Case rupture - What did I do wrong??? - Page 6

briandg · August 28, 2016, 11:11 AM

If you reduced your load a bit into the brass this time, that still leaves the possibility that I the charge was wrong, but I'm not buying it.

As was pointed out a number of times, an overcharge would have efficiently burned the charge, not leaving unburned granules in the chamber, a dirty chamber, and light impressions of unburned powder odour a quarter inch from the top of the brass. I'm going to assume that at some time you pulled a load and checked your charge.

To me, there never seemed to be any strong evidence of an overcharge, despite all of the debate about data.

Taken at face value, the obvious answer is that you had about a 15% failure rate with the starline, and the failures were off the scale unusual. That sort of thing should never have happened. Even the toothy, jagged line of that tear is evidence of bad metal.

Everything points to brass that couldn't tolerate the normal things that happen when it is exposed to about 30,000 psi of internal pressure for a few microseconds.

Based on this, I think that it is clear that you didn't do anything wrong. The possibility is really slim. The entire process here points to either bad alloy or annealing, or another mistake in manufacturing.

243winxb · August 28, 2016, 02:51 PM

Op

Quote:

I shot 50 rounds of factory ammo and about 60 rounds of mixed brass reloads without any problems.

Would like to see your new load data. Brass headstamps, powder, powder grains, bullets, primers used. Your thoughts on , if the problem is solved and what corrected the dirt and case separations. Ty.

briandg · August 28, 2016, 04:28 PM

Imo don't waste your time providing that information. All that will do is drag the argument out for another five pages. It is solved out of only a few logical causes of that problem, none fit. You used verified load data. Your loads were within spec . Your brass was new. A reliable gunsmith confirmed that the chamber was dirty, that leakage from the brass probably caused it, your further testing may be inconclusive, but it clearly shows that the brass caused gas leakage that fouled the chamber and the used brass did not. I hope that you enjoy the pistol.

Ocraknife · August 28, 2016, 04:52 PM

Quote:

Imo don't waste your time providing that information. All that will do is drag the argument out for another five pages. It is solved out of only a few logical causes of that problem, none fit. You used verified load data. Your loads were within spec . Your brass was new. A reliable gunsmith confirmed that the chamber was dirty, that leakage from the brass probably caused it, your further testing may be inconclusive, but it clearly shows that the brass caused gas leakage that fouled the chamber and the used brass did not. I hope that you enjoy the pistol.

I think I already provided on Friday anyway. The difference this this time was that my barrel didn't get fouled and I didn't have to stop shooting. The only varible is that I used none of the Starline brass in question I only used factory ammo and once fired mixed brass.

I don't know if it was the brass or not but I'm leaning that way. At this point I'm going to throw out all of the brass in question.

I have a 100 pcs of new Starline that I bought from a different place at a different time that are probably not the same lot, I may give those a try. I don't expect any problems.

I'm still not convinced that max pressure (as measured by some manuals and 9% below max but others) should be considered "overpressure" and certainly not enough to blow cases in half but everyone is entitled to their own opinions.

**Unclenick** · August 28, 2016, 04:53 PM

Late to this game, but a few observations:

First, Mr. Guffey called it right that the "second" line on the case and the site of the separation is where the tapered thickness from the head to the case wall ended. When it went through your sizing die it rebounded slightly more than the thinner brass ahead of it, creating the faint line. I've even seen a few foreign .308 cases that have gradually tapering thickness coming off the web that reaches half way up the case, When these cases form a pressure ring or suffer a separation, guess where it happens? Half way up the case.

Second, because of the taper, unless that is typical for this cartridge, I would verify the case water capacity of the fired Starline brass is no less than in your other brands of fired brass. If it has lower capacity, that will raise pressure.

I agree with the earlier observation of the scuff marks on the case. They look like a case run into a steel sizing die with little or no lube. This suggests extraction under pressure and that pressure is too high at the time of extraction. That could be a gun timing issue, but since commercial loads seem to function well in it, I doubt that is the problem.

Your cases are thinner after firing for the same reason a rubber hose gets narrower as you stretch it. The case is being glued to the chamber wall by pressure and the unexpanded, thicker portion is being pulled on like taffy, narrowing it. Congratulations on have a strong extractor, though.

