Thread: Weird shoulder bump...

G'day team.

I may have solved the issue by getting some redding comp shell holders. But riddle me this anyway.

Loading for my 7mm08 using once fired Norma brass. FL sizing and started off with the die two turns out from the shell holder and turned it in 1/8 or so of a turn until the round chambers. Went a little bit more and felt good that I was measuring 2 thou shoulder bump. Over the next few cases this increased to 5 thou and stabilized. I tried again, and the same thing happened. I tried sorting cases so I was starting with the most consistent length possible. And the same thing happened. I cleaned the die out. And the same thing happened.

Where am I going wrong?

RCBS shell holder, redding FL die, imperial case lube, hornady press, redband gumboots etc. Anything else?

Does it chamber??? Stop measuring and problem goes away.

Originally Posted by Micky Duck

Does it chamber??? Stop measuring and problem goes away.

Ha! Knew that was coming. Yep it does, I was more worried about over working the brass, wherever that threshold lie.

Was your once fired brass either new brass or new factory ammo before it became once fired brass ?

Originally Posted by 30.06king

Was your once fired brass either new brass or new factory ammo before it became once fired brass ?

It was indeed new brass before it became once fired brass. Bought it new, loaded it up, fired it, and now it's once fired.

Originally Posted by Edunn

It was indeed new brass before it became once fired brass. Bought it new, loaded it up, fired it, and now it's once fired.

@Edunn
OK, this is what I think is happening.
Firstly, you're not doing anything wrong. And I don't think you are getting a wierd or variable shoulder bump. It's just being new brass some cases haven't stretched as much yet as they will after another firing or two.
Fired brass will conform to your rifle's chamber but being new ( relative to your actual chamber dimensions ) new brass doesn't always stretch to it's full extent until fired at least twice or maybe three times so, in fact, some shoulders are not being bumped just yet but at the moment give the impression of being over bumped. Also, it's possible that even your cases measuring longest to the shoulder now may not yet have stretched to their full limit but have just stretched a little more than other cases so far. So, be prepared to reset your FL die again at some point to give a true shoulder bump. It's possible that if left set where it is now you may be creating excessive headspace which can lead to both primer ignition issues and shortened case life.
What I suggest is that after the next couple of firings of your brass you reset the FL die for the ( true ) shoulder bump at which point the setting should become permanent and not require further resetting.
I say the above based on experience with FL sizing new 375 Ruger brass which had given nil ignition of some CCI primers and I was blaming the primers. I posted my situation here and some knowledgeable members pointed me in the right direction. I was simply over bumping the shoulders, creating excessive headspace, and when, as suggested, I backed the FL die out slightly it was "hey presto", problem solved.

Originally Posted by 30.06king

@Edunn
OK, this is what I think is happening.
Firstly, you're not doing anything wrong. And I don't think you are getting a wierd or variable shoulder bump. It's just being new brass some cases haven't stretched as much yet as they will after another firing or two.
Fired brass will conform to your rifle's chamber but being new ( relative to your actual chamber dimensions ) new brass doesn't always stretch to it's full extent until fired at least twice or maybe three times so, in fact, some shoulders are not being bumped just yet but at the moment give the impression of being over bumped. Also, it's possible that even your cases measuring longest to the shoulder now may not yet have stretched to their full limit but have just stretched a little more than other cases so far. So, be prepared to reset your FL die again at some point to give a true shoulder bump. It's possible that if left set where it is now you may be creating excessive headspace which can lead to both primer ignition issues and shortened case life.
What I suggest is that after the next couple of firings of your brass you reset the FL die for the ( true ) shoulder bump at which point the setting should become permanent and not require further resetting.
I say the above based on experience with FL sizing new 375 Ruger brass which had given nil ignition of some CCI primers and I was blaming the primers. I posted my situation here and some knowledgeable members pointed me in the right direction. I was simply over bumping the shoulders, creating excessive headspace, and when, as suggested, I backed the FL die out slightly it was "hey presto", problem solved.

Awesome, thanks mate! I wondered whether something like this might be the issue but the way you've laid it out makes sense. Just seemed weird that each time I set it at 2 thou for one case it ended up at about 5 thou for all of the rest of them. Will definitely be resetting the sizing die after this firing anyway but thought I'd troubleshoot now to make sure I'm not doing anything silly.

@Edunn when you set up your die did you use the same piece of brass each time you screwed the die further into the press?
I have read that that each time you screw the die in you should use a different piece of brass. If the same piece is used it work hardens and springs back more which gives the illusion that you have a .002" shoulder bump. The next piece of brass will spring back less because it has only been sized once. When you measured the second piece it may well have bumped back .005".

Yeah I set my shoulder bump by progressively adjusting the die after sizing and measuring different individual pieces of brass - only sizing each once. This means the first few until the die is set properly have a slightly different bump, but I don't really care.

Originally Posted by Tech

@Edunn when you set up your die did you use the same piece of brass each time you screwed the die further into the press?
I have read that that each time you screw the die in you should use a different piece of brass. If the same piece is used it work hardens and springs back more which gives the illusion that you have a .002" shoulder bump. The next piece of brass will spring back less because it has only been sized once. When you measured the second piece it may well have bumped back .005".

Crap - this is exactly my mistake. Thanks mate, this will be why I'm seeing the issue. Unfortunately I set my die and sized the next 50 pieces so they were all consistent but will know for the next firing, thankyou!

No not crap...and not a mistake...it's a learning experience.you now know for next time lol.

Originally Posted by Micky Duck

No not crap...and not a mistake...it's a learning experience.you now know for next time lol.

This is true. Suspect the brass may be a bit over worked but hopefully shouldn't cause any major problems.

Greetings @Edunn,
I think that the competition shell holders will give you a far more accurate setting than adjusting the die. There is a little spring in most presses and any round that sizes a bit hard is likely to be oversize. My limited experience with the 7mm-08 is that the chambers are close to minimum compared to the parent .308.
GPM.

Might be a good idea to anneal the brass now??

Originally Posted by Oldbloke

Might be a good idea to anneal the brass now??

Now? Or before next FL size?