Embarrasing question: Bumping case shoulders

[gene pool]

I have a question that I am embarrassed to ask since so many people discuss doing it. Can anyone clearly explain how to "bump" case shoulders back just a little.

I am reloading 300 Win mag for precision shooting and would rather not full length resize fire-formed cases unless I have to. Normally I neck size only (Wilson bushing die) but every once in a while need to bump the necks back.

I have a Redding body die and a RCBS full length sizing die. Can I use the body die to do it? If so, how do I set the die?

Thanks in advance,
Gene Pool

 

[finnaddict]

Yes, it's basically set up just like a full length sizing die. Raise the ram with the shellholder in place. Lower the die to contact, lower the ram, turn the die 1/8 to 1/4 turn down further. The amount of turn past contact depends on the die, the brass, the press, etc... Just like a full length die.

If you're able to measure cases (base to shoulder datum) you can size minimally about 0.002 for bolt rifles. Use crappy cases that are of non shooting quality to experiment.


You want to adjust the body die to push the shoulder back the minimum amount. If you continually push the shoulder back further than you need to you will shorten your case life and can have a case head separation.

If you adjust the die to push the shoulder back just enough so that it will chamber with very little to no resistance, then you have adjusted your die to your chamber.

Set your rifle up on the bench and work the bolt to get a feel for the resistance you feel closing the bolt on an empty chamber.

Adjust the body die in until it hits the shell holder and lock it down. Size a case and try it in the rifle. It should have resistance to chambering.

Adjust the body die in a small amount, say 1/16 of a turn and size the case again. Try it in your rifle.

Continue doing this in very small increments until the crush fit when you chamber the case goes away. You want it to just barely go away.

It helps if you put witness marks on the die and press to keep track.

Don't forget to then neck size after you bump. Be sure to reajust the NS die so it does not push the shoulder back again.

 

[chris30br]

To be able to set the die to your chamber and size correctly it is best to be done with a striped bolt, no firing pin assy. Hard to feel 1/2 thou shoulder bump with firing pin installed. Just my opinion

 

[finnaddict]

To be able to set the die to your chamber and size correctly it is best to be done with a striped bolt, no firing pin assy. Hard to feel 1/2 thou shoulder bump with firing pin installed. Just my opinion

Knew I left something out. Thanks

 

[chris30br]

To be able to set the die to your chamber and size correctly it is best to be done with a striped bolt, no firing pin assy. Hard to feel 1/2 thou shoulder bump with firing pin installed. Just my opinion

Knew I left something out. Thanks

No problem. Good post

 

[jsthntn247]

Get one of these, put it on your calipers. Measure your fired cases then run them up in your die and gradually turn your die down until you measurement reads .001 less. Lock your die and your done. If you adjust your die down until it hits the shellholder and go down another 1/4 turn, you can be setting the shoulders back as much as .015 sometimes which really shortens brass life.
http://www.midwayusa.com/product/479704/hornady-lock-n-load-headspace-gage-5-bushing-set-with-comparator

 

[GSPV]

I use one of these:
http://forum.accurateshooter.com/index.php?topic=3797313.msg36129800#msg36129800 One of the two best purchases that I've made.

It's too hard-turning the die. Once you get close, use Skip Otto die shims. http://bulletin.accurateshooter.com/2013/03/sinclair-full-length-sizing-die-shims/

If you want to get totally pimp, you could get two shell holders a half-thou different and be able to predictably control the average/nominal bump. That doesn't mean that the real bump on every case will be that way.

 

[johnmyers]

Take out your firing pin and notice the bolt falls closed without a case in it. Start sizing a case and keep adjusting until you feel a little resistance on the last 1/4th of the bolt closing. Should be pretty close.

 

[GSPV]

It'll be close if the resistance is coming only from the shoulder. What if it's from somewhere else on the body?

And, guys, while I'm at it,

1. 1/16th of a turn is what? Right off the top of your head?

2. What happens when you find what you want, lock the ring down, then use a pair of pliars or whatever to get the die loose? Because, it will be tight.

I just don't want people to go through the frustrations that I have.

 

[KevinThomas]

For a 7/8x14 die, 1/16th of a turn should be about .004"-.005" more shoulder bump. Tiny adjustments, all that's needed, and it takes a light touch.

Gene, any reason you're not just F/L sizing on these cases? It'll likely save you some problems down the road, and they'll need to be F/L sized soon enough anyway. Just adjust the F/L dies as has been described here, headspacing on the shoulder (NOT the belt!) and bumping the shoulders back by only .001"-.002". This will give you the best of all worlds. Good case life, ease of chambering, match accuracy, etc..

 

[GSPV]

For a 7/8x14 die, 1/16th of a turn should be about .004"-.005" more shoulder bump. Tiny adjustments, all that's needed, and it takes a light touch.

Gene, any reason you're not just F/L sizing on these cases? It'll likely save you some problems down the road, and they'll need to be F/L sized soon enough anyway. Just adjust the F/L dies as has been described here, headspacing on the shoulder (NOT the belt!) and bumping the shoulders back by only .001"-.002". This will give you the best of all worlds. Good case life, ease of chambering, match accuracy, etc..

Yep. Nominally, it's 4.5 thou. Then there's the issue of what happens when you lock the die down and use pliars to get it loose. When you tighten that die back down, it's not going to go back to the witness mark you, hopefully, put on the die/press. It will pull up short. Too frustrating.

Die shims are too easy to use and too inexpensive not to have.

While I'm at it, I use seater die shims, too. Great way to accurately and repeatably change seating depth.

 

[DennisH]

I also use die shims. Too easy to use and all I want is .002 or maybe .001 neck tension.

They work great. You must measure the brass with every firing. You may be adding or taking away some shims

Dennis

PS: Not an embarrasing question, it's a very important process of reloading. If you go to this trouble, always check the concentricity of the bullet as well. I keep all mine under .002 and keep a special batch of brass that always seems to be near (0) when reloading. You may cull 50% of your bullets to obtain this!

Having a good barrel is a must. But it's worthless unless you have a good reloading process. Many may disagree with this, but John Hoover has made a believer out of me. Bullet/brass prep is a must.

Dennis

 

[gene pool]

Thank you all for the responses. They are understandable and provide good guidance.

One mentioned having a good barrel. My barrel is a Kreiger 17 twist MV (fluted deeply) on a Sako action. It's put together by a local smith who knows his stuff when it comes to building accurate rifles. The scope is Leupold 8.5x25x50 LR. I'm loading 77 grains of IMR 4350 behind a 110 grain Sierra HP. I've only fired about 50 rounds through it so far and am getting groups under 1/2". I'm confident if I can get the brass thing nailed down, the groups will be .3 or better. Don't ask why I'm tinkering with such a project. There is method to my madness.

Thank you again,
Gene Pool

 

[amlevin]

To be able to set the die to your chamber and size correctly it is best to be done with a striped bolt, no firing pin assy. Hard to feel 1/2 thou shoulder bump with firing pin installed. Just my opinion

I find that this process works best if you also remove the spring loaded ejector if used in your make of rifle. Absolutely nothing that will interfere with the "free float" of the bolt when a cartridge case is in the chamber. The ejector on a Remington Bolt can add resistance.