Shoulder Bump

[cwood3]

Quick Disclaimer:

I'm on a project in Ulysses, Kansas for this week. Cold, boring, and have to occupy myself in the evenings. So I got to thinking about shoulder bump.

OK, I have a copy of Ratigan's book. In it he states that "shoulder bump" dies do not work. The case must be supported about the case diameter while pushing the shoulder down .0015 or so. Makes sense to me. OK, now let's say I have a piece of fired once brass. I measure the headspace,face to shoulder). Fire the same case a few times and discover it has lengthened a thou or so from the base to shoulder. Let's also say that with the FL die screwed down to where it makes contact with the shellholder, it does not bump the shoulder back at all.

It appears that there are 2 places where this can be taken care of, either at the face of the die, or the face of the shell holder. One needs to be machined a few thou or so. So what is everybody really doing to get the desired headspace length, without deforming the area where the shoulder meets the OD of the body of the case?

I got way too much time on my hands, so thanks.

cwood3

 

[dantiff2]

Redding already makes a,set) of shellholders in different thicknesses for this perpose

http://www.redding-reloading.com/pages/uniquely.html

Dan

 

[cwood3]

Dan,

I did see them in Sinclair's catalog. I figured that is what that was, but if you read the description, how it's worded, it's vague and misleading to me. Almost looks the opposite of what one is trying to achieve. However, I did just pop over to Redding's site and it included the phrase "decreases the headspace.....", etc. Now that makes perfect sense. Thanks for setting on the path to righteousness!

cwood3

 

[JoePellegrene]

So what is everybody really doing to get the desired headspace length, without deforming the area where the shoulder meets the OD of the body of the case?

Cutting .015 thousands off the bottom of you die will allow you to bump the shoulder, but may not support the case well enough, and it can bulge out when bumping the shoulder.

Order a Newlon die blank. Get a resize reamer that's .003 smaller than the body of your finish reamer. With the .003 sizing you'll get about .001 spring back, so you end up with the case having .001 clearance in the chamber.

Newlon Precision

 

[NorCalMikie]

Or, take 2 or 3 shell holders, chuck them upside down in a drill press, run them down on a oiled stone and take the amount of material off as needed. Got 2 with .003 and .005 removed. And the stone makes them looked like they were done at the factory.
Keep them marked so they don't get mixed up with the unturned.

 

[cwood3]

All good ideas. Actually, I don't mind springing for the Redding set of shell holders. Just money. And if money was a concern, I woulda never gotten bit by the Benchrest bug. I just want to make the best loads that I can. It may be just 1 of the things I can control. If I can just control my skills and abilities, I'll be happy.

 

[cwood3]

What would those be used for ?

 

[duanepa]

Longer, over spec. factory chambers.

 

[shepheard]

I have been using a Redding body die to bump my shoulders when they grow to long. After about 3 to 4 neck sizings they need to be bumped. Not sure if I am on the same page as you all.

 

[LRSmoke]

From Redding's website...

"To select the proper shellholder for your particular firearm’s chamber, start with the shellholder marked +.010. The shellholder should be adjusted to make firm contact with the bottom of the sizing die during the case sizing operation. Resize a case and try it,unprimed and empty) in the chamber of your firearm. If the empty case does not chamber or chambers with difficulty, switch to the shellholder marked +.008 and repeat the process. Stop at the shellholder that allows the firearm’s action to close freely. Your cases are now being sized properly to fit your chamber with a minimum amount of headspace."

In order for these shellholders to bump the shoulder back, instead of starting with your standard shellholder to set up your die, you start with the thickest shellholder that is +.010" to set up your die initially. After this, everytime you go to the next step thinner shellholder, you will be bumping the shoulder back another .002".