problem bumping shoulder back

[dmax1800]

Mike,
When I'm shooting regularly and reloading the batch of about 90, I haven't had any problems with bumping the shoulder back. This batch has sat for a few months, that's why I think it age hardened. Maybe just this batch for the 300, but the batch for the 270 did the same thing and I haven't reloaded for the 270 in several months.
I don't think I will have to anneal before each resizing if I'm reloading more frequently than every 6 months.
Anyway, thanks for your help.

 

[Mikecr]

Something in your setup has changed then, or we're missing part of the story, because brass does not self-harden.

 

[dmax1800]

Something in your setup has changed then, or we're missing part of the story, because brass does not self-harden.

I am somewhat new to reloading and you must know a ton more than I do, so I'll bow to your knowledge and experience.
Here's all I know.

I annealed the 90 brass in early January in preparation for getting the gun back from a gunsmith with a new barrel. The brass did chamber in the new barrel with no problems, so I continued to use it.

I loaded some of the brass sometime around March and was able to bump the shoulder back 2 to 3 thou. I loaded some more sometime in April and again was able to bump the shoulder. I used the remaining brass in early May. On Wednesday I was out of brass, so I de-primed the batch with a de-capping die, ran it thru a vibrator with walnut media, run it thru a sonic cleaner and started to size the brass in preparation for trimming it when I couldn't bump the shoulder back. That's when I turned to this forum for help.

My dies have stayed the same, I use the same shell holder, the same press, the same head space gauge and the same process of setting up the sizing die (ie setting the die up for 2 to 3 thou of bump).

My intent is NOT to argue with you, but I can't figure out what would have changed in my setup. If you have any ideas, I'm all ears and would appreciate any suggestions.

 

[SidecarFlip]

I'm in the metals business by profession and the only thing that I know of that aqe hardens is wine and moonshine.

The only way cartridge brass 'hardens' is by working. What occurs is the crystaline structure changes. Annealing re-aligns the grain structure.

It cannot change physical properties (work harden without being worked. That is an impossibility.

Not to be argumetative, but you had to physically alter the grain structure of the brass somehow.

Let me ask you however, did you tumble the brass after annealing for a protracted amount of time and how did you 'anneal the brass'. Annealing brass and actually making it ductile without making it too ductile is an exercise in controlled temperature for a controlled duration. Not enough heat for the correct amount of time may give the physical appearance of an 'annealed' case when, in fact, it's not, conversely, too much heat for a long duration renders the brass too ductile and worthless for reloading.

I'm projecting that you assume it's annealed, when, in fact it's not.

 

[dmax1800]

Let me ask you however, did you tumble the brass after annealing for a protracted amount of time and how did you 'anneal the brass'. Annealing brass and actually making it ductile without making it too ductile is an exercise in controlled temperature for a controlled duration. Not enough heat for the correct amount of time may give the physical appearance of an 'annealed' case when, in fact, it's not, conversely, too much heat for a long duration renders the brass too ductile and worthless for reloading.
I'm projecting that you assume it's annealed, when, in fact it's not.

I used a vibrator, not a tumbler. I vibrated it for about 2 hours, then put it in a sonic cleaner, then tried to size it. I only annealed it after I found out that I couldn't bump the shoulders. After it was annealed, I could easily bump the shoulders back. The brass had only 1 firing since it was last annealed.

I use a propane torch to anneal the brass. I heat the shoulder while turning the brass with a cordless driver. I heat until the case mouth just starts to show the slightest hint of orange, NOT red and quench it in distilled water. I have also used 650 degree tempilaq on the inside of the case mouth as an indicator.

The previous batch of brass had 14 firings with annealing every 3rd or 4th firing with ABSOLUTELY no split or cracked case mouths. Would it last that long if I was not annealing correctly?

 

[SidecarFlip]

Maybe, maybe not as annealing brass, like offhand sharpening a twist drill, is an acquired skill.

I use a Bench Source annealing machine which is basically an interval timed rotary table to control dwell time in the heat source and even then it's a crap shoot about getting it set up that involves logging the parameters for the next session.

Without a hardenss/ductility tester, the only somewhat reliable test is the spring back test with vise grips (preferrably needle nose visegrips) and a unfired virgin case and springback is entirely in the eye of the beholder.

They aren't (your handloads) blowing up in your face or exiting the cross drilled holes/vents in your receiver so I'm at a loss as to the cause for your bump issue...just say'in.

BTW, what caliber is this, you never alluded to that.

 

[dmax1800]

300 win mag.

 

[kraky2]

My sonic cleaner gets pretty warm and my shells are in for a while....not sure how you sonic clean. Any chance that and chemicals used could have an effect?

 

[dmax1800]

I always use the ultrasonic cleaner and same chemicals in the reloading process. This is the first I've had to shoulder bump problem. My conclusion is that the sonic cleaner or chemicals didn't cause the problem, but good question.