What causes a case to dent like this?

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  • Last Post 04 February 2010
amb1935 posted this 03 June 2009

I am perplexed and slightly worried.  I have just started reloading for my mosin 91/30, and I ran into a problem.  I loaded up 10 rounds with a low charge and 10 more with a medium to high charge with jacketed bullets (need to get different powder for my casts!).  So, I shoot all 20 rounds, everything fires perfectly fine, but when I eject this case, it comes out dented where the neck and body meet.  This was one of the medium to high charges.  The neck was perfectly fine and no other signs of problems.  I'm just wondering if anyone else has run into this problem.  Just trying to make sure I'm not overcharging.  By the way, this was new brass, never fired.  Thoughts?

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amb1935 posted this 03 June 2009

a side view.  Pretty messed up.  Maybe just a bad piece of brass?

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RicinYakima posted this 03 June 2009

Usually this is caused by gas leakage around the case neck back into the chamber. Once your cases are fireformed, just neck size and everything will be OK. Ric

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hunterspistol posted this 03 June 2009

     If I were to venture a guess, maybe too much oil or case lube when it was ran through the sizing die.  If you have an excess of lube on the case, a full length re-sizing dies will leave a small dent or crease that will destroy the case sometimes although, I've never seen it happen that dramatically! I'm not sure what did that really.

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runfiverun posted this 03 June 2009

i have seen other moisins do this also. i wonder if they might be a bit soft in the annealing on one side. or if the brass is quite a bit thinner on one side causing it to suck in when the brass relaxes.

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amb1935 posted this 03 June 2009

I loaded this ammo with a lee classic loader, no lube. I have a pretty good understanding of physics, and with the rapid expansion of hot gases in the case, I can't really figure out how the case would “suck in” and cause I dent like this. Until I hear otherwise, I think I'm just going to chalk it up to a bad piece of brass. -Ric, I hope that you are right. I have about 80 other new cases to fire, then I will reload the once shot brass and see if any of the other cases buckle like this.

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RicinYakima posted this 03 June 2009

Yep, new cases sized to minimum spec's. I fireform for my M28 Finn with 15 grains of A2400 and a 200 grain cast bullet seated tight into the throat. Ric

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amb1935 posted this 04 June 2009

Thanks a lot, Ric! I really appreciate the feedback!

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303PV posted this 04 June 2009

I have seen this before with a 7.5x55 Swiss case and a reduced charge of a slow burning powder. René Malfatti has a picture of a 7x64 Brenneke case  in his book , Nobelsport Handloading Manual.He says that it is a badly ignited charge and that it mainly happens with ball powders. The 7.5x55 Swiss was loaded with an extruded powder (N204) however. Which powder , load and bullet weight did you use ?

There must be a considerable pressure difference between the outside and the inside of the case to deform it like this.  

 

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amb1935 posted this 04 June 2009

H414, 47gn behind 150gn Sierra Spitzer

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canalupo posted this 04 June 2009

Amb

I would make a mold of the chamber and check it against the brass, new and reloaded. Chamber may not be same as brass or as rifle spec. Some of the mosins used a Swiss round or a Russian round. I may be wrong but 7.62 x 54R means it is a rimmed brass and not a Russian brass.  A friend had the same trouble with a italian rifle. It was supposd to be a Italian carcano round. Turns out it was really chambered for a Argentina Carcano round that was 3 or four millimeters longer. Every round he fired cracked the brass around shoulder area. There is also a 7.62 x 53R round out there that some dealers try to substitute for the 54R brass. The chamber taper may be your problem and not the powder/ bullet combo.

Good Luck

Bob D

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303PV posted this 05 June 2009

Hodgdon lists a starting load of 49.0 grs of H414 for a 165 grains bullet.You use 47.0 grains for a 150 grain bullet. I think this low charge of a slow spherical powder explains the problem.

http://data.hodgdon.com/main_menu.asp>http://data.hodgdon.com/mainmenu.asp

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amb1935 posted this 05 June 2009

303, That is true, but due to the primer shortage I have been forced to use LR magnum primers. The general consensus on here is to reduce load by about 5% to allow for the bigger bang. Maybe I should just ignore the fact I'm using magnums and just stick to the recommended load, but not get within 5% of max load, which I wont be doing anyway.

