Resizing/shoulder bump problem

[ftrrookie]

I'm using Redding Competition "S" resizing die along with Redding competition shell holder set to resize/bump my brass. This equipment is new to me so I've followed Reddings directions on setting up and using these tools to the letter. And it's not working the way it had been explained that it would.

Just for clarity I'm resizing .308 win Lapua brass using the above die/shell holder in a RCBS rockchucker press.

Following directions I set up the die and the .010 shell holder. Run my brass in and no set back. That's how it should be. I then swap out the .010 holder for the .008 holder run the brass up again and still no set back. Not only that but some times the case actually stretches .001 - .0015". So it's actually longer at the datum line than when I started. Not at all what I expected. Now I switch to the .006 holder run the brass up and Viola! the shoulder is set back .002". Which is what I'm looking for. I guess what is confusing me is that I'm having to subtract .004" to get .002 in set back. Is this normal?
Or is there something I'm missing in my setup?

 

[kraky]

Welcome to the world of "toggling" press handles and what happens when you bump shellholders against the bottom of the die.
I rarely use my redding shellholders anymore.
In fact I've shaved some shellholders so they NEVER bump the bottom of the die.
I put a matching index mark on the die lockring and he threads of the die and make small tweaks either way to add or lose head space...it works very accurate as long as the shellholder isn't hitting the die.

 

[bigedp51]

When you first start resizing and "squeezing" the case, Newton's third law kicks in. When you squeeze the brass it has to move somewhere and that is upward and the case will "grow" in cartridge headspace length.

In the last few thousandths of ram movement the shoulder of the die is in contact with the shoulder of the case and making the case shorter. (shoulder bump) Which is up to you to control with your different height shell holders.

 

[CatShooter]

I'm using Redding Competition "S" resizing die along with Redding competition shell holder set to resize/bump my brass. This equipment is new to me so I've followed Reddings directions on setting up and using these tools to the letter. And it's not working the way it had been explained that it would.

Just for clarity I'm resizing .308 win Lapua brass using the above die/shell holder in a RCBS rockchucker press.

Following directions I set up the die and the .010 shell holder. Run my brass in and no set back. That's how it should be. I then swap out the .010 holder for the .008 holder run the brass up again and still no set back. Not only that but some times the case actually stretches .001 - .0015". So it's actually longer at the datum line than when I started. Not at all what I expected. Now I switch to the .006 holder run the brass up and Viola! the shoulder is set back .002". Which is what I'm looking for. I guess what is confusing me is that I'm having to subtract .004" to get .002 in set back. Is this normal?
Or is there something I'm missing in my setup?

When a full size die "Squeezes" the body of a fired case, before shoulder contact, the shoulder is not being touched, the shoulder does not stretch, it moves forward because the body is being constricted... this is 110% normal.

When the shoulder of the case hits the shoulder of the die, then the shoulder is pushed back to where you want it.

All of what you are experiencing is 110% normal.

Relax, be happy.

 

[bigedp51]

When a full size die "Squeezes" the body of a fired case, before shoulder contact, the shoulder is not being touched, the shoulder does not stretch, it moves forward because the body is being constricted... this is 110% normal.

When the shoulder of the case hits the shoulder of the die, then the shoulder is pushed back to where you want it.

All of what you are experiencing is 110% normal.

Relax, be happy.

catshooter

In baseball terms you lost the "squeeze play" by two minutes.

You might need to lube your fingers. :

 

[CatShooter]

I type slow !!

Meow

 

[6BRinNZ]

Just to confirm the confirmed have a read of this...

http://www.accurateshooter.com/technical-articles/die-issues-when-bumping-shoulders/

 

[CatShooter]

Hey Ed... what program do you use to make all those neat pictures?

 

[BoydAllen]

The illustration is wonderful, but I would suggest one change. "pressure ring" is a term that is already taken, and is pretty firmly established as a slight enlargement of a bullet's diameter at the base of the shank. This usage is virtually universal, this being one example.
http://www.matrixballistics.com/tech_info.html
Also, I would echo Catshooter's question. How did you do the illustration? It is a fine piece of work.

 

[GSPV]

Mike's bump gauge takes all the guesswork and pain out of setting bump:

http://forum.accurateshooter.com/index.php?topic=3797313.msg36129800#msg36129800

Combine it with a set of Skip's die shims and you're good to go.

 

[SmokinJoe]

+1 on the shims, and be sure to use the same shell holder each time. Shell holders can vary a lot in some critical dimensions. Shell holders are cheap, so I have a shell holder with each set of dies anymore.

 

[K22]

+1 on the shims, and be sure to use the same shell holder each time. Shell holders can vary a lot in some critical dimensions. Shell holders are cheap, so I have a shell holder with each set of dies anymore.

I adopted the same practice (years ago), a dedicated shell holder with each set of dies. Also, the various gauges available today take the guess work out of shoulder bumping to the desired degree.