Head Space Help?

[MDslammer]

Hi Guys,

New to head space adjustments. I have the Hornady Head Gauge Kit. Using it for my .338 LM brass.
My measurement for once fired brass is coming out to 2.322".

I think I understand how to bump the should back by tweaking the FL resizing die down incrementally
until I get it to move to 2.322". Or do I set it to be less than that?

Also, some of my brass is a little shorter. 2.319" / 2.318". Is this OK to load being a bit shorter than the rest? If not, what are my options?

Thanks guys.

MDslammer
Las Vegas, NV

 

[mikecr]

The shorter cases are not fully fireformed yet.
You can set the bump 1-2thou under 0-headspace, whatever that turns out to be, when you get there.

Take care to creep into bumping with a FL die. You can easily go past productive bumping to actually pushing the shoulders forward(instead of back).
And be sure you're consistent with case lube, as this affects the result for each case.

 

[MDslammer]

HI Mikecr,

So if my fired cases are 2.322", I want to bump the shoulder back to 2.320" correct?
Also, can I still load and fire the shorter cases? i.e. 2.318" / 2.319"

Thanks.

Mark

 

[BoydAllen]

If you are working with once fire brass, I would first set your FL die to produce the same measurement as they came out of the chamber and then try them to see what the bolt close feels like. Depending on how hot the load was, you may have some clearance, and only need to reduce the diameter of the case body a little, without setting back the shoulder any. I would also check this shoulder to head dimension on all sized cases, because the same die setting will not give identical results, because of differences in annealing.

 

[MDslammer]

OK, thanks for the info Boyd.

 

[mikecr]

Boyd hit it.
You don't need to bump shoulders -until you need to. And then you can plan on doing so every reloading.

 

[clos]

HI Mikecr,

So if my fired cases are 2.322", I want to bump the shoulder back to 2.320" correct?

That I how I set up my dies. .002 under my once fire cases.



Also, can I still load and fire the shorter cases? i.e. 2.318" / 2.319"

You can do this, but you will stretch you case more.

Thanks.

Mark

 

[mikecr]

No, 2thou is too much for once fired cases, as they're likely a good bit off chamber shoulder still.
They aren't fully fire formed for three shots at least, and shouldn't present interference to bolt closure before this.

I say you shouldn't bump until you need to, because it's important to take cases to fully fireformed, which is stable, before sizing settings will hold in the long run.
If you start right off with FL sizing, before cases have reached any stable point, they may never reach it.
Then, with each premature/over sizing cycle, capacity variance grows.

 

[gotcha]

Mike's advise is spot on. One way to tell your cartridges are fully fire formed is increased resistance to bolt opening. This won't always be true for ALL the cartridges. Mark the cartridges that show resistance to opening and set your bump accordingly on those cartridges. Lock-in your die setting, the rest of the cartridges will soon catch up. Keep your press handle all the way down for a few extra seconds this will help the shoulder take a more uniform "set" to desired length. For me this works a little better than waiting for ALL the cartridges to exhibit the same amount of resistance to bolt opening.

 

[lpreddick]

remove the firing pin/spring and close the bolt on a fired case...if tight, push shoulder back by .001 until bolt closes with just the "right" amount of resistence. measure this case and bump the rest to same. sometimes a fired cases measurement is just right and no bumping needed.

 

[BoydAllen]

In my opinion, one should be careful to verify what is being done by feel by actual measurement with the correct tool. If a die is too large for the chamber it is paired with, case shoulders will be pushed back too far when working solely by feel. This will be detrimental to case life. I get that some have done it this way for years, but in offering the advice to do it that way to others, it seems to me that there is an assumption of the compatibility of the die with the chamber, which may not be the case. I have run into this situation more than once. Solving it involves getting a new, smaller die, or polishing out the chamber.