The dimples are impressions made by unfired grains of powder left behind in the chamber by previous rounds as their cases extracted. The brass is being formed up against them, leaving the small indentations. This tells us the burn is not clean (which you already figured out). That generally means poor or incomplete ignition. This can be because of primer or crimp choices, but in this instance it is because the powder you chose is really a bit too slow for optimum performance at your bullet weight in this cartridge. Further proof of that is the Accurate manual shows 14 fps more velocity from a maximum load of just 8.7 grains Accurate No.5 behind a 180 grain XTP than from its 10.7 grain maximum load of No.7 with that same bullet. The No.7 loads were worked up to make the powder look more versatile, but it's not an efficient load and is wasting all that extra powder weight.

The case scraping marks are partly be due to the load being at the higher end of the peak pressure range for this round, but that doesn't cause the issue by itself. It is the highish pressure in combination with extraction beginning early, before pressure has dropped and given the brass time to spring back. The slow burning powder is going to produce fractionally longer barrel times and more recoil than something faster, like No.5 would do. The added recoil is because of higher muzzle pressure and the extra powder mass being expelled. One result is the slide is going to tend to be pushed back earlier and harder relative to bullet position in the barrel than with a faster powder loaded to the same peak pressure.

I would also check, since the gun is pre-owned, that the mainspring and recoil spring are in good condition and at full strength. Either one being light offers less resistance to the slide coming back, again encouraging earlier extraction.

The issues are probably a combination of things in the above pile. But in the main I suspect, because of good behavior with commercial ammunition, that when you go to a faster powder and work the load up from the bottom number, all the while watching for scuffing of the brass and so on, you'll find the problem clears up.

243winxb · September 11, 2016, 08:30 PM

Same problem , with photos. http://www.thehighroad.org/showthrea...7#post10358627

TheGuyOfSouthamerica · September 12, 2016, 10:31 AM

Ocranife,

I only have experience with 9mm Luger and 9mm Federal Rimmed.
I almost loaded 500 rounds by now of eighter of them and never ever had one single issue.
If your seating depth changes you have to adjust your powder Charge. If case is ruptures it has way too much pressure. Pressure formula is: P*V=N or P=N/V. P=Pressure, N=powder Charge in grains, V= case empty airspace Volumen.
If the seating depth changes to less then the powder has to be reduced since the empty airspace Volumen is less.
The only way the case is rupturing is when there is way too much pressure specially with 10mm, 40 S&W or other high pressure caliber. Obviously the bullet is heavier than in the 9mm Luger and that rises the pressure even further leaving you very small room from within Standard pressure and way too high pressure Spikes.
For example: As I reloaded my 9mm Luger/9mm Federal Rimmed with factory 115 grain FMJ I seated them to 1.145" and loaded 4.0 grain of powder (scavenged shotshell powder Bullseye type). As I started casting lead bullets I loaded the lead 124 grain TC TL Lee bullets with 3.0 grains of same powder and seated them to 1.044" (since cast bullets seat deeper somehow in order to go into battery reliably). There you have my experience. I am sure this applies even more for such an high pressure round as you have way less margin to Play with pressure.

polyphemus · September 12, 2016, 10:53 AM

Quote:

Pressure formula is: P*V=N or P=N/V. P=Pressure, N=powder Charge in grains, V= case empty airspace Volumen.

No,
Pressure is defined as force over a surface,ok?
And the formula is p=F/A
where p is pressure,F is force and A is the area of the surface.
the most commonly used unit(round here) being psi or pounds per square inch.

TheGuyOfSouthamerica · September 12, 2016, 11:36 AM

polyphemus,

That formula was given me by an member on Cast Boolits Forum. That formula may be Ok since it works for me and explains the issue.
It is the formula of pressure in an contained Environment.
You could say P=F/A were F=powder and A=bullet weight.

But in an confined Environment Volumen of case is a cosiderable factor. P=N/V considered bullet weight as an constant and temperature as well.

polyphemus · September 12, 2016, 12:11 PM

Quote:

You could say P=F/A were F=powder and A=bullet weight.

