Fire forming and primer pockets

[rebeltex]

Since you are using an "unquestionably hot" load to begin with, might I ask if you are using the same lot of powder? If not, maybe you have a lot that is slightly hotter and therefore pushing this already hot load over the top.

 

[fguffey]

Simplistically I have been thinking that while the virgin brass has less capacity before fireforming

I was forming and then fire forming cases for a wild cat chamber, I was informed I was going to render the rifle scrap, I was told, at best, I was into some risky stuff by someone I had respect for. I called Hodgdon, they said I was correct and they understood the Arizona smith's concern.

The load I was using was perfect for forming the cases but the same load could be on the high side after the cases were formed. Like annealing, there are a few rules.

F. Guffey

 

[bigedp51]

OK, interesting replies.

The primers were BR2s

OK, then why can I get 5-6 firings on the brass with exactly the same load if I fireform with a lesser charge first?

I like dkhunt's thought that new brass is soft and needs to work harden, but what other explanation is there?

I did not keep the primers, but they did not pierce the primer pocket itself opened up dramatically.

Some detail for those still interested.

Measured at case head just above groove on body side.

New: 0.X74
FF low pressure: 0.X75
1st "hot" load 0.X76
grows to 0.X775 over next 3-4 firings.
over 0.X775 primer can be almost fully seated with thumb
at 0.X79 primer falls out of case when turned upsidedown

Measured FF cases at same location after "hot" FF attempt

smallest was 0.X80 largest was 0.X83

Drew

If your cases expand .001 after the first firing and continue to expand with each successive firing you are exceeding the pressure limits of these cases. Meaning the new cases may be softer in the base than your other cases. The answer is simple, cut back on your load and stay below the elastic limits of your brass.

Lake City cases are harder in the base than Lapua cases to better withstand the larger chamber diameters of AR15/M16 rifles and machine guns chambers that are .002 to .004 larger in diameter.

CatShooter posted Rockwell brass hardness readings for .223/5.56 cases and the hardest reading were with Lake City cases. I shoot mixed brass in my AR15 carbine for practice blasting ammo and try to keep the pressure at approximately 50,000 psi.

Bottom line, you are abusing your brass with excessive chamber pressures and the primer pockets are stretching.

 

[skiutah02]

Since you are using an "unquestionably hot" load to begin with, might I ask if you are using the same lot of powder? If not, maybe you have a lot that is slightly hotter and therefore pushing this already hot load over the top.

yep same 1lb container.

 

[skiutah02]

Bottom line, you are abusing your brass with excessive chamber pressures and the primer pockets are stretching.

Yes, but why so much from virgin vs. 1x? These were taken from the same lot and likely same box, but I cannot be sure as I weight sorted 300 from same lot.

 

[fguffey]

If your cases expand .001 after the first firing and continue to expand with each successive firing you are exceeding the pressure limits of these cases

If the case head expands .001" during the first firing you have ignored your first warning. .00025 is 1/4 of the .001". If you reduce the load and find the case head expansion is .00025" you are back on track if in the beginning you had a plan.

Then there is that part about

each successive firing

In the old days reloaders understood work hardening, today reloaders fire form a case then neck size it after the next 5 firings then start over by full length sizing with total disregard for work hardening. I find it impossible to start over after the case has been fired 5 times. And the case head does not continue expanding .00025" after it is fired over and over and over.

F. Guffey

 

[mikecr]

Measured at case head just above groove on body side.

New: 0.X74
FF low pressure: 0.X75
1st "hot" load 0.X76
grows to 0.X775 over next 3-4 firings.
over 0.X775 primer can be almost fully seated with thumb
at 0.X79 primer falls out of case when turned upsidedown

Measured FF cases at same location after "hot" FF attempt

smallest was 0.X80 largest was 0.X83

You haven't identified a pressure problem yet.
But you have a [chamber that's grossly oversize] problem for sure.
You're just bringing out the problem at a faster rate with more pressure.

Oh, and brass does not get harder with single sizing/firing. It takes sizing cycles to do this. A sizing cycle is actual yielding in both directions.

 

[dkhunt14]

Every firing, sizing reloading cycle hardens brass. The more times the harder it gets. I agree the chamber is probably oversize but I also believe the loads are too hot. Most match shooters don't hammer their brass as hard on the first firing. They found out it usually lasts longer when they back down a hair. Matt

 

[jsthntn247]

90vld ~2900 in 223

I did it to see if I could get away with it, mostly. "Wasting" barrel life, brass life and components fireforming brass seems wasteful if I could get away with finding a load that works well in virgin brass. Been able to do it with almost all of my calibers/bullets in the past (often different loads in virgin brass vs. 1X+ fired, but I do not normally load hot, just accurate. It is just that this combo is stupid accurate and has low ES, etc but is hard on the brass so I was trying to see if I could get another firing out of it by shooting at a match while fireforming.

Clearly this will not work, but now I am interested in why.

I've just highlighted your problem. That's insane speed and I know first hand b/c I shoot the same combo at 2750 and I have no problem with brass life. When I get above 2800 I get 3-4 firings at most, some are gone in 1 or 2.

 

[JAnderson94]

Are you having any other over pressure signs?

 

[skiutah02]

90vld ~2900 in 223

I did it to see if I could get away with it, mostly. "Wasting" barrel life, brass life and components fireforming brass seems wasteful if I could get away with finding a load that works well in virgin brass. Been able to do it with almost all of my calibers/bullets in the past (often different loads in virgin brass vs. 1X+ fired, but I do not normally load hot, just accurate. It is just that this combo is stupid accurate and has low ES, etc but is hard on the brass so I was trying to see if I could get another firing out of it by shooting at a match while fireforming.

Clearly this will not work, but now I am interested in why.

I've just highlighted your problem. That's insane speed and I know first hand b/c I shoot the same combo at 2750 and I have no problem with brass life. When I get above 2800 I get 3-4 firings at most, some are gone in 1 or 2.

I agree that it is hot, but I can get at least 5 firings at this load if I first fire form (thus 6x fired). The target here at 600 is why I am trying to get another firings out of the brass as this used 6x fired brass. This in one of several examples from different days, etc, so I feel confident as long as it is fireformed first and below 75oC the load is OK. I let some rounds cook on my dashboard in 75+ outdoor heat and the car heater running to test, and nothing out of the ordinary. Not sure about 100 and sun baked, however.

http://forum.accurateshooter.com/index.php?topic=3868830.msg36548444#msg36548444

The ES is about 10 and SD 4. The primer pockets getting loose over 6 firings is the only real pressure sign. Bolt lift fine, rounded primers, very, very faint ejector marks (no ejector in bolt, however).

When I use a different load at 2780-2850 I can get at least 8 firings on the brass (still going). The one-and-done for virgin is what's got me scratching my head.