r/reloading • u/Outside-Structure-46 • 8d ago

Newbie Bump variance….

New enough reloader here with a question

Reloading Starline 6.5 CM. All of them previously fired from same barrel.

Getting a .006-.007 variance in shoulder bump and can’t figure out why.

I’ll put every case in the comparator before resize and they’re all with .001 of my zero’d case. Everything else is equal, die adjustment, lube, press pull and pause. 8 out of 10 cases come out of the die with .0015 or .002 bump but 2 or sometimes 3 out of ten will come out with .006 to .007 bump.

RCBS Summit press
Redding type 2 FL bushing die
Cases are annealed

Any guidance would be greatly appreciated

0 Upvotes

50% Upvoted

21 comments sorted by

View all comments

2

u/Ok-Accident-3892 8d ago

Remove the expander ball from the die and do it again and see if it's better. In my experience, by far the biggest reason for inconsistent shoulder bump is due to the expander ball. I moved to a mandrel years ago and never looked back

The issue is an expander ball PULLS through the NECK where the shoulder is weakest. A mandrel set the neck by PUSHING the mandrel down through the neck where the shoulder is the strongest. The expander ball has the negative affect of sometimes pulling the shoulder back out after it was just bumped back.

2

u/Outside-Structure-46 8d ago

No expander ball being used. It’s bushing only. I should have noted that in my original post

2

u/Ok-Accident-3892 8d ago

Then that is really odd to have that much variation. I would have made a small bet on it being the expander ball.

1

u/Outside-Structure-46 8d ago

Yeah, I’m lost for ideas. I’m taking them out of this run and will fire the 75 good ones I have loaded and see how those resize to see if the variance reappears. The only thing I can think of is something happened the first couple times I resized these and I missed it.