized.

Regards,

Josh

Hi!

All the cases in that caliber are full lenght resized as i shoot these in 2 different rifle.

[Dan Cash]

Gas dent. Insufficient pressure as bullet leaves case; gas flows back around outside of case colapsing it; pressure finally builds to expand case.

[tomme boy]

It is a low pressure effect. And annealing is just a bandaid. I bet your throat is worn and really long too isn't? You need to increase the amount of powder or switch to a more appropriate one.

[dogmower]

I think those cases may be defective. send them to me for safekeeping :kidding:
low pressure

[Tackleberry41]

I had a mosin do a similar thing, it wasn't low pressure, they were full power. Only did it with some charged with R7.

[Josh Smith]

Hello,

Some Finnish Mosin barrels were originally chambered to use a smaller diameter bullet in the 7.62x53r load. While generally interchangeable, there *are* differences between the 7.62x53r Finnish and 7.62x54r Russian rounds.

These were later opened up (though some were missed) to use the Russian stuff in emergencies.

The bores were still generally tighter than their Russian counterparts. The throats are what were opened up, sorta like the Gew88 with the introduction of the 8x57is.

Regards,

Josh

[tomme boy]

The reason I asked for the condition of the throat. I have had it happen with jacketed on one with a very long throat and the bullet seated too long. The Mosin and the 303 Brit both have this problem. Seat the bullet deeper and use a more appropriate powder and or bullet and it will go away. The bullet is out of the case and the pressure is still rising. But sense the bullet is gone and not helping to seal the case the gas goes out around the neck. In that millisecond that the bullet hits the rifling, the pressure will give a little spike and that is when the rest of the case MAY seal. But you may get a face full of gas too.

[Ken in Iowa]

The reason I asked for the condition of the throat. I have had it happen with jacketed on one with a very long throat and the bullet seated too long. The Mosin and the 303 Brit both have this problem. Seat the bullet deeper and use a more appropriate powder and or bullet and it will go away. The bullet is out of the case and the pressure is still rising. But sense the bullet is gone and not helping to seal the case the gas goes out around the neck. In that millisecond that the bullet hits the rifling, the pressure will give a little spike and that is when the rest of the case MAY seal. But you may get a face full of gas too.


+1 I wonder if a 200 gr or so boolit that fills that Finn throat would be best.

[Black Beard]

Maybe a strong crimp will increase the pressure before the bullet starts moving and help blow out the case to chamber size.

[tomme boy]

The throats were opened up for the D166 bullets. That bullet has way more bearing surface forward of ANY Russian round. And it was also a 0.309" back then. I have a couple rounds of Finnish and they are of two different types. One is the D166 and the other is S 25. And a couple that I can't remember the name that they took the D166 bullet and did not make them with the rebated boat tail. This was a war time thing to reduce the use of materials.

And yes a 200 gr or even heavier will stop this. Or even a mag primer. Or seat the bullet deeper. The gas PSI need more time to rise before the bullet clears the case mouth.