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303PV posted this 06 June 2009

Amb1935,

Starting load is 49 and max load  is 52 grains. 95% of 52 is 49.4. There is not much margin between starting and max load. But you also use a 150 grain bullet instead of a 165 grain. The calculated pressure with 49.0 grains 150 grains is 33105 psi (CIP piezo) with a 165 grains bullet 36924 psi . (Calculated with Quickload). The Max pressure for this cartridge is 56565 psi. I still think the dented and blackened case is caused by a charge that is too low.  

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giorgio de galleani posted this 06 June 2009

What about headspace,rim thickness& shoulder lenght?

IS THE BOLT NUMBERED & matched to the action?

I think the pressure is too low.and or the powder is too slow.if the primers are ok.

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amb1935 posted this 07 June 2009

303PV wrote: Amb1935,

Starting load is 49 and max load  is 52 grains. 95% of 52 is 49.4. There is not much margin between starting and max load. But you also use a 150 grain bullet instead of a 165 grain. The calculated pressure with 49.0 grains 150 grains is 33105 psi (CIP piezo) with a 165 grains bullet 36924 psi . (Calculated with Quickload). The Max pressure for this cartridge is 56565 psi. I still think the dented and blackened case is caused by a charge that is too low.   Thanks 303, I really appreciate the info. Do you like quickload? Is it easy to use / helpful?

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amb1935 posted this 07 June 2009

giorgio de galleani wrote: What about headspace,rim thickness& shoulder lenght?

IS THE BOLT NUMBERED & matched to the action?

I think the pressure is too low.and or the powder is too slow.if the primers are ok. Yes, all numbers are matching.

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JetMech posted this 07 June 2009

giorgio de galleani wrote: I think the pressure is too low.and or the powder is too slow.if the primers are ok. It's basically both these. H414 is too slow for a 150gn bullet to build sufficient pressure fast enough to expand the case and seal the chamber. Switch to something in the range of H335 or H4895 and I think your problem will go away.

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303PV posted this 08 June 2009

Amb1935,

Yes, I like Quickload very much. It is of course not a substitute for the loading data manuals. It helps a lot with load development though.

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mlr1m posted this 04 February 2010

runfiverun wrote: i have seen other moisins do this also. i wonder if they might be a bit soft in the annealing on one side. or if the brass is quite a bit thinner on one side causing it to s**k in when the brass relaxes.

I see alot of these at the range also after the mosin shooters leave. It must be fairly common.

Michael

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JSH posted this 04 February 2010

I have not seen this happen a lot, but have seen it happen in several different calibers and cases. 3006, 35 Whelan 30-30,308 7.62x54, 22 hornet just to name a few. I have to agree with most of the above. Just not enough presure to expand the brass. FYI, all i mention above that happened were with handloads either using a smaller than normal amount of fast burning powder or samller than normal slow burning powder. One of the guys I shot with is a phsysisit at KU(spelling). I respect his thoughts very much. He is a shooter and not just a talker/thinker. A while back this happened to one gents 03. The laod was below book and he had virgin brass with the bullet seated way off the lands/throat. A pull of the bulleta bit and let the bolt seat it and everything turned around. Pressures were increased in turn. I always found it strange that very few of these rounds did the gases get back to the bolt. I would guess the softer body and shoulder area gave up easier than the web area? I started seating all of my CB's to engage when firforming brass. This does achieve two things. It holds the brass back against the bolt where it belongs, thus keeping head seperations down to a minimum. Also it increases pressures enough to fire form the case very well. jeff

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2Tite posted this 04 February 2010

RicinYakima has it right. It's not the brass. It's blowback from the case mouth from a lack of pressure and actually it's not a particularly bad case of it.

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