I could not say that because it is plain nonsense.
But you could if it makes you happy.

TheGuyOfSouthamerica · September 12, 2016, 07:03 PM

Polyphemus,

Why would that be plain nonsense? There is some logic behind P=Force*surface area.
You can find it out empirical that P=Powder charge/Volumen of the case.
Charge an 357 mag case with 3 grain of a given powder and charge as well 3 grains of same powder in an 38 spl case and 9mm Luger case. Same powder and bullet weight.
I have tried it. The 357 mag case has absolutely no power nor pressure because of the huge empty (airspace) case. The 9mm Luger has lots of power and normal pressure. All other things equal. Empty airspace is the clue.
Pressure equals as well Power and velocity. More pressure, more velocity and more power.

August 28, 2016, 11:11 AM	#126
briandg Senior Member Join Date: May 4, 2010 Posts: 5,468	If you reduced your load a bit into the brass this time, that still leaves the possibility that I the charge was wrong, but I'm not buying it. As was pointed out a number of times, an overcharge would have efficiently burned the charge, not leaving unburned granules in the chamber, a dirty chamber, and light impressions of unburned powder odour a quarter inch from the top of the brass. I'm going to assume that at some time you pulled a load and checked your charge. To me, there never seemed to be any strong evidence of an overcharge, despite all of the debate about data. Taken at face value, the obvious answer is that you had about a 15% failure rate with the starline, and the failures were off the scale unusual. That sort of thing should never have happened. Even the toothy, jagged line of that tear is evidence of bad metal. Everything points to brass that couldn't tolerate the normal things that happen when it is exposed to about 30,000 psi of internal pressure for a few microseconds. Based on this, I think that it is clear that you didn't do anything wrong. The possibility is really slim. The entire process here points to either bad alloy or annealing, or another mistake in manufacturing. __________________ None.

August 28, 2016, 04:28 PM	#128
briandg Senior Member Join Date: May 4, 2010 Posts: 5,468	Imo don't waste your time providing that information. All that will do is drag the argument out for another five pages. It is solved out of only a few logical causes of that problem, none fit. You used verified load data. Your loads were within spec . Your brass was new. A reliable gunsmith confirmed that the chamber was dirty, that leakage from the brass probably caused it, your further testing may be inconclusive, but it clearly shows that the brass caused gas leakage that fouled the chamber and the used brass did not. I hope that you enjoy the pistol. __________________ None.

August 28, 2016, 04:53 PM	#130
Unclenick Staff Join Date: March 4, 2005 Location: Ohio Posts: 21,063	Late to this game, but a few observations: First, Mr. Guffey called it right that the "second" line on the case and the site of the separation is where the tapered thickness from the head to the case wall ended. When it went through your sizing die it rebounded slightly more than the thinner brass ahead of it, creating the faint line. I've even seen a few foreign .308 cases that have gradually tapering thickness coming off the web that reaches half way up the case, When these cases form a pressure ring or suffer a separation, guess where it happens? Half way up the case. Second, because of the taper, unless that is typical for this cartridge, I would verify the case water capacity of the fired Starline brass is no less than in your other brands of fired brass. If it has lower capacity, that will raise pressure. I agree with the earlier observation of the scuff marks on the case. They look like a case run into a steel sizing die with little or no lube. This suggests extraction under pressure and that pressure is too high at the time of extraction. That could be a gun timing issue, but since commercial loads seem to function well in it, I doubt that is the problem. Your cases are thinner after firing for the same reason a rubber hose gets narrower as you stretch it. The case is being glued to the chamber wall by pressure and the unexpanded, thicker portion is being pulled on like taffy, narrowing it. Congratulations on have a strong extractor, though. The dimples are impressions made by unfired grains of powder left behind in the chamber by previous rounds as their cases extracted. The brass is being formed up against them, leaving the small indentations. This tells us the burn is not clean (which you already figured out). That generally means poor or incomplete ignition. This can be because of primer or crimp choices, but in this instance it is because the powder you chose is really a bit too slow for optimum performance at your bullet weight in this cartridge. Further proof of that is the Accurate manual shows 14 fps more velocity from a maximum load of just 8.7 grains Accurate No.5 behind a 180 grain XTP than from its 10.7 grain maximum load of No.7 with that same bullet. The No.7 loads were worked up to make the powder look more versatile, but it's not an efficient load and is wasting all that extra powder weight. The case scraping marks are partly be due to the load being at the higher end of the peak pressure range for this round, but that doesn't cause the issue by itself. It is the highish pressure in combination with extraction beginning early, before pressure has dropped and given the brass time to spring back. The slow burning powder is going to produce fractionally longer barrel times and more recoil than something faster, like No.5 would do. The added recoil is because of higher muzzle pressure and the extra powder mass being expelled. One result is the slide is going to tend to be pushed back earlier and harder relative to bullet position in the barrel than with a faster powder loaded to the same peak pressure. I would also check, since the gun is pre-owned, that the mainspring and recoil spring are in good condition and at full strength. Either one being light offers less resistance to the slide coming back, again encouraging earlier extraction. The issues are probably a combination of things in the above pile. But in the main I suspect, because of good behavior with commercial ammunition, that when you go to a faster powder and work the load up from the bottom number, all the while watching for scuffing of the brass and so on, you'll find the problem clears up. __________________ Gunsite Orange Hat Family Member CMP Certified GSM Master Instructor NRA Certified Rifle Instructor NRA Benefactor Member and Golden Eagle

