extractor tearing rim
On a cz52 what would cause the extractor to tear a piece of rim off and leave the round in the chamber, if:
*about 25 similar rounds fired ok
*the load was below even the latest, mild, published data and showed no signs of primer flattening or other excessive pressure. It wasn't one of the chamber-bursting loads from back when everyone thought these pistols were made for a "special Czech load."
*The cartridge was only lightly stuck and popped out easily by prying on the rest of the rim with a small screwdriver
*there were no signs of unusual dirtiness and barrel and chamber are basically new. The cartridge didn't have any indentations which would suggest that it obturated against a piece of grit which pinned it to the chamber wall.
*about 25 similar rounds fired ok
*the load was below even the latest, mild, published data and showed no signs of primer flattening or other excessive pressure. It wasn't one of the chamber-bursting loads from back when everyone thought these pistols were made for a "special Czech load."
*The cartridge was only lightly stuck and popped out easily by prying on the rest of the rim with a small screwdriver
*there were no signs of unusual dirtiness and barrel and chamber are basically new. The cartridge didn't have any indentations which would suggest that it obturated against a piece of grit which pinned it to the chamber wall.
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Have you measured those cases to insure they aren't slightly overlength? 0 -
quote:Originally posted by Txs
Have you measured those cases to insure they aren't slightly overlength?
If they had pinched the bullet in the throat, I think there'd be signs of excessive pressure. The case mouth might show stretching and tearing too.
I just resized one of the other cases which was a couple of thousandths longer than the torn one. It showed signs of incipient tearing too. I annealed it first to reduce the springback. It measured 24.75mm/.975".
The load was Starline brass, a 100 gr 312 rainier, 6.5 grains of blue dot, and a cci 200.0 -
My thinking goes to your statement, "the round popped out easily". I'm thinking the gun tried to extract the case too early, while the chamber pressure was still "holding' the case
in. Perhaps a heavier spring is needed?? Not familiar with that gun, but is there a way to check/change cycling timing on it??? Bob0 -
quote:Originally posted by babun
My thinking goes to your statement, "the round popped out easily". I'm thinking the gun tried to extract the case too early, while the chamber pressure was still "holding' the case
in. Perhaps a heavier spring is needed?? Not familiar with that gun, but is there a way to check/change cycling timing on it??? Bob
Don't forget it still had the mass of the slide and barrel to contend with, and a spring needs distance in which to work because the force is like nothing vs the inertia of moving the slide and barrel at high speed.
I doubt it, but I am thinking there's a chance my cases may not be as clean as I thought; perhaps I should wipe them again before firing. Maybe some fine grit like some pumice or some talc got on there.0 -
quote:Originally posted by SoreShoulder
quote:Originally posted by babun
My thinking goes to your statement, "the round popped out easily". I'm thinking the gun tried to extract the case too early, while the chamber pressure was still "holding' the case
in. Perhaps a heavier spring is needed?? Not familiar with that gun, but is there a way to check/change cycling timing on it??? Bob
Don't forget it still had the mass of the slide and barrel to contend with, and a spring needs distance in which to work because the force is like nothing vs the inertia of moving the slide and barrel at high speed.
I doubt it, but I am thinking there's a chance my cases may not be as clean as I thought; perhaps I should wipe them again before firing. Maybe some fine grit like some pumice or some talc got on there.
Along those lines, is the chamber itself smooth and clean?0 -
quote:Originally posted by dfletcher
quote:Originally posted by SoreShoulder
I doubt it, but I am thinking there's a chance my cases may not be as clean as I thought; perhaps I should wipe them again before firing. Maybe some fine grit like some pumice or some talc got on there.
Along those lines, is the chamber itself smooth and clean?
It's shiny. This is a one-slide-stamp gun with a shiny bore.0 -
I see two possibilities,
Headspace, could cause this. Or, age hardening of the brass (the only other way brass can be hardened rather than working it). That is if headspace was still partly the cause.0 -
quote:Originally posted by sandwarrior
I see two possibilities,
Headspace, could cause this. Or, age hardening of the brass (the only other way brass can be hardened rather than working it). That is if headspace was still partly the cause.
*What do you mean when you say headspace could cause this?
*If the brass had somehow gotten harder, it would be MORE likely to extract easily because it chambered freely.
That means if it was harder it would be more likely to spring back a greater amount after the pressure was gone.0 -
Just a thought but did you ever fire Steel case loads in this gun some times the lacquer sort of COOKS onto chamber walls and then grips the following cases so tight it Tears the rim. on top of this even if bore is clean and shines A bore brush most time will not even touch the chamber wall. Thus this lacquer or burnt powder fouling is never cleaned I would take a cleaning brush wrap with 000 steel wool and take strong bore cleaner run the brush just in and out the chamber NOT the bore once it goes into bore it will be reduced in size and not touch the chamber walls. hard brass soft brass is not the problem cases sticking to chamber walls IMHO is the problem. If a case is too big it will not fully chamber. Not be tight only after firing. 0
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