how much to bump shoulder

[ttfreestyle]

my new brass measures 2.194 with my shoulder comparator.
when it is once fired it measures 2.198

it shoots extremely well with the new brass, my question is how much should i bump the shoulder.
going back to new spec seems like a lot to me. thanks for any help

 

[jimbires]

I try to bump my shoulder back .002 Jim

 

[BoydAllen]

In my experience, it takes more than one firing for brass to reach its maximum head to shoulder measurement. I like to take one case and size it just enough to hold a bullet, not sizing the body, or bumping the shoulder, and load and shoot it 2-3 times. till its "headspace" measurement stabilizes, and then save it as a reference for future die settings for that barrel or, if not a switch barrel, rifle. If your new brass shoots well, I think that you should be even more pleased with how it does after it has been fired and reloaded, assuming that your die is a good fit for your chamber, which is the key. I have seen regular dies that did not size the base of a case, unless the shoulder had been bumped more than is a good idea for best case life. In those cases a custom die from Harrell's Precision solved the problem. He makes PPC, BR, and Dasher dies that are available in small increments of difference. Working with a well formed fired case from your chamber, he selects the size that is the best fit. Because the dies are on the shelf, the wait is minimal. The dies are cut with a boring bar on a CNC turning center, rather than with reamers. This allows for economical production of a wide variety of slight variations for each of the calibers that he makes dies for.

 

[fdshuster]

For a bolt-action I bump the shoulder back just enough for the bolt to close on the case, with just a little resistance, rarely more than .002". And because the headspace length will change/lengthen with each firing, as Boyd said, I take a fresh measurement after each firing using the Stoney Point gauge. Case life is a very long time & I cannot remember the last time I had the beginning of the bright ring indicating a pending case head seperation.

 

[ttfreestyle]

ok, i bumped the shoulder 2 thou. going to test tomorrow and see how it goes, the bolt still closes easy but i can tell the difference from the new brass.

 

[artbosco]

my new brass measures 2.194 with my shoulder comparator. when it is once fired it measures 2.198 it shoots extremely well with the new brass, my question is how much should i bump the shoulder?

No more than .002". I try for a little less than that.

 

[mikecr]

I agree with Boyd and Outdoorsman.
Don't go to first bumping until needed and save a reference case at the bench.
2Thou is a little too much bump for me. I try for 1thou and accept up to 1.5thou.
This, because I am seated off the lands with everything.

It is possible that fully fire formed brass falls out of tune for you. It has a little more H2o capacity, and the 'effective' seating distance w/resp to the lands is different from new brass(if bullets are not jammed). So load tweaks may be in order, but you will be in a more consistant condition than provided by new brass.