September 12, 2016, 10:31 AM	#132
TheGuyOfSouthamerica Junior member Join Date: September 10, 2016 Posts: 846	My personal experience: P=N/V ceteris paribus bullet weight Ocranife, I only have experience with 9mm Luger and 9mm Federal Rimmed. I almost loaded 500 rounds by now of eighter of them and never ever had one single issue. If your seating depth changes you have to adjust your powder Charge. If case is ruptures it has way too much pressure. Pressure formula is: PV=N or P=N/V*. P=Pressure, N=powder Charge in grains, V= case empty airspace Volumen. If the seating depth changes to less then the powder has to be reduced since the empty airspace Volumen is less. The only way the case is rupturing is when there is way too much pressure specially with 10mm, 40 S&W or other high pressure caliber. Obviously the bullet is heavier than in the 9mm Luger and that rises the pressure even further leaving you very small room from within Standard pressure and way too high pressure Spikes. For example: As I reloaded my 9mm Luger/9mm Federal Rimmed with factory 115 grain FMJ I seated them to 1.145" and loaded 4.0 grain of powder (scavenged shotshell powder Bullseye type). As I started casting lead bullets I loaded the lead 124 grain TC TL Lee bullets with 3.0 grains of same powder and seated them to 1.044" (since cast bullets seat deeper somehow in order to go into battery reliably). There you have my experience. I am sure this applies even more for such an high pressure round as you have way less margin to Play with pressure.

September 11, 2016, 08:30 PM	#131
243winxb Senior Member Join Date: July 26, 2011 Location: USA Posts: 1,730	Same problem , with photos. http://www.thehighroad.org/showthrea...7#post10358627

September 12, 2016, 11:36 AM	#134
TheGuyOfSouthamerica Junior member Join Date: September 10, 2016 Posts: 846	polyphemus, That formula was given me by an member on Cast Boolits Forum. That formula may be Ok since it works for me and explains the issue. It is the formula of pressure in an contained Environment. You could say P=F/A were F=powder and A=bullet weight. But in an confined Environment Volumen of case is a cosiderable factor. P=N/V considered bullet weight as an constant and temperature as well.

September 12, 2016, 07:03 PM	#136
TheGuyOfSouthamerica Junior member Join Date: September 10, 2016 Posts: 846	Polyphemus, Why would that be plain nonsense? There is some logic behind P=Forcesurface area. You can find it out empirical that P=Powder charge/Volumen of the case. Charge an 357 mag case with 3 grain of a given powder and charge as well 3 grains of same powder in an 38 spl case and 9mm Luger case. Same powder and bullet weight. I have tried it. The 357 mag case has absolutely no power nor pressure because of the huge empty (airspace) case. The 9mm Luger has lots of power and normal pressure. All other things equal. Empty airspace is the clue. Pressure equals as well Power and velocity. More pressure, more velocity and